Risk factors for extra-axial hemorrhage during invasive monitoring using subdural electrodes

Risk factors for extra-axial hemorrhage during invasive monitoring using subdural electrodes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Risk factors for extra-axial hemorrhage during invasive monitoring using subdural electrodes Rofat Askoro, Kota Kagawa, Go Seyama, Akitake Okamura, Yasushi Orihashi, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8567785/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Apr, 2026 Read the published version in Neurosurgical Review → Version 1 posted 15 You are reading this latest preprint version Abstract Introduction Despite the increasing use of stereoelectroencephalography, subdural electrode (SDE) implantation remains valuable to identify the epileptogenic network. Extra-axial hemorrhage, including subdural and epidural, is one of the most frequent complications of SDE implantation. This study aimed to identify risk factors associated with extra-axial hemorrhage post–SDE implantation in patients with focal drug-resistant epilepsy. Methods We retrospectively reviewed consecutive patients who underwent SDE implantation via craniotomy at Hiroshima University Hospital between 2008 and 2022. Multivariate logistic regression analysis was performed to identify risk factors for postoperative extra-axial hemorrhage. Results A total of 64 patients were included in the analysis; 13 of them had extra-axial hemorrhage after SDE implantation, and two required hematoma evacuation. The hematoma thickness increased over time in 7 of 11 patients who did not undergo surgical intervention. Univariate analysis revealed that extra-axial hemorrhage was associated with the number of electrodes (p = 0.0138), the number of leads (p = 0.0320) and selection of an artificial dura substitute (p = 0.0087). In multivariate analysis, the use of an absorbable artificial dura substitute for duraplasty (OR = 7.69, 95% CI: 2.39–24.72, p = 0.0006) was independent risk factors for post-implantation extra-axial hemorrhage. Conclusion The use of an absorbable artificial dura substitute for duraplasty is associated with the occurrence of extra-axial hemorrhage after SDE implantation. The risk of this complication can be minimized through careful selection of dura substitute materials. Close observation is essential during SDE implantation because an extra-axial hematoma may develop over time. subdural electrodes extra-axial hemorrhage adverse events epilepsy surgery dura substitute Figures Figure 1 Figure 2 Figure 3 Introduction Surgical resection of the epileptogenic zone remains a key treatment option for focal drug-resistant epilepsy to achieve a seizure-free outcome [ 1 ]. The success of epilepsy surgery primarily depends on the accurate localization of the epileptogenic zone or network through presurgical evaluation [ 2 ]. Concordant findings from seizure semiology, imaging findings, and scalp video-electroencephalography (EEG) may be sufficient to proceed with surgical resection [ 3 ]. However, in patients with inconclusive or discordant findings, invasive intracranial EEG monitoring is commonly required to better delineate the seizure network [ 4 , 5 ]. Traditionally, subdural electrodes (SDEs) have been predominantly used for invasive monitoring, especially in North America, the United Kingdom, Germany, and Japan [ 6 ]. However, with the advent of stereotactic techniques and robot-assisted surgery, stereoelectroencephalography (SEEG) has gained wider adoption [ 7 – 9 ] because of its several advantages, namely, minimal invasiveness, a lower risk of postoperative complications, easier multilobar or bilateral implantations, and the ability to record from superficial and deep brain structures [ 6 , 10 ]. Nevertheless, SDE implantation via craniotomy is still indicated in specific contexts by providing broad cortical coverage and enabling high-resolution functional mapping, particularly in those with perirolandic or eloquent cortex involvement [ 11 , 12 ]. The potential benefits of invasive monitoring with SDE implantation generally outweigh the risk of adverse events during the implantation procedure and subsequent EEG monitoring [ 13 , 14 ]. Hemorrhage, infections, and elevated intracranial pressure have been reported as potential complications of SDE implantation [ 7 ]. A systematic review identified extra-axial hemorrhage, including subdural and epidural, as the most common complication of invasive monitoring using SDEs [ 13 ]. To date, only few studies have explored the risk factors associated with extra-axial hemorrhage. Therefore, this study aimed to identify clinical and surgical variables associated with extra-axial hemorrhage during invasive monitoring using SDEs. Improved understanding of the risk factors may enhance clinical decision-making and SDE implantation safety. Materials & Methods Patients We retrospectively reviewed the medical records and operative notes of consecutive pediatric or adult patients with drug-resistant epilepsy who underwent intracranial video EEG monitoring using SDEs via craniotomy from October 2008 to September 2022 at the Department of Neurosurgery, Hiroshima University Hospital. Since 2022, a surgical robot system for SEEG has been introduced in our hospital; hence, only patients before this adaptation were included. The Ethical Committee for Clinical Research of Hiroshima University approved this study (approval number: E2025-0017). Indication and Presurgical Evaluation Invasive monitoring indicated for each patient was determined based on the comprehensive presurgical evaluation. All patients had previously undergone scalp video-EEG monitoring, computed tomography (CT), magnetic resonance imaging (MRI), Wada test, neuropsychological testing, magnetoencephalography (MEG), fluorodeoxyglucose-positron emission tomography (FDG-PET), and iomazenil-single-photon emission computed tomography (IMZ-SPECT). The implantation sites and number of subdural grid and strip electrodes were carefully selected based on seizure semiology, EEG findings, and imaging results. In some patients, depth electrodes were also utilized. Besides assessing the presumed epileptogenic zone, SDEs were also implanted for mapping the eloquent cortex when needed. Implantation Procedure A platinum subdural grid electrode and strip electrodes were used for SDE implantation (Unique Medical, Tokyo, Japan). Depth electrodes were used when required. The available electrode configurations were 8×8, 4×8, 2×8, or 2×4 for grid electrodes and 1×6 or 1×4 for strip electrodes, with an interval of 1 cm between each electrode. Depending on the case, the unused parts of the grid electrode were trimmed to fit the brain surface coverage area. The depth electrode consisted of six contacts with a 1-cm interval. Skin incision and craniotomy size were carefully estimated to create an adequate opening for the operative field and cortical coverage area for SDE implantation. SDEs were placed directly on the exposed brain surface under visualization or slid into the brain surface under X-ray fluoroscopy. A free-hand neuronavigation-guided technique using the Curve™ neuronavigation system was applied for depth electrode insertion (Brainlab AG, Munich, Germany). A pointer with reflective spherical markers was directly punctured into the brain and manually inserted along the planned trajectory under the neuronavigation system. After reaching the desired depth of target, the pointer was removed, and the depth electrode was manually inserted through the previous route from the pointer. Post-implantation, duraplasty was performed using either an absorbable or a non-absorbable dura substitute. Dura substitutes were trimmed to fit the dural defect shape. In our study, Seamdura® (Gunze, Kyoto, Japan), an absorbable dura material made of poly-L-lactide copolymer and ɛ-caprolactone copolymeric film layered with polyglycolic acid (PGA), and Gore-Tex® (W.L. Gore & Associates, Flagstaff, AZ, USA), a non-absorbable dura made from expanded polytetrafluoroethylene (ePTFE), were used, which are widely available in Japan. Gore-Tex was initially used for duraplasty after SDE implantation. In 2010, Seamdura was introduced because its translucency allowed direct visualization of any positional shift of the SDE after duraplasty. The dura substitute was sutured to the native dura using a synthetic, non-absorbable braided suture (Nurolon®, Johnson & Johnson, Somerville, NJ, USA). Electrode leads were routed subcutaneously and sutured to the skin using a nylon suture to prevent positional shift. The autologous bone flap was fixed back, and adequate dural tenting was performed. Dural, galeal, muscular, and skin bleeding were sufficiently coagulated by applying bipolar electrocautery. Between October 2008 and September 2022, each surgery was performed by a team of two or three operators drawn from four attending neurosurgeons: Takeshi Nishimoto (worked from October 2008 to March 2012), K.K (worked from October 2008 to March 2016 and from July 2017 to September 2022), Masaya Katagiri (worked from April 2011 to August 2017 and from April 2019 to September 2022), and G.S. (worked from April 2016 to September 2022). All four operators were well-trained neurosurgeons with 7–11 years of experience at the time of their arrival. Postoperative Protocol All patients underwent an immediate postoperative head CT scan following SDE implantation and a routine repeat scan on postoperative day 1. Intracranial video EEG monitoring was started on day 1 and continued until the number of captured ictal recordings was sufficient under a tapered antiseizure medication. Additional CT scans were performed if any clinical signs suggestive of complications were observed during the monitoring period. Post-monitoring, a head CT scan was routinely performed. Electrical stimulation was performed to map out the eloquent area when required. Prophylactic antibiotics were administered intravenously or orally throughout the SDE implantation period. The subsequent surgery for electrode removal was prescheduled based on the duration required for scalp video-EEG monitoring. Cortical resection was performed at the time of electrode removal as indicated. Definition of Complication Complications were defined as follows: (1) any neurological deficit occurring from electrode placement to removal; (2) any clinical events requiring surgical intervention; (3) infections occurring during the monitoring period until electrode removal; (4) abnormalities detected on head CT scan, including postoperative intracerebral, subdural and epidural hemorrhage. For extra-axial hemorrhage, a high-density lesion on axial CT scan with a thickness of ≥ 1 cm was considered a complication, regardless of the presence or absence of any symptoms. Infections occurring after electrode removal or resective surgery were not included. The cause of each complication was thoroughly investigated, including the presence of any technical problems. For extra-axial hemorrhage, statistical analysis was performed to identify possible risk factors. Data Collection The following data were collected as potential risk factors for the occurrence of extra-axial hemorrhage: age at surgery, sex, seizure duration, seizure type, the presence of MRI lesions, the number of antiseizure medications (ASMs), hemoglobin (Hb), platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), laterality of electrode placement (unilateral vs bilateral placement), maximum grid size (33–64 electrodes vs 8–32 electrodes), total number of electrodes, total number of leads, use of depth electrodes, maximum craniotomy diameter and depth, selection of an artificial dura substitute (Gore-Tex vs Seamdura), and surgical duration. The craniotomy diameter and depth were retrospectively measured on an axial or coronal image of the postoperative CT scan (Fig. 1 ). Seizure outcome was evaluated at 2 years postoperatively using the Engel classification [ 15 ]. Statistical Analysis for Extra-axial Hemorrhage Statistical analysis was performed using JMP 18 (SAS Institute Inc.). The incidence of extra-axial hemorrhage, regardless of symptoms, was considered as the outcome of interest (dependent variable). Independent variables included in the model were as follows: age at surgery, sex, seizure duration, seizure type, presence of MRI lesions, number of ASMs, Hb, platelet count, PT, APTT, laterality of electrode placement (unilateral vs bilateral hemisphere), maximum grid size (33–64 electrodes vs 8–32 electrodes), total number of electrodes, total number of leads, use of depth electrodes, maximum craniotomy diameter and depth, selection of an artificial dura substitute, and surgical duration. Univariate analyses were performed using Pearson’s chi-square test for categorical variables and the Mann-Whitney U-test for continuous variables. Variables with p < 0.5 in the univariate analysis were included in the multivariate logistic regression analysis to determine risk factors for extra-axial hemorrhage. The least absolute shrinkage and selection operator (LASSO) regression was applied to stabilize model estimation in the multivariate analysis. Odds ratios with 95% confidence intervals (CI) and p-values were calculated, and p < 0.05 was considered statistically significant. Results Patient Characteristics A total of 64 patients were included in this study. Table 1 presents the summary of patient demographics and clinical characteristics, including postoperative complications. The median age at the time of surgery was 29 (range: 1–63) years, and the median duration of epilepsy was 16 (range: 1–49) years. MRI findings detected no lesion in 38 patients (59.3%). Focal-impaired awareness seizure (FIAS) and focal to bilateral tonic–clonic seizure (FBTCS) were observed in 30 (46.8%) and 9 (14.1%) patients, respectively, and a combination of FIAS and FBTCS was observed in 13 (20.3%) patients. Focal-onset motor seizures occurred in nine (14.1%) patients. Sixteen patients (25.0%) had complications related to SDE implantation, with the most common being the presence of extra-axial hemorrhage, including subdural and epidural. No incidence of intracerebral hemorrhage was observed. Of the 16 patients, surgical intervention was required in five patients (7.8%). No permanent neurological deficits were observed in all patients with complications. Resective surgery was required in 60 (93.8%) patients after an invasive monitoring period. An Engel class I outcome was achieved in 36 patients at 2 years postoperatively. Engel class II and III outcomes were achieved in 10 and 9 patients, respectively. Five patients remained in the Engel class IV category. Table 1 Demographic data and clinical characteristics Characteristics Value Age (median, range) 29 (1–63) Sex distribution (male : female) 37 : 27 Seizure duration (years) (median, range) 16 (1–49) MRI lesion Detected Undetected 26 38 Number of antiseizure medications (median, range) 3 (1–5) Seizure type: FIAS FBTCS FIAS + FBTCS FMS Other 30 9 13 9 3 Postoperative complications * Extra-axial hemorrhage Intracerebral hemorrhage Infection Increased intracranial pressure due to tight duraplasty Brain edema due to venous compression Electrode malfunction 13 (2) 0 0 1 (1) 1 (1) 1 (1) Seizure outcome (Engel Classification) I II III IV No further resective surgery 36 10 9 5 4 FIAS = focal impaired aware seizure; FBTCS = focal to bilateral tonic-clonic seizure; FMS: focal onset motor seizure. *The number of patients who required surgical intervention is given in parentheses. Surgical Factors SDEs were implanted in the unilateral and bilateral hemispheres in 41 and 23 patients, respectively. Thirty patients had a subdural grid with a size of ≥ 33 contacts. The median number of total electrodes was 98 (range: 32–136). Depth electrodes were used in 52 patients, in which the number of leads of depth electrodes ranged from 1 to 4. The median craniotomy diameter was 113.77 (range: 78.64–142.31) mm. The selection of artificial dura substitutes is shown in Fig. 2 . Seamdura was first introduced in 2010 and used more frequently than Gore-Tex between 2011 and 2015. In all other years, Gore-Tex remained the predominant material used. Characteristics of Patients with Extra-axial Hemorrhage Thirteen patients (20.3%) experienced extra-axial hemorrhage, the most common complication after SDE implantation. The patient characteristics are summarized in Table 2 . Of the 13 patients, two underwent emergency surgical intervention for hematoma removal due to considerable neurological symptoms. One patient (patient no.7 in Table 2 ) experienced severe nausea, vomiting, and headache, and these symptoms worsened. A CT scan on postoperative day 1 revealed signs of brain parenchymal compression due to an extra-axial hematoma, requiring emergency hematoma removal. During hematoma removal, persistent bleeding was evident from the edge of the dural incision. The other patient (patient no. 9 in Table 2 ) developed a gradually worsening headache and confusion during the video-EEG monitoring. CT scan on postoperative day 7 revealed a thick extra-axial hematoma and brain compression, needing emergency hematoma removal. Both patients fully recovered from the symptoms after hematoma removal. In the remaining 11 patients who did not develop notable symptoms, their postoperative course was managed with close monitoring. In 13 patients with extra-axial hemorrhage, the hematoma location was above the subdural electrodes in 12 patients. Seamdura was used in nine patients, whereas Gore-Tex was used in four patients. The thickness of the hematoma increased over time in 7 of 11 patients who did not undergo surgical intervention. No patient with extra-axial hemorrhage developed cerebral contusion or vascular injury, which was confirmed upon subdural electrode removal. Table 2 Characteristics of patients with extra-axial hemorrhage complication. Case no. Age (yrs) / Sex Duration of implantation (days) Hemorrhage thickness changes from day 1 → latest (cm) Hematoma location (relative to electrode) Hematoma type Maxiumum craniotomy diameter (mm) Dura substitute at implantation Surgical intervention Interval from implantation to evacuation surgery (days) Subsequent resection site Seizure Outcome (Engel Class) 1 33/M 12 < 1 → 1.8 Under SDH 135 Gore-Tex None — Lt. T I 2 52/F 17 1.1 → 1.1 Above SDH, EDH 128.1 Gore-Tex None — Lt. T I 3 39/F 17 1.0 → 1.0 Above SDH, EDH 123.4 Seamdura None — Rt. F T I 4 32/M 21 1.1 → 1.8 Above SDH 100.1 Seamdura None — Lt. T II 5 46/F 25 < 1 → 1.5 Above SDH, EDH 115.6 Seamdura None — Lt. T I 6 28/M 19 < 1 → 1.0 Above SDH 85.9 Seamdura None — Rt. F T IV 7 14/F 22 1.8 (removed) Above SDH 114.4 Seamdura Hematoma removal 1 Rt. F I 8 41/M 22 < 1 → 1.3 Above SDH, EDH 133.8 Seamdura None — Lt. F I 9 15/F 7 < 1 → 2.5 (removed) Above SDH 138.9 Seamdura Hematoma removal 7 Rt. F IV 10 63/F 21 < 1 → 1.3 Above SDH, EDH 106.3 Seamdura None — Rt. T II 11 53/M 14 1.4 → 1.4 Above SDH 130.2 Gore-Tex None — Lt. C P I 12 47/M 14 1.0 → 1.0 Above SDH, EDH 107.1 Seamdura None — Rt. hemisphere I 13 19/M 15 < 1 → 1.1 Above SDH, EDH 125.1 Gore-Tex None — Rt. P I SDH = subdural hematoma; EDH = epidural hematoma; Lt. = left; Rt. = right; F = frontal; T = temporal; P = parietal; C = central. Engel class indicates seizure outcome at 12-month follow-up. “—” indicates no surgical intervention was required. Other Complications Other complications are listed in Table 1 . Intracranial pressure increased in one patient owing to tight duraplasty, which resolved after decompression. One patient underwent emergency surgical intervention on postoperative day 1 due to left hemiparesis. The CT scan revealed cerebral edema in the right hemisphere. Intraoperatively, electrode leads were found to be compressing a cortical vein near the primary motor cortex. The leads were replaced with smaller electrodes and repositioned, resulting in clinical condition improvement. Another patient experienced electrode damage from a hyperkinetic seizure, requiring emergency replacement of the electrode. All patients who required surgical intervention for complications recovered without permanent neurological deficits. Univariate and Multivariate Analysis for Extra-axial Hemorrhage Univariate analysis revealed that postoperative extra-axial hemorrhage was significantly associated with a higher number of electrodes (p = 0.013), higher number of leads (p = 0.032), and use of Seamdura (p = 0.008; Table 3 ). No patient-specific variables were significantly associated with the extra-axial hemorrhage. Table 3 Univariate analysis for the risk of extra-axial hemorrhage during invasive recording. Variable Control group (n = 51) Extra-axial hemorrhage (n = 13) P value Patient-specific factor Age at surgery, years 28 (1–59) 39 (14–63) 0.0518 Sex: Male Female 30 21 7 6 0.7627 Presence of MRI lesion 23 3 0.2102 No. of ASMs 3 (1–5) 3 (1–5) 0.8086 Hemoglobin 13.2 (4.3–16.7) 13.2 (11.5–16.1) 0.8216 Platelet count 240 (108–457) 209 (152–383) 0.2893 PT time 11.7 (10–13.1) 11.5 (10–12.9) 1.0000 APTT 29.95 (21.4–35.3) 28.8 (25–39.3) 0.8368 Surgery-specific factor Laterality of electrode placement: Unilateral Bilateral 36 15 5 8 0.0505 Maximum grid size: 8–32 33–64 27 24 7 6 1.0000 Number of electrodes 96 (32–136) 110 (96–132) 0.0138* Number of leads 11 (4–18) 13 (10–17) 0.0320* Use of depth electrodes 43 9 0.2431 Maximum craniotomy diameter (mm) 111.35 (78.64–142.31) 123.44 (85.94–138.97) 0.0735 Maxiumum craniotomy depth (mm) 17.79 (6.41–31.24) 21.7 (7.1–33.8) 0.4903 Artificial dura material: Gore-Tex Seamdura 37 14 4 9 0.0087* Surgical duration (minutes) 422 (279–720) 442 (356–648) 0.5991 ASM = antiseizure medications, PT = prothrombin time, APTT = activated partial thromboplastin time Four variables were selected using the LASSO approach in the multivariate analysis (Table 4 ). The analysis identified the use of Seamdura as an artificial dura substitute as independent risk factor of extra-axial hemorrhage than the use of Gore-Tex (OR = 7.69, 95% CI: 2.39–24.72, p = 0.0006). The remaining variables including age at surgery, number of electrodes, and maximum craniotomy diameter did not significantly demonstrate the predictive risk for extra-axial hemorrhage. Table 4 Multivariate analysis for the risk of extra-axial hemorrhage during invasive monitoring. Variable OR 95% CI P value Age at surgery, years 1.02 0.97–1.08 0.3404 Number of electrodes 1.02 0.99–1.05 0.1026 Maximum craniotomy diameter 1.03 0.98–1.08 0.1651 Artificial dura material (Seamdura) 7.69 2.39–24.72 0.0006* Discussion Summary of Results This retrospective study analyzed the complications following SDE implantation for intracranial video-EEG monitoring and identified the risk factors associated with extra-axial hemorrhage in 64 patients with drug-resistant epilepsy. Thirteen (20.3%) patients developed extra-axial hemorrhage on CT scan after SDE implantation. Multivariate analysis identified the use of Seamdura as the artificial dura substitute as the independent predictive factors for extra-axial hemorrhage. Other complications in our series consisted of elevated intracranial pressure due to tight duraplasty, brain edema secondary to venous compression by the implanted electrode lead, and electrode malfunction due to hyperkinetic seizures. Common complications, such as intracerebral hemorrhage and infections, reported in previous studies were not observed in our cohort. Although unplanned emergency surgical intervention was performed for two patients with extra-axial hemorrhage and three with other complications, no patients experienced permanent neurological deficits or death. Hemorrhagic Complications Following SDE Implantation Previous studies have documented symptomatic hemorrhagic complications following SDE implantation in pediatric and adult patients, with reported rates between 1.4% and 11% [ 6 , 16 – 22 ]. However, hemorrhagic complication rates increase to 16–38% when considering imaging-only hemorrhages [ 19 , 21 ]. Extra-axial hemorrhage, including subdural and epidural, has been reported as the most common form of hemorrhagic complications [ 13 , 23 ]. A previous systematic review reported that among 2036 patients, the incidences of extra-axial hemorrhage and intracerebral hemorrhage were 3.4% and 1.4%, respectively [ 23 ]. Subdural hemorrhage is reported as the most predominant among extra-axial hemorrhages [ 13 ]. Thirteen patients (20.3%) in our cohort had extra-axial hemorrhage on CT scan, which is comparable with those of previous reports. Risk Factors for Extra-axial Hemorrhage The cause of extra-axial hematoma formation without intraoperative bleeding is still not fully understood [ 13 , 14 , 19 , 24 ]. Lee et al. reported that delayed subdural hematoma formation is one of the major complications, in which the hematoma showing progressive enlargement within 3 days after SDE insertion [ 24 ]. Previous studies have indicated that the number of electrode contacts or the size of grids influences the likelihood of hemorrhagic complications [ 13 , 19 , 25 ]. Specifically, 67 or more electrode contacts [ 13 ] and the use of grids with 64 contacts [ 19 ] have been reported as risk factors. In our case series, the use of an absorbable dura (Seamdura) have been identified as independent risk factors for extra-axial hemorrhage. Hematomas were more frequently located outside the SDE rather than beneath it. In some cases, the size of the hematoma gradually increased over a week. No findings of cerebral contusion or vascular damage were observed in any patient with extra-axial hemorrhage. These observations indicate that bleeding from the edge of the dural incision plays a major role in extra-axial hematoma formation. Despite achieving adequate dural hemostasis using standard bipolar coagulation during surgery, postoperative rebleeding may occur [ 26 ]. Because the dural suture line lies between SDE and the bone flap, no living tissue comes into contact with the suture site, which could create an environment that could hinder wound healing at the edge of the dural incision. The use of Seamdura (absorbable dural substitutes) was notably associated with extra-axial hemorrhage in our study, a finding not previously discussed in the literature. Several differences exist between Gore-Tex (non-absorbable dural substitute) and Seamdura (absorbable substitute), as summarized in Table 5 : (1) Regarding transparency, Gore-Tex is opaque, whereas Seamdura is translucent and can be easily trimmed to fit the shape of the dural defect. SDE can be observed through Seamdura even after dural closure. (2) Seamdura is a weaker material than Gore-Tex. Matsumoto et al. reported that Seamdura has lesser suture point strength compared to Gore-Tex, which further decreases after 48-hour incubation [ 27 ]. (3) Gore-Tex has higher pliability than Seamdura. When a surgeon grasps any part of the artificial dura with tweezers, Gore-Tex can be easily pleated, whereas Seamdura can flatten and not be pleated as easily. Among these differences, we considered material strength and pliability to have the greatest influence on extra-axial hemorrhage formation (Fig. 3 ). While a stronger material of Gore-Tex allows application of a tight suture between the artificial dura and the edge of the dural incision, a weaker material of Seamdura may cause artificial dural tearing. The easy-pleating property of Gore-Tex allows it to adhere closely to the edge of the dural incision, thereby minimizing bleeding from the incision edges. Our results indicate the influence of selecting the artificial dura substitute on the risk of developing extra-axial hemorrhage. Gore-Tex is preferred over Seamdura for duraplasty during SDE implantation to prevent extra-axial hemorrhage. Table 5 Characteristics of dura substitute Characteristics Gore-Tex Seamdura Materials Expanded polytetrafluoroethylene (ePTFE) Poly-L-lactide copolymer and ɛ-caprolactone copolymeric film layered with polyglycolic acid (PGA) Opacity Opaque Translucent Pliability More pliable and flexible Less pliable compliant Material strength 27 Higher Lower Other Complications and the Future of SDE Implantation As complications other than extra-axial hemorrhage, elevated intracranial pressure owing to tight duraplasty and brain edema secondary to venous compression by the implanted electrode lead were observed. Both complications were attributed to technical factors. We did not recognize these issues during electrode implantation; however, the cause of the former was noted through postoperative CT and the latter during reoperation. This feedback was applied in subsequent surgeries, and the same mistakes were not repeated. Previous studies also indicated that increasing procedural experience can reduce SDE-related complications over time [ 18 , 28 ]. One patient underwent surgical intervention for electrode malfunction caused by hyperkinetic seizures. Such complications can occur with invasive monitoring using SDE and SEEG in patients with focal hyperkinetic seizures or generalized seizures. Appropriate case selection and careful monitoring are necessary. We had no cases of infection, which may be attributed to the continued administration of antibiotics while SDEs were in place. Infections occurring after electrode removal and focal cortical resection were not included in this study. In summary, all SDE-related complications in our series occurred in the extra-axial space, which contrasts with complications from depth electrode insertion for SEEG. SEEG-related hemorrhages are predominantly intra-axial cerebral hemorrhages [ 23 , 29 ] and intracerebral hemorrhage that may cause permanent neurological deficits [ 30 ]. In contrast, for problems occurring outside the brain, prompt and timely surgical intervention can prevent permanent neurological deficit. Although surgical intervention was required in five patients in our series, no permanent neurological deficits or deaths were reported. Although SDE implantation is clearly more invasive than SEEG, with high operator skill and careful observation during SDE implantation, it may decrease the permanent complication rate compared to SEEG. As the field moves toward a paradigm shift from SDE to SEEG, maintaining the skills of SDE implantation is an important issue. Limitation The current study has several limitations. The retrospective, single-center design and the small sample size limit the associations identified in the results. Although the surgical procedure and postoperative protocol remained unchanged during the study period, potential factors may have been influenced by the passage of time. For example, the learning curve for surgeons’ skills is difficult to assess. Our preference for the selection of an artificial dura substitute changed over time. The artificial dura substitutes examined (Seamdura and Gore-Tex) are commonly used in Japan, and their availability may differ in other regions, further limiting external applicability. Different absorbable artificial dura products may exhibit different properties. Future multicenter prospective studies with standardized imaging protocols and broader material comparisons are needed to validate and generalize our findings. Conclusion Selection of an artificial dura substitute in duraplasty contributes to extra-axial hemorrhage after SDE implantation. The use of an absorbable dura was associated with a higher risk of extra-axial hemorrhage. The use of non-absorbable dura substitutes with high pliability and superior mechanical stability is recommended to prevent extra-axial hemorrhage after SDE implantation. Because extra-axial hematoma may grow over time, careful observation is essential during SDG implantation. Declarations Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Disclosure of Conflict of Interest The authors declare no relevant financial or non-financial interest regarding the production of this article. Author contributions Rofat Askoro: study design; data curation; data analysis; interpretation of results; writing original draft; visualization. Kota Kagawa: writing and review final draft; validation; supervision; data analysis; conceptualization; project administration. Go Seyama : methodology; validation; data curation; writing—review & editing; investigation. Akitake Okamura : writing—review & editing; validation; investigation; data curation. Yasushi Orihashi : writing—review & editing, validation, data analysis; methodology; interpretation of results. Ayako Takamori : writing—review & editing, validation, data analysis; methodology; interpretation of results. Nobutaka Horie : writing—review & editing; validation; supervision. Ethics Approval Statement This study was approved by The Ethical Committee for Clinical Research of Hiroshima University (approval number: E2025-0017). We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Patient Consent This study implemented an opt-out arrangement by providing necessary information for informed decision and adequate measures to anonymize medical information and images in accordance with Hiroshima University Hospital policy. Clinical Trial Number Not applicable. 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J Clin Neurosci 53:132–134. https://doi.org/10.1016/j.jocn.2018.04.064 Gavvala J, Zafar M, Sinha SR, Kalamangalam G, Schuele S, Consortium AS et al (2022) Stereotactic EEG practices: A survey of united states tertiary referral epilepsy centers. J Clin Neurophysiol 39:474–480. https://doi.org/10.1097/Wnp.0000000000000794 Maesawa S, Ishizaki T, Mutoh M, Ito Y, Torii J, Tanei T et al (2023) Clinical impacts of stereotactic electroencephalography on epilepsy surgery and associated issues in the current situation in japan. Neurol Med Chir (Tokyo) 63:179–190. https://doi.org/10.2176/jns-nmc.2022-0271 Gomes FC, Larcipretti ALL, Udoma-Udofa OC, Rocha BAA, Mota MEB, Decina MM et al (2025) Stereoelectroencephalography versus subdural electrodes for invasive monitoring of drug-resistant epilepsy patients: A systematic review and meta-analysis. Seizure 129:33–41. https://doi.org/10.1016/j.seizure.2025.04.001 Mullin JP, Sexton D, Al-Omar S, Bingaman W, Gonzalez-Martinez J (2016) Outcomes of subdural grid electrode monitoring in the stereoelectroencephalography era. World Neurosurg 89:255–258. https://doi.org/10.1016/j.wneu.2016.02.034 Kerezoudis P, Lundstrom BN, Meyer FB, Worrell GA, Van Gompel JJ (2022) Surgical approaches to refractory central lobule epilepsy: A systematic review on the role of resection, ablation, and stimulation in the contemporary era. J Neurosurg 137:735–746. https://doi.org/10.3171/2021.10.JNS211875 Arya R, Mangano FT, Horn PS, Holland KD, Rose DF, Glauser TA (2013) Adverse events related to extraoperative invasive EEG monitoring with subdural grid electrodes: A systematic review and meta-analysis. Epilepsia 54:828–839. https://doi.org/10.1111/epi.12073 Wellmer J, von der Groeben F, Klarmann U, Weber C, Elger CE, Urbach H et al (2012) Risks and benefits of invasive epilepsy surgery workup with implanted subdural and depth electrodes. Epilepsia 53:1322–1332. https://doi.org/10.1111/j.1528-1167.2012.03545.x Engel J Jr., Van Ness P, Rasmussen T, Ojemann LM (1993) Outcome with respect to epileptic seizures. In: Engel J, Jr. (ed) Surgical Treatment of the Epilepsies, 2 edn. Raven, New York, NY, pp 609–621 Jehi L, Morita-Sherman M, Love TE, Bartolomei F, Bingaman W, Braun K et al (2021) Comparative effectiveness of stereotactic electroencephalography versus subdural grids in epilepsy surgery. Ann Neurol 90:927–939. https://doi.org/10.1002/ana.26238 Joswig H, Lau JC, Abdallat M, Parrent AG, MacDougall KW, McLachlan RS et al (2020) Stereoelectroencephalography versus subdural strip electrode implantations: Feasibility, complications, and outcomes in 500 intracranial monitoring cases for drug-resistant epilepsy. Neurosurgery 87:E23–E30. https://doi.org/10.1093/neuros/nyaa112 Lee AT, Nichols NM, Speidel BA, Fan JM, Cajigas I, Knowlton RC et al (2023) Modern intracranial electroencephalography for epilepsy localization with combined subdural grid and depth electrodes with low and improved hemorrhagic complication rates. J Neurosurg 138:821–827. https://doi.org/10.3171/2022.5.Jns221118 Männlin J, San Antonio-Arce V, Reinacher PC, Scheiwe C, Shah MJ, Urbach H et al (2023) Safety profile of subdural and depth electrode implantations in invasive EEG exploration of drug-resistant focal epilepsy. Seizure-Eur J Epilep 110:21–27. https://doi.org/10.1016/j.seizure.2023.05.022 Remick M, Akwayena E, Harford E, Chilukuri A, White GE, Abel TJ (2022) Subdural electrodes versus stereoelectroencephalography for pediatric epileptogenic zone localization: A retrospective cohort study. Neurosurg Focus 53:E4. https://doi.org/10.3171/2022.7.FOCUS2269 Schmidt RF, Wu CY, Lang MJ, Soni P, Williams KA, Boorman DW et al (2016) Complications of subdural and depth electrodes in 269 patients undergoing 317 procedures for invasive monitoring in epilepsy. Epilepsia 57:1697–1708. https://doi.org/10.1111/epi.13503 Talai A, Eschbach K, Stence NV, Palmer C, Bird W, Alexander A et al (2021) Comparison of subdural grid and stereoelectroencephalography in a cohort of pediatric patients. Epilepsy Res 177:106758. https://doi.org/10.1016/j.eplepsyres.2021.106758 Yan H, Katz JS, Anderson M, Mansouri A, Remick M, Ibrahim GM et al (2019) Method of invasive monitoring in epilepsy surgery and seizure freedom and morbidity: A systematic review. Epilepsia 60:1960–1972. https://doi.org/10.1111/epi.16315 Lee WS, Lee JK, Lee SA, Kang JK, Ko TS (2000) Complications and results of subdural grid electrode implantation in epilepsy surgery. Surg Neurol 54:346–351. https://doi.org/10.1016/s0090-3019(00)00324-4 Wong CH, Birkett J, Byth K, Dexter M, Somerville E, Gill D et al (2009) Risk factors for complications during intracranial electrode recording in presurgical evaluation of drug resistant partial epilepsy. Acta Neurochir (Wien) 151:37–50. https://doi.org/10.1007/s00701-008-0171-7 Rossmann J, Antunes ACM, Broc GG, Chan DTM, Chen SY, Dea N et al (2025) The PEG-coated collagen patch Hemopatch(r) for hemostasis and dural sealing in neurosurgery. Front Surg 12:1636372. https://doi.org/10.3389/fsurg.2025.1636372 Matsumoto H, Minami H, Yamaura I, Yoshida Y (2019) Postoperative subdural hematoma with blood flow from an epidural hematoma through a tear at the suture point of an artificial dura substitute. Acta Neurochir (Wien) 161:755–760. https://doi.org/10.1007/s00701-019-03830-7 Nagahama Y, Schmitt AJ, Nakagawa D, Vesole AS, Kamm J, Kovach CK et al (2019) Intracranial EEG for seizure focus localization: Evolving techniques, outcomes, complications, and utility of combining surface and depth electrodes. J Neurosurg 130:1180–1192. https://doi.org/10.3171/2018.1.Jns171808 Mullin JP, Shriver M, Alomar S, Najm I, Bulacio J, Chauvel P et al (2016) Is SEEG safe? A systematic review and meta-analysis of stereo-electroencephalography-related complications. Epilepsia 57:386–401. https://doi.org/10.1111/epi.13298 McGovern RA, Ruggieri P, Bulacio J, Najm I, Bingaman WE, Gonzalez-Martinez JA (2019) Risk analysis of hemorrhage in stereo-electroencephalography procedures. Epilepsia 60:571–580. https://doi.org/10.1111/epi.14668 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 17 Apr, 2026 Read the published version in Neurosurgical Review → Version 1 posted Editorial decision: Revision requested 02 Mar, 2026 Reviews received at journal 22 Feb, 2026 Reviews received at journal 21 Feb, 2026 Reviews received at journal 08 Feb, 2026 Reviewers agreed at journal 08 Feb, 2026 Reviewers agreed at journal 07 Feb, 2026 Reviewers agreed at journal 07 Feb, 2026 Reviews received at journal 06 Feb, 2026 Reviewers agreed at journal 06 Feb, 2026 Reviewers agreed at journal 05 Feb, 2026 Reviewers agreed at journal 05 Feb, 2026 Reviewers invited by journal 04 Feb, 2026 Editor assigned by journal 27 Jan, 2026 Submission checks completed at journal 14 Jan, 2026 First submitted to journal 10 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8567785","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":587781068,"identity":"47775fb6-1f41-45a8-8c9c-78789ad8003b","order_by":0,"name":"Rofat Askoro","email":"","orcid":"","institution":"Graduate School of Biomedical and Health Sciences, Hiroshima University","correspondingAuthor":false,"prefix":"","firstName":"Rofat","middleName":"","lastName":"Askoro","suffix":""},{"id":587781070,"identity":"a9f31154-54b0-4a3d-824b-9ab652725584","order_by":1,"name":"Kota Kagawa","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDUlEQVRIiWNgGAWjYBACCSBmbGBgkDNgBrMk4DLMuLUwg7UYk64lcQMD1D6CQLK9/+DHGb8Op29n53348OcOi2j+Bh4Dhh81DOzmOLRI8xxmltzYdzh3ZzO7sTHvGYncGQd4DBh7jjEwW+KwUk4imUHyYc/t3A2H2dikGdskchvuvzFg4G1gYDY4gFML80+glnQDoBbJn0At80G2/MWjRVoimU1yw4/bCSAtErxALRuAWpjx2SLZc9jMcmbDf0Ogw5iNQVo2HmArOCxzTAKnXySONz6+2fMnTd7g/DHGhz/b6nLnHWDe+PBNjU0yrhADA8Y2NAGgkySSDfBpYfiDRcwOv5ZRMApGwSgYQQAACw9Y1cWGdRcAAAAASUVORK5CYII=","orcid":"","institution":"Hiroshima University Hospital","correspondingAuthor":true,"prefix":"","firstName":"Kota","middleName":"","lastName":"Kagawa","suffix":""},{"id":587781074,"identity":"4ed7c9d5-0323-45c3-9a4d-e1b73fbbd23d","order_by":2,"name":"Go Seyama","email":"","orcid":"","institution":"Hiroshima University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Go","middleName":"","lastName":"Seyama","suffix":""},{"id":587781076,"identity":"2466c072-6a63-4531-99d5-4ce47642d4a3","order_by":3,"name":"Akitake Okamura","email":"","orcid":"","institution":"Hiroshima University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Akitake","middleName":"","lastName":"Okamura","suffix":""},{"id":587781081,"identity":"258f941d-24ae-4ddc-940c-7e4fdf8cc943","order_by":4,"name":"Yasushi Orihashi","email":"","orcid":"","institution":"Hiroshima University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yasushi","middleName":"","lastName":"Orihashi","suffix":""},{"id":587781082,"identity":"176f09f9-90f4-45fe-b8af-eff710b9af8f","order_by":5,"name":"Ayako Takamori","email":"","orcid":"","institution":"Hiroshima University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ayako","middleName":"","lastName":"Takamori","suffix":""},{"id":587781083,"identity":"95dc6224-80f9-4407-a74d-5f6ce1fa767e","order_by":6,"name":"Nobutaka Horie","email":"","orcid":"","institution":"Graduate School of Biomedical and Health Sciences, Hiroshima University","correspondingAuthor":false,"prefix":"","firstName":"Nobutaka","middleName":"","lastName":"Horie","suffix":""}],"badges":[],"createdAt":"2026-01-10 11:08:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8567785/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8567785/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10143-026-04269-y","type":"published","date":"2026-04-17T15:57:11+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":102214387,"identity":"5d02b9dc-e1f9-4091-be7c-51ca9bde3e7f","added_by":"auto","created_at":"2026-02-09 12:43:40","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":64541,"visible":true,"origin":"","legend":"\u003cp\u003eCraniotomy diameter (dashed line arrow) and craniotomy depth (solid line arrow) measurements.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8567785/v1/a13332270bde0fd7389d71c1.jpeg"},{"id":102214370,"identity":"5990555f-f214-4330-8abd-dc6266a8c5b6","added_by":"auto","created_at":"2026-02-09 12:43:36","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":128182,"visible":true,"origin":"","legend":"\u003cp\u003eAnnual frequency of dural substitute use with Gore-Tex (blue) and Seamdura (orange). Bars denote the yearly number of procedures for each material, and darker shades indicate the number of postoperative extra-axial hemorrhage in each group during the same period.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8567785/v1/a91d158ad01e9642d90cb463.jpeg"},{"id":102214362,"identity":"38d9c014-c31c-40e5-b7f8-40c0b73ee4b2","added_by":"auto","created_at":"2026-02-09 12:43:34","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":323230,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of dural closure techniques using Seamdura and Gore-Tex.\u003c/p\u003e\n\u003cp\u003e(A) Intraoperative finding revealing Seamdura used for dural closure after subdural electrode placement. (B) Corresponding schematic illustration showing that the dura edge is not in complete apposition with the Seamdura (arrow) owing to its limited flexibility.\u003c/p\u003e\n\u003cp\u003e(C) Intraoperative finding demonstrating dural closure using Gore-Tex.\u003c/p\u003e\n\u003cp\u003e(D) Corresponding schematic illustrating that the dura edge is well apposed to the Gore-Tex sheet (arrow) owing to its better pliability.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8567785/v1/9749e0d90b47eaf2486d47cb.jpeg"},{"id":107350705,"identity":"52f08739-4039-4fa3-8053-22fc08a9fed2","added_by":"auto","created_at":"2026-04-20 16:00:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1133574,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8567785/v1/5992d0af-c30b-465c-8e18-d43c640a93a0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk factors for extra-axial hemorrhage during invasive monitoring using subdural electrodes","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSurgical resection of the epileptogenic zone remains a key treatment option for focal drug-resistant epilepsy to achieve a seizure-free outcome [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The success of epilepsy surgery primarily depends on the accurate localization of the epileptogenic zone or network through presurgical evaluation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Concordant findings from seizure semiology, imaging findings, and scalp video-electroencephalography (EEG) may be sufficient to proceed with surgical resection [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, in patients with inconclusive or discordant findings, invasive intracranial EEG monitoring is commonly required to better delineate the seizure network [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTraditionally, subdural electrodes (SDEs) have been predominantly used for invasive monitoring, especially in North America, the United Kingdom, Germany, and Japan [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, with the advent of stereotactic techniques and robot-assisted surgery, stereoelectroencephalography (SEEG) has gained wider adoption [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] because of its several advantages, namely, minimal invasiveness, a lower risk of postoperative complications, easier multilobar or bilateral implantations, and the ability to record from superficial and deep brain structures [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Nevertheless, SDE implantation via craniotomy is still indicated in specific contexts by providing broad cortical coverage and enabling high-resolution functional mapping, particularly in those with perirolandic or eloquent cortex involvement [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe potential benefits of invasive monitoring with SDE implantation generally outweigh the risk of adverse events during the implantation procedure and subsequent EEG monitoring [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Hemorrhage, infections, and elevated intracranial pressure have been reported as potential complications of SDE implantation [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. A systematic review identified extra-axial hemorrhage, including subdural and epidural, as the most common complication of invasive monitoring using SDEs [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. To date, only few studies have explored the risk factors associated with extra-axial hemorrhage. Therefore, this study aimed to identify clinical and surgical variables associated with extra-axial hemorrhage during invasive monitoring using SDEs. Improved understanding of the risk factors may enhance clinical decision-making and SDE implantation safety.\u003c/p\u003e"},{"header":"Materials \u0026 Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatients\u003c/h2\u003e \u003cp\u003eWe retrospectively reviewed the medical records and operative notes of consecutive pediatric or adult patients with drug-resistant epilepsy who underwent intracranial video EEG monitoring using SDEs via craniotomy from October 2008 to September 2022 at the Department of Neurosurgery, Hiroshima University Hospital. Since 2022, a surgical robot system for SEEG has been introduced in our hospital; hence, only patients before this adaptation were included. The Ethical Committee for Clinical Research of Hiroshima University approved this study (approval number: E2025-0017).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIndication and Presurgical Evaluation\u003c/h3\u003e\n\u003cp\u003eInvasive monitoring indicated for each patient was determined based on the comprehensive presurgical evaluation. All patients had previously undergone scalp video-EEG monitoring, computed tomography (CT), magnetic resonance imaging (MRI), Wada test, neuropsychological testing, magnetoencephalography (MEG), fluorodeoxyglucose-positron emission tomography (FDG-PET), and iomazenil-single-photon emission computed tomography (IMZ-SPECT). The implantation sites and number of subdural grid and strip electrodes were carefully selected based on seizure semiology, EEG findings, and imaging results. In some patients, depth electrodes were also utilized. Besides assessing the presumed epileptogenic zone, SDEs were also implanted for mapping the eloquent cortex when needed.\u003c/p\u003e\n\u003ch3\u003eImplantation Procedure\u003c/h3\u003e\n\u003cp\u003eA platinum subdural grid electrode and strip electrodes were used for SDE implantation (Unique Medical, Tokyo, Japan). Depth electrodes were used when required. The available electrode configurations were 8\u0026times;8, 4\u0026times;8, 2\u0026times;8, or 2\u0026times;4 for grid electrodes and 1\u0026times;6 or 1\u0026times;4 for strip electrodes, with an interval of 1 cm between each electrode. Depending on the case, the unused parts of the grid electrode were trimmed to fit the brain surface coverage area. The depth electrode consisted of six contacts with a 1-cm interval. Skin incision and craniotomy size were carefully estimated to create an adequate opening for the operative field and cortical coverage area for SDE implantation. SDEs were placed directly on the exposed brain surface under visualization or slid into the brain surface under X-ray fluoroscopy. A free-hand neuronavigation-guided technique using the Curve\u0026trade; neuronavigation system was applied for depth electrode insertion (Brainlab AG, Munich, Germany). A pointer with reflective spherical markers was directly punctured into the brain and manually inserted along the planned trajectory under the neuronavigation system. After reaching the desired depth of target, the pointer was removed, and the depth electrode was manually inserted through the previous route from the pointer.\u003c/p\u003e \u003cp\u003ePost-implantation, duraplasty was performed using either an absorbable or a non-absorbable dura substitute. Dura substitutes were trimmed to fit the dural defect shape. In our study, Seamdura\u0026reg; (Gunze, Kyoto, Japan), an absorbable dura material made of poly-L-lactide copolymer and ɛ-caprolactone copolymeric film layered with polyglycolic acid (PGA), and Gore-Tex\u0026reg; (W.L. Gore \u0026amp; Associates, Flagstaff, AZ, USA), a non-absorbable dura made from expanded polytetrafluoroethylene (ePTFE), were used, which are widely available in Japan. Gore-Tex was initially used for duraplasty after SDE implantation. In 2010, Seamdura was introduced because its translucency allowed direct visualization of any positional shift of the SDE after duraplasty. The dura substitute was sutured to the native dura using a synthetic, non-absorbable braided suture (Nurolon\u0026reg;, Johnson \u0026amp; Johnson, Somerville, NJ, USA). Electrode leads were routed subcutaneously and sutured to the skin using a nylon suture to prevent positional shift. The autologous bone flap was fixed back, and adequate dural tenting was performed. Dural, galeal, muscular, and skin bleeding were sufficiently coagulated by applying bipolar electrocautery.\u003c/p\u003e \u003cp\u003eBetween October 2008 and September 2022, each surgery was performed by a team of two or three operators drawn from four attending neurosurgeons: Takeshi Nishimoto (worked from October 2008 to March 2012), K.K (worked from October 2008 to March 2016 and from July 2017 to September 2022), Masaya Katagiri (worked from April 2011 to August 2017 and from April 2019 to September 2022), and G.S. (worked from April 2016 to September 2022). All four operators were well-trained neurosurgeons with 7\u0026ndash;11 years of experience at the time of their arrival.\u003c/p\u003e\n\u003ch3\u003ePostoperative Protocol\u003c/h3\u003e\n\u003cp\u003eAll patients underwent an immediate postoperative head CT scan following SDE implantation and a routine repeat scan on postoperative day 1. Intracranial video EEG monitoring was started on day 1 and continued until the number of captured ictal recordings was sufficient under a tapered antiseizure medication. Additional CT scans were performed if any clinical signs suggestive of complications were observed during the monitoring period. Post-monitoring, a head CT scan was routinely performed. Electrical stimulation was performed to map out the eloquent area when required. Prophylactic antibiotics were administered intravenously or orally throughout the SDE implantation period. The subsequent surgery for electrode removal was prescheduled based on the duration required for scalp video-EEG monitoring. Cortical resection was performed at the time of electrode removal as indicated.\u003c/p\u003e\n\u003ch3\u003eDefinition of Complication\u003c/h3\u003e\n\u003cp\u003eComplications were defined as follows: (1) any neurological deficit occurring from electrode placement to removal; (2) any clinical events requiring surgical intervention; (3) infections occurring during the monitoring period until electrode removal; (4) abnormalities detected on head CT scan, including postoperative intracerebral, subdural and epidural hemorrhage. For extra-axial hemorrhage, a high-density lesion on axial CT scan with a thickness of \u0026ge;\u0026thinsp;1 cm was considered a complication, regardless of the presence or absence of any symptoms. Infections occurring after electrode removal or resective surgery were not included. The cause of each complication was thoroughly investigated, including the presence of any technical problems. For extra-axial hemorrhage, statistical analysis was performed to identify possible risk factors.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eData Collection\u003c/h2\u003e \u003cp\u003eThe following data were collected as potential risk factors for the occurrence of extra-axial hemorrhage: age at surgery, sex, seizure duration, seizure type, the presence of MRI lesions, the number of antiseizure medications (ASMs), hemoglobin (Hb), platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), laterality of electrode placement (unilateral vs bilateral placement), maximum grid size (33\u0026ndash;64 electrodes vs 8\u0026ndash;32 electrodes), total number of electrodes, total number of leads, use of depth electrodes, maximum craniotomy diameter and depth, selection of an artificial dura substitute (Gore-Tex vs Seamdura), and surgical duration. The craniotomy diameter and depth were retrospectively measured on an axial or coronal image of the postoperative CT scan (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Seizure outcome was evaluated at 2 years postoperatively using the Engel classification [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStatistical Analysis for Extra-axial Hemorrhage\u003c/h3\u003e\n\u003cp\u003eStatistical analysis was performed using JMP 18 (SAS Institute Inc.). The incidence of extra-axial hemorrhage, regardless of symptoms, was considered as the outcome of interest (dependent variable). Independent variables included in the model were as follows: age at surgery, sex, seizure duration, seizure type, presence of MRI lesions, number of ASMs, Hb, platelet count, PT, APTT, laterality of electrode placement (unilateral vs bilateral hemisphere), maximum grid size (33\u0026ndash;64 electrodes vs 8\u0026ndash;32 electrodes), total number of electrodes, total number of leads, use of depth electrodes, maximum craniotomy diameter and depth, selection of an artificial dura substitute, and surgical duration. Univariate analyses were performed using Pearson\u0026rsquo;s chi-square test for categorical variables and the Mann-Whitney U-test for continuous variables. Variables with p\u0026thinsp;\u0026lt;\u0026thinsp;0.5 in the univariate analysis were included in the multivariate logistic regression analysis to determine risk factors for extra-axial hemorrhage. The least absolute shrinkage and selection operator (LASSO) regression was applied to stabilize model estimation in the multivariate analysis. Odds ratios with 95% confidence intervals (CI) and p-values were calculated, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003ePatient Characteristics\u003c/h2\u003e\n \u003cp\u003eA total of 64 patients were included in this study. Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e presents the summary of patient demographics and clinical characteristics, including postoperative complications. The median age at the time of surgery was 29 (range: 1\u0026ndash;63) years, and the median duration of epilepsy was 16 (range: 1\u0026ndash;49) years. MRI findings detected no lesion in 38 patients (59.3%). Focal-impaired awareness seizure (FIAS) and focal to bilateral tonic\u0026ndash;clonic seizure (FBTCS) were observed in 30 (46.8%) and 9 (14.1%) patients, respectively, and a combination of FIAS and FBTCS was observed in 13 (20.3%) patients. Focal-onset motor seizures occurred in nine (14.1%) patients. Sixteen patients (25.0%) had complications related to SDE implantation, with the most common being the presence of extra-axial hemorrhage, including subdural and epidural. No incidence of intracerebral hemorrhage was observed. Of the 16 patients, surgical intervention was required in five patients (7.8%). No permanent neurological deficits were observed in all patients with complications. Resective surgery was required in 60 (93.8%) patients after an invasive monitoring period. An Engel class I outcome was achieved in 36 patients at 2 years postoperatively. Engel class II and III outcomes were achieved in 10 and 9 patients, respectively. Five patients remained in the Engel class IV category.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDemographic data and clinical characteristics\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCharacteristics\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eValue\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge (median, range)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29 (1\u0026ndash;63)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSex distribution (male : female)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37 : 27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeizure duration (years) (median, range)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16 (1\u0026ndash;49)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMRI lesion\u003c/p\u003e\n \u003cp\u003eDetected\u003c/p\u003e\n \u003cp\u003eUndetected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNumber of antiseizure medications (median, range)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3 (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeizure type:\u003c/p\u003e\n \u003cp\u003eFIAS\u003c/p\u003e\n \u003cp\u003eFBTCS\u003c/p\u003e\n \u003cp\u003eFIAS\u0026thinsp;+\u0026thinsp;FBTCS\u003c/p\u003e\n \u003cp\u003eFMS\u003c/p\u003e\n \u003cp\u003eOther\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePostoperative complications *\u003c/p\u003e\n \u003cp\u003eExtra-axial hemorrhage\u003c/p\u003e\n \u003cp\u003eIntracerebral hemorrhage\u003c/p\u003e\n \u003cp\u003eInfection\u003c/p\u003e\n \u003cp\u003eIncreased intracranial pressure due to tight duraplasty\u003c/p\u003e\n \u003cp\u003eBrain edema due to venous compression\u003c/p\u003e\n \u003cp\u003eElectrode malfunction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e13 (2)\u003c/p\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeizure outcome (Engel Classification)\u003c/p\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003cp\u003eII\u003c/p\u003e\n \u003cp\u003eIII\u003c/p\u003e\n \u003cp\u003eIV\u003c/p\u003e\n \u003cp\u003eNo further resective surgery\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\"\u003eFIAS\u0026thinsp;=\u0026thinsp;focal impaired aware seizure; FBTCS\u0026thinsp;=\u0026thinsp;focal to bilateral tonic-clonic seizure; FMS: focal onset motor seizure. *The number of patients who required surgical intervention is given in parentheses.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eSurgical Factors\u003c/h2\u003e\n \u003cp\u003eSDEs were implanted in the unilateral and bilateral hemispheres in 41 and 23 patients, respectively. Thirty patients had a subdural grid with a size of \u0026ge;\u0026thinsp;33 contacts. The median number of total electrodes was 98 (range: 32\u0026ndash;136). Depth electrodes were used in 52 patients, in which the number of leads of depth electrodes ranged from 1 to 4. The median craniotomy diameter was 113.77 (range: 78.64\u0026ndash;142.31) mm. The selection of artificial dura substitutes is shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. Seamdura was first introduced in 2010 and used more frequently than Gore-Tex between 2011 and 2015. In all other years, Gore-Tex remained the predominant material used.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eCharacteristics of Patients with Extra-axial Hemorrhage\u003c/h2\u003e\n \u003cp\u003eThirteen patients (20.3%) experienced extra-axial hemorrhage, the most common complication after SDE implantation. The patient characteristics are summarized in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. Of the 13 patients, two underwent emergency surgical intervention for hematoma removal due to considerable neurological symptoms. One patient (patient no.7 in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) experienced severe nausea, vomiting, and headache, and these symptoms worsened. A CT scan on postoperative day 1 revealed signs of brain parenchymal compression due to an extra-axial hematoma, requiring emergency hematoma removal. During hematoma removal, persistent bleeding was evident from the edge of the dural incision. The other patient (patient no. 9 in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) developed a gradually worsening headache and confusion during the video-EEG monitoring. CT scan on postoperative day 7 revealed a thick extra-axial hematoma and brain compression, needing emergency hematoma removal. Both patients fully recovered from the symptoms after hematoma removal. In the remaining 11 patients who did not develop notable symptoms, their postoperative course was managed with close monitoring. In 13 patients with extra-axial hemorrhage, the hematoma location was above the subdural electrodes in 12 patients. Seamdura was used in nine patients, whereas Gore-Tex was used in four patients. The thickness of the hematoma increased over time in 7 of 11 patients who did not undergo surgical intervention. No patient with extra-axial hemorrhage developed cerebral contusion or vascular injury, which was confirmed upon subdural electrode removal.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCharacteristics of patients with extra-axial hemorrhage complication.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCase no.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAge (yrs) / Sex\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDuration of implantation (days)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eHemorrhage thickness changes from day 1 \u0026rarr; latest (cm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eHematoma location (relative to electrode)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eHematoma type\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaxiumum craniotomy diameter (mm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDura substitute at implantation\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSurgical intervention\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eInterval from implantation to evacuation surgery (days)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSubsequent resection site\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSeizure Outcome (Engel Class)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnder\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e135\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGore-Tex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e52/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e128.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGore-Tex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e39/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e123.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. F T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eII\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e46/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e115.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e85.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. F T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIV\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.8 (removed)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e114.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHematoma removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e133.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 2.5 (removed)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e138.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHematoma removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIV\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63/F\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e106.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. T\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eII\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e53/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.4 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e130.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGore-Tex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLt. C P\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e47/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e107.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. hemisphere\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19/M\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;1 \u003cstrong\u003e\u0026rarr;\u003c/strong\u003e 1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbove\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSDH, EDH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e125.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGore-Tex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRt. P\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eI\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"12\"\u003eSDH\u0026thinsp;=\u0026thinsp;subdural hematoma; EDH\u0026thinsp;=\u0026thinsp;epidural hematoma; Lt. = left; Rt. = right; F\u0026thinsp;=\u0026thinsp;frontal; T\u0026thinsp;=\u0026thinsp;temporal; P\u0026thinsp;=\u0026thinsp;parietal; C\u0026thinsp;=\u0026thinsp;central. Engel class indicates seizure outcome at 12-month follow-up. \u0026ldquo;\u0026mdash;\u0026rdquo; indicates no surgical intervention was required.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003eOther Complications\u003c/h2\u003e\n \u003cp\u003eOther complications are listed in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. Intracranial pressure increased in one patient owing to tight duraplasty, which resolved after decompression. One patient underwent emergency surgical intervention on postoperative day 1 due to left hemiparesis. The CT scan revealed cerebral edema in the right hemisphere. Intraoperatively, electrode leads were found to be compressing a cortical vein near the primary motor cortex. The leads were replaced with smaller electrodes and repositioned, resulting in clinical condition improvement. Another patient experienced electrode damage from a hyperkinetic seizure, requiring emergency replacement of the electrode. All patients who required surgical intervention for complications recovered without permanent neurological deficits.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003eUnivariate and Multivariate Analysis for Extra-axial Hemorrhage\u003c/h2\u003e\n \u003cp\u003eUnivariate analysis revealed that postoperative extra-axial hemorrhage was significantly associated with a higher number of electrodes (p\u0026thinsp;=\u0026thinsp;0.013), higher number of leads (p\u0026thinsp;=\u0026thinsp;0.032), and use of Seamdura (p\u0026thinsp;=\u0026thinsp;0.008; Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). No patient-specific variables were significantly associated with the extra-axial hemorrhage.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eUnivariate analysis for the risk of extra-axial hemorrhage during invasive recording.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eControl group\u003c/p\u003e\n \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;51)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eExtra-axial hemorrhage (n\u0026thinsp;=\u0026thinsp;13)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eP value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePatient-specific factor\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge at surgery, years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28 (1\u0026ndash;59)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e39 (14\u0026ndash;63)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0518\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSex:\u003c/p\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.7627\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresence of MRI lesion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2102\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNo. of ASMs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3 (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3 (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8086\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHemoglobin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.2 (4.3\u0026ndash;16.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.2 (11.5\u0026ndash;16.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8216\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePlatelet count\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e240 (108\u0026ndash;457)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e209 (152\u0026ndash;383)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2893\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePT time\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.7 (10\u0026ndash;13.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.5 (10\u0026ndash;12.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.0000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAPTT\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29.95 (21.4\u0026ndash;35.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.8 (25\u0026ndash;39.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8368\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSurgery-specific factor\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLaterality of electrode placement:\u003c/p\u003e\n \u003cp\u003eUnilateral\u003c/p\u003e\n \u003cp\u003eBilateral\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0505\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaximum grid size:\u003c/p\u003e\n \u003cp\u003e8\u0026ndash;32\u003c/p\u003e\n \u003cp\u003e33\u0026ndash;64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.0000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNumber of electrodes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e96 (32\u0026ndash;136)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e110 (96\u0026ndash;132)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0138*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNumber of leads\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11 (4\u0026ndash;18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13 (10\u0026ndash;17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0320*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUse of depth electrodes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2431\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaximum craniotomy diameter (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e111.35 (78.64\u0026ndash;142.31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e123.44 (85.94\u0026ndash;138.97)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0735\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaxiumum craniotomy depth (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.79 (6.41\u0026ndash;31.24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.7 (7.1\u0026ndash;33.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.4903\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArtificial dura material:\u003c/p\u003e\n \u003cp\u003eGore-Tex\u003c/p\u003e\n \u003cp\u003eSeamdura\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0087*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSurgical duration (minutes)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e422 (279\u0026ndash;720)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e442 (356\u0026ndash;648)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5991\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eASM\u0026thinsp;=\u0026thinsp;antiseizure medications, PT\u0026thinsp;=\u0026thinsp;prothrombin time, APTT\u0026thinsp;=\u0026thinsp;activated partial thromboplastin time\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eFour variables were selected using the LASSO approach in the multivariate analysis (Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). The analysis identified the use of Seamdura as an artificial dura substitute as independent risk factor of extra-axial hemorrhage than the use of Gore-Tex (OR\u0026thinsp;=\u0026thinsp;7.69, 95% CI: 2.39\u0026ndash;24.72, p\u0026thinsp;=\u0026thinsp;0.0006). The remaining variables including age at surgery, number of electrodes, and maximum craniotomy diameter did not significantly demonstrate the predictive risk for extra-axial hemorrhage.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab4\" border=\"1\" class=\"fr-table-selection-hover\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMultivariate analysis for the risk of extra-axial hemorrhage during invasive monitoring.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eOR\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e95% CI\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eP value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge at surgery, years\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.97\u0026ndash;1.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3404\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNumber of electrodes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.99\u0026ndash;1.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaximum craniotomy diameter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.98\u0026ndash;1.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1651\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArtificial dura material (Seamdura)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.39\u0026ndash;24.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0006*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eSummary of Results\u003c/h2\u003e \u003cp\u003eThis retrospective study analyzed the complications following SDE implantation for intracranial video-EEG monitoring and identified the risk factors associated with extra-axial hemorrhage in 64 patients with drug-resistant epilepsy. Thirteen (20.3%) patients developed extra-axial hemorrhage on CT scan after SDE implantation. Multivariate analysis identified the use of Seamdura as the artificial dura substitute as the independent predictive factors for extra-axial hemorrhage. Other complications in our series consisted of elevated intracranial pressure due to tight duraplasty, brain edema secondary to venous compression by the implanted electrode lead, and electrode malfunction due to hyperkinetic seizures. Common complications, such as intracerebral hemorrhage and infections, reported in previous studies were not observed in our cohort. Although unplanned emergency surgical intervention was performed for two patients with extra-axial hemorrhage and three with other complications, no patients experienced permanent neurological deficits or death.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eHemorrhagic Complications Following SDE Implantation\u003c/h2\u003e \u003cp\u003ePrevious studies have documented symptomatic hemorrhagic complications following SDE implantation in pediatric and adult patients, with reported rates between 1.4% and 11% [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR17 CR18 CR19 CR20 CR21\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, hemorrhagic complication rates increase to 16\u0026ndash;38% when considering imaging-only hemorrhages [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Extra-axial hemorrhage, including subdural and epidural, has been reported as the most common form of hemorrhagic complications [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. A previous systematic review reported that among 2036 patients, the incidences of extra-axial hemorrhage and intracerebral hemorrhage were 3.4% and 1.4%, respectively [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Subdural hemorrhage is reported as the most predominant among extra-axial hemorrhages [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Thirteen patients (20.3%) in our cohort had extra-axial hemorrhage on CT scan, which is comparable with those of previous reports.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eRisk Factors for Extra-axial Hemorrhage\u003c/h2\u003e \u003cp\u003eThe cause of extra-axial hematoma formation without intraoperative bleeding is still not fully understood [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Lee et al. reported that delayed subdural hematoma formation is one of the major complications, in which the hematoma showing progressive enlargement within 3 days after SDE insertion [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Previous studies have indicated that the number of electrode contacts or the size of grids influences the likelihood of hemorrhagic complications [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Specifically, 67 or more electrode contacts [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] and the use of grids with 64 contacts [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] have been reported as risk factors.\u003c/p\u003e \u003cp\u003eIn our case series, the use of an absorbable dura (Seamdura) have been identified as independent risk factors for extra-axial hemorrhage. Hematomas were more frequently located outside the SDE rather than beneath it. In some cases, the size of the hematoma gradually increased over a week. No findings of cerebral contusion or vascular damage were observed in any patient with extra-axial hemorrhage. These observations indicate that bleeding from the edge of the dural incision plays a major role in extra-axial hematoma formation. Despite achieving adequate dural hemostasis using standard bipolar coagulation during surgery, postoperative rebleeding may occur [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Because the dural suture line lies between SDE and the bone flap, no living tissue comes into contact with the suture site, which could create an environment that could hinder wound healing at the edge of the dural incision.\u003c/p\u003e \u003cp\u003eThe use of Seamdura (absorbable dural substitutes) was notably associated with extra-axial hemorrhage in our study, a finding not previously discussed in the literature. Several differences exist between Gore-Tex (non-absorbable dural substitute) and Seamdura (absorbable substitute), as summarized in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e: (1) Regarding transparency, Gore-Tex is opaque, whereas Seamdura is translucent and can be easily trimmed to fit the shape of the dural defect. SDE can be observed through Seamdura even after dural closure. (2) Seamdura is a weaker material than Gore-Tex. Matsumoto et al. reported that Seamdura has lesser suture point strength compared to Gore-Tex, which further decreases after 48-hour incubation [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. (3) Gore-Tex has higher pliability than Seamdura. When a surgeon grasps any part of the artificial dura with tweezers, Gore-Tex can be easily pleated, whereas Seamdura can flatten and not be pleated as easily. Among these differences, we considered material strength and pliability to have the greatest influence on extra-axial hemorrhage formation (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). While a stronger material of Gore-Tex allows application of a tight suture between the artificial dura and the edge of the dural incision, a weaker material of Seamdura may cause artificial dural tearing. The easy-pleating property of Gore-Tex allows it to adhere closely to the edge of the dural incision, thereby minimizing bleeding from the incision edges. Our results indicate the influence of selecting the artificial dura substitute on the risk of developing extra-axial hemorrhage. Gore-Tex is preferred over Seamdura for duraplasty during SDE implantation to prevent extra-axial hemorrhage.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of dura substitute\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGore-Tex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSeamdura\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterials\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExpanded polytetrafluoroethylene (ePTFE)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePoly-L-lactide copolymer and ɛ-caprolactone copolymeric film layered with polyglycolic acid (PGA)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOpacity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOpaque\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTranslucent\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePliability\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMore pliable and flexible\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess pliable compliant\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial strength\u003csup\u003e27\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHigher\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLower\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eOther Complications and the Future of SDE Implantation\u003c/h2\u003e \u003cp\u003eAs complications other than extra-axial hemorrhage, elevated intracranial pressure owing to tight duraplasty and brain edema secondary to venous compression by the implanted electrode lead were observed. Both complications were attributed to technical factors. We did not recognize these issues during electrode implantation; however, the cause of the former was noted through postoperative CT and the latter during reoperation. This feedback was applied in subsequent surgeries, and the same mistakes were not repeated. Previous studies also indicated that increasing procedural experience can reduce SDE-related complications over time [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOne patient underwent surgical intervention for electrode malfunction caused by hyperkinetic seizures. Such complications can occur with invasive monitoring using SDE and SEEG in patients with focal hyperkinetic seizures or generalized seizures. Appropriate case selection and careful monitoring are necessary. We had no cases of infection, which may be attributed to the continued administration of antibiotics while SDEs were in place. Infections occurring after electrode removal and focal cortical resection were not included in this study.\u003c/p\u003e \u003cp\u003eIn summary, all SDE-related complications in our series occurred in the extra-axial space, which contrasts with complications from depth electrode insertion for SEEG. SEEG-related hemorrhages are predominantly intra-axial cerebral hemorrhages [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] and intracerebral hemorrhage that may cause permanent neurological deficits [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In contrast, for problems occurring outside the brain, prompt and timely surgical intervention can prevent permanent neurological deficit. Although surgical intervention was required in five patients in our series, no permanent neurological deficits or deaths were reported. Although SDE implantation is clearly more invasive than SEEG, with high operator skill and careful observation during SDE implantation, it may decrease the permanent complication rate compared to SEEG. As the field moves toward a paradigm shift from SDE to SEEG, maintaining the skills of SDE implantation is an important issue.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eLimitation\u003c/h2\u003e \u003cp\u003eThe current study has several limitations. The retrospective, single-center design and the small sample size limit the associations identified in the results. Although the surgical procedure and postoperative protocol remained unchanged during the study period, potential factors may have been influenced by the passage of time. For example, the learning curve for surgeons\u0026rsquo; skills is difficult to assess. Our preference for the selection of an artificial dura substitute changed over time. The artificial dura substitutes examined (Seamdura and Gore-Tex) are commonly used in Japan, and their availability may differ in other regions, further limiting external applicability. Different absorbable artificial dura products may exhibit different properties. Future multicenter prospective studies with standardized imaging protocols and broader material comparisons are needed to validate and generalize our findings.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eSelection of an artificial dura substitute in duraplasty contributes to extra-axial hemorrhage after SDE implantation. The use of an absorbable dura was associated with a higher risk of extra-axial hemorrhage. The use of non-absorbable dura substitutes with high pliability and superior mechanical stability is recommended to prevent extra-axial hemorrhage after SDE implantation. Because extra-axial hematoma may grow over time, careful observation is essential during SDG implantation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure of Conflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no relevant financial or non-financial interest regarding the production of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRofat Askoro:\u0026nbsp;\u003c/strong\u003estudy design; data curation; data analysis; interpretation of results; writing original draft; visualization. \u003cstrong\u003eKota Kagawa:\u0026nbsp;\u003c/strong\u003ewriting and review final draft; validation; supervision; data analysis; conceptualization; project administration. \u003cstrong\u003eGo Seyama\u003c/strong\u003e: methodology; validation; data curation; writing\u0026mdash;review \u0026amp; editing; investigation. \u003cstrong\u003eAkitake Okamura\u003c/strong\u003e: writing\u0026mdash;review \u0026amp; editing; validation; investigation; data curation. \u003cstrong\u003eYasushi Orihashi\u003c/strong\u003e: writing\u0026mdash;review \u0026amp; editing, validation, data analysis; methodology; interpretation of results. \u003cstrong\u003eAyako Takamori\u003c/strong\u003e: writing\u0026mdash;review \u0026amp; editing, validation, data analysis; methodology; interpretation of results. \u003cstrong\u003eNobutaka Horie\u003c/strong\u003e: writing\u0026mdash;review \u0026amp; editing; validation; supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by The Ethical Committee for Clinical Research of Hiroshima University (approval number: E2025-0017). We confirm that we have read the Journal\u0026rsquo;s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient Consent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study implemented an opt-out arrangement by providing necessary information for informed decision and adequate measures to anonymize medical information and images in accordance with Hiroshima University Hospital policy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJobst BC, Cascino GD (2015) Resective epilepsy surgery for drug-resistant focal epilepsy a review. 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Epilepsia 57:386\u0026ndash;401. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/epi.13298\u003c/span\u003e\u003cspan address=\"10.1111/epi.13298\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcGovern RA, Ruggieri P, Bulacio J, Najm I, Bingaman WE, Gonzalez-Martinez JA (2019) Risk analysis of hemorrhage in stereo-electroencephalography procedures. Epilepsia 60:571\u0026ndash;580. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/epi.14668\u003c/span\u003e\u003cspan address=\"10.1111/epi.14668\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"neurosurgical-review","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nrev","sideBox":"Learn more about [Neurosurgical Review](https://www.springer.com/journal/10143)","snPcode":"10143","submissionUrl":"https://submission.nature.com/new-submission/10143/3","title":"Neurosurgical Review","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"subdural electrodes, extra-axial hemorrhage, adverse events, epilepsy surgery, dura substitute","lastPublishedDoi":"10.21203/rs.3.rs-8567785/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8567785/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDespite the increasing use of stereoelectroencephalography, subdural electrode (SDE) implantation remains valuable to identify the epileptogenic network. Extra-axial hemorrhage, including subdural and epidural, is one of the most frequent complications of SDE implantation. This study aimed to identify risk factors associated with extra-axial hemorrhage post–SDE implantation in patients with focal drug-resistant epilepsy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe retrospectively reviewed consecutive patients who underwent SDE implantation via craniotomy at Hiroshima University Hospital between 2008 and 2022. Multivariate logistic regression analysis was performed to identify risk factors for postoperative extra-axial hemorrhage.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 64 patients were included in the analysis; 13 of them had extra-axial hemorrhage after SDE implantation, and two required hematoma evacuation. The hematoma thickness increased over time in 7 of 11 patients who did not undergo surgical intervention. Univariate analysis revealed that extra-axial hemorrhage was associated with the number of electrodes (p = 0.0138), the number of leads (p = 0.0320) and selection of an artificial dura substitute (p = 0.0087). In multivariate analysis, the use of an absorbable artificial dura substitute for duraplasty (OR = 7.69, 95% CI: 2.39–24.72, p = 0.0006) was independent risk factors for post-implantation extra-axial hemorrhage.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe use of an absorbable artificial dura substitute for duraplasty is associated with the occurrence of extra-axial hemorrhage after SDE implantation. The risk of this complication can be minimized through careful selection of dura substitute materials. Close observation is essential during SDE implantation because an extra-axial hematoma may develop over time.\u003c/p\u003e","manuscriptTitle":"Risk factors for extra-axial hemorrhage during invasive monitoring using subdural electrodes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-09 12:40:40","doi":"10.21203/rs.3.rs-8567785/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-02T17:19:00+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-22T08:21:53+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-21T21:27:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-08T17:44:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"133291842345053293066701282789309367996","date":"2026-02-08T13:56:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"327862985960048002233606484389424304036","date":"2026-02-08T00:29:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"110682225273574017127612341906867220786","date":"2026-02-07T05:28:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-06T08:29:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"235496496008337163009093282023625070913","date":"2026-02-06T07:03:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"124225110739139102300709811957703807226","date":"2026-02-05T11:57:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"111871196060420802385281666362206324119","date":"2026-02-05T08:38:39+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-05T04:56:02+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-27T22:35:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-14T20:42:29+00:00","index":"","fulltext":""},{"type":"submitted","content":"Neurosurgical Review","date":"2026-01-10T10:49:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"neurosurgical-review","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nrev","sideBox":"Learn more about [Neurosurgical Review](https://www.springer.com/journal/10143)","snPcode":"10143","submissionUrl":"https://submission.nature.com/new-submission/10143/3","title":"Neurosurgical Review","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2673dfaa-3f8c-4231-8f76-f92a99ceff2c","owner":[],"postedDate":"February 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-20T16:00:17+00:00","versionOfRecord":{"articleIdentity":"rs-8567785","link":"https://doi.org/10.1007/s10143-026-04269-y","journal":{"identity":"neurosurgical-review","isVorOnly":false,"title":"Neurosurgical Review"},"publishedOn":"2026-04-17 15:57:11","publishedOnDateReadable":"April 17th, 2026"},"versionCreatedAt":"2026-02-09 12:40:40","video":"","vorDoi":"10.1007/s10143-026-04269-y","vorDoiUrl":"https://doi.org/10.1007/s10143-026-04269-y","workflowStages":[]},"version":"v1","identity":"rs-8567785","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8567785","identity":"rs-8567785","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}