Independent Predictors of Surgical View Obstruction in Microvascular Decompression for Trigeminal Neuralgia: A Multifactorial Analysis

Independent Predictors of Surgical View Obstruction in Microvascular Decompression for Trigeminal Neuralgia: A Multifactorial Analysis | 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 Independent Predictors of Surgical View Obstruction in Microvascular Decompression for Trigeminal Neuralgia: A Multifactorial Analysis Methee Wongsirisuwan, Thitikan Wangapakul, Sujin Rujimethapass This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7465273/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction: Microvascular decompression (MVD) is an effective surgical treatment for trigeminal neuralgia (TGN), but intraoperative anatomical variations may obstruct the surgical view and complicate exposure of the neurovascular conflict (NVC). While suprameatal tubercle (SMT) enlargement is a known cause of surgical view obstruction (SVO), other contributory factors remain underexplored. This study investigates the additional anatomical and technical factors associated with SVO during MVD and examines whether SVO affects postoperative pain outcomes. Methods A retrospective review was conducted on 95 patients who underwent MVD for TGN between January 2015 and June 2024. Demographic data, radiographic findings, intraoperative variables, and pain scores were analyzed. Univariate and multivariate statistical analyses were performed to identify factors associated with SVO and postoperative pain relief. Results SVO was observed in 15 patients (15.79%). Multivariate logistic regression identified three independent predictors of SVO: SMT enlargement (p < 0.001), presence of a dolichoectatic vertebrobasilar artery (p = 0.040), and sitting surgical position (p = 0.019). Although SVO was associated with a significantly longer operative time (p = 0.024), it did not adversely affect short-term pain relief (p = 0.901). Conclusion SVO during MVD for TGN is multifactorial and not limited to SMT enlargement. Dolichoectatic vascular anatomy and the sitting surgical position also contribute significantly to SVO. Thorough preoperative imaging and individualized intraoperative strategies are essential for optimizing visualization and improving surgical efficiency. trigeminal neuralgia microvascular decompression suprameatal tubercle surgical view obstruction dolichoectasia retrosigmoid approach Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Microvascular decompression (MVD) is a well-established surgical intervention for trigeminal neuralgia (TGN), particularly effective in cases with radiologically confirmed neurovascular compression (NVC). The retrosigmoid approach provides direct access to the dorsal root entry zone (DREZ), where NVC most commonly occurs. Despite its effectiveness, MVD can be technically challenging due to anatomical variations that obstruct the surgical corridor, impeding visualization and the manipulation of neurovascular structures. One of the most frequently cited anatomical impediments is the suprameatal tubercle (SMT)—a bony prominence of variable size located at the posterior aspect of the petrous part of the temporal bone. In patients with a markedly enlarged SMT, visualization of the trigeminal nerve may be restricted (Fig. 1 ), occasionally necessitating partial removal of the SMT to improve surgical exposure. Previous studies have highlighted the significance of SMT dimensions and proposed morphometric thresholds, such as a height ≥ 4.8 mm, to predict the need for SMT removal. However, SVO is not always attributable to SMT hypertrophy. Additional anatomical or positional factors may contribute to impaired visualization during MVD. Methods and Materials Study Design and Patient Selection Inclusion criteria: Adult patients diagnosed with classical TGN according to the International Headache Society (IHS) criteria [ 1 ]. Undergoing MVD via the retrosigmoid approach between January 2015–June 2024. Exclusion criteria: Previous posterior fossa surgery on the same side. TGN secondary to intracranial tumors or other non-vascular compressive lesions. History of Gamma Knife radiosurgery. Use of alternative surgical approaches (e.g., subtemporal or anterior petrosal). Definition of Surgical View Obstruction (SVO) SVO is defined as intraoperative difficulty in adequately visualizing the trigeminal nerve from DREZ to the entrance of Meckel’s cave during MVD, despite standard exposure techniques. The determination of SVO was based on the combination of intraoperative findings and preoperative imaging and categorized according to defined anatomical and technical criteria. SVO was considered present when any of the following conditions were met: 1. Bony obstruction: Prominent suprameatal tubercle (SMT) with a height ≥ 4.8 mm on preoperative CT imaging, consistent with the criteria proposed by Iwasaki et al. [ 2 ]. SMT protruding into the surgical corridor and requiring bone drilling for adequate exposure. 2. Vascular obstruction: Presence of a dolichoectatic vertebrobasilar artery (VA) or other tortuous/bulky vessels that displaced or obscured the trigeminal nerve. Offending vessel requiring complex retraction or manipulation to access the NVC. 3. Cistern crowding or technical limitations: Narrow cerebellopontine angle (CPA) cistern (subjectively tight operative field despite CSF release). Intraoperative inability to achieve an adequate surgical corridor through standard techniques (e.g., table tilt, microscope angulation, cerebellar retraction) necessitating additional adjustments or SMT removal. For improved granularity, SVO was further classified into three grades based on intraoperative impact (Table 1 ): Table 1 Proposed classification of SVO Grade Definition Grade I (Mild) Slight visual limitation resolved by standard adjustments (e.g., CSF drainage, microscope angle); no SMT removal needed. Grade II (Moderate) Obstructed view requiring additional maneuvers such as table repositioning, cerebellar retraction, or angled endoscopy; SMT removal not required. Grade III (Severe) Significant obstruction requiring SMT drilling and/or advanced dissection due to bony prominence or dolichoectatic vasculature. Only patients meeting the criteria for Grades II or III were classified as having significant SVO for statistical analysis. The decision flowchart summarizing intraoperative criteria for SMT removal is shown in Fig. 2 . Data Collection Demographic, clinical, radiological, and intraoperative variables were extracted, including: Age, gender, body weight, and side of the lesion Presence of SMT enlargement on imaging Intraoperative position (supine vs. sitting) Type of vascular offender Operation time Presence of SVO Pre and postoperative numeric rating scale (NRS) for pain Postoperative pain outcomes were assessed at the first outpatient visit within one month after surgery. Ethical Considerations The study protocol was approved by the Rajavithi Institutional Review Board (IRB 106/2567). Informed consent was waived due to the retrospective nature of the study and use of anonymized data. All data were handled in accordance with ethical and privacy standards. Statistical Analysis Data were analyzed using GraphPad Prism 8 (GraphPad Software Inc.). Continuous variables were presented as mean ± standard deviation, and categorical variables as counts and percentages. The normality of distribution was assessed using the Shapiro-Wilk test. Univariate analysis was performed using Student’s t-test or Mann–Whitney U test for continuous variables and chi-square or Fisher’s exact test for categorical variables. Multivariate analysis using binary logistic regression was conducted to identify independent predictors of SVO. Variables with a p ≤ 0.05 in univariate analysis were included in the regression model. Results Patient Characteristics A total of 95 patients with classical TGN underwent microvascular decompression (MVD) via the retrosigmoid approach. The mean age was 55.8 ± 12.7 years, and 56.8% were female. Most procedures were performed in the supine position (74.74%), with the remaining in the sitting position (25.26%). Nine patients (9.47%) had SMT enlargement (≥ 4.8 mm). The superior cerebellar artery (SCA) was the most common offending vessel (71.58%), followed by veins (15.79%) and the presence of a dolichoectatic vertebrobasilar artery (9.47%). The mean preoperative NRS score was 8.97 ± 0.64, which improved significantly to 0.25 ± 0.83 postoperatively. Demographic and operative data are summarized in Table 2 . Table 2 Patient demographics and intraoperative characteristics Variable Value Total Patients 95 Mean Age (years) 55.8 ± 12.7 Female (%) 56.8% Supine Position (%) 74.74% Sitting Position (%) 25.26% SMT Enlargement (≥ 4.8 mm) 9 (9.47%) Dolichoectatic Vertebrobasilar Artery 9 (9.47%) SCA as Offending Vessel (%) 71.58% Mean Pre-op NRS 8.97 ± 0.64 Mean Post-op NRS 0.25 ± 0.83 Incidence and Predictors of Surgical View Obstruction (SVO) SVO was documented in 15 patients (15.79%). The positive factors related to SVO were sitting position (p = 0.004), SMT enlargement (p < 0.001), and the presence of a dolichoectatic vertebrobasilar artery (p = 0.048). Operation time was significantly longer in patients with SVO (p = 0.024). Other factors, including age, gender, side of involvement, and body weight, were not significantly associated with SVO (p > 0.05). There was no significant difference in the degree of pain reduction (ΔNRS score) between the SVO and non-SVO groups (p = 0.901). The predictors of SVO are shown in Table 3 . Table 3 Univariate analysis of factors associated with SVO Variable non-SVO (n = 80) SVO (n = 15) p-value Age 54.49 ± 15.62 48.53 ± 20.07 0.199 Gender Male Female 43 (53.75) 37 (46.25) 7 (46.67) 8 (53.33) 0.779 Body Weight 70.38 ± 12.27 67.20 ± 16.05 0.384 Side of Neuralgia Left Right 45 (56.25) 35 (43.75) 11 (73.33) 4 (26.67) 0.263 Sitting Surgical Position 35 (43.75) 6 (40.00) 0.004 SMT Enlargement 3 (3.75) 6 (40.00) < 0.001 Dolichoectatic Vertebrobasilar Artery 4 (5.00) 4 (26.67) 0.048 Operation Time (minutes) 83.96 ± 16.59 95.60 ± 24.30 0.024 ΔNRS Score 8.73 ± 1.17 8.67 ± 1.234 (5.00) 0.901 3.3 Multivariate Logistic Regression To identify the independent predictors of SVO, variables with p ≤ 0.05 in univariate analysis (surgical position, SMT enlargement, and a dolichoectatic VA) were included in the multivariate model. Independent predictors of SVO are presented in Table 4 . Table 4 Multivariate logistic regression analysis to identify independent predictors of SVO Predictor Odds Ratio (OR) 95% CI p-value SMT enlargement (≥ 4.8 mm) 12.5 2.8–55.3 < 0.001 Sitting Position 4.3 1.3–14.0 0.019 Dolichoectatic VA 3.9 1.1–13.8 0.040 The findings indicate that SMT enlargement is the strongest predictor of SVO, followed by surgical position and vascular anomaly. Impact of SMT Removal on Surgical and Clinical Outcomes Among the nine patients identified with SMT enlargement (≥ 4.8 mm), SMT removal was performed in six cases (66.7%) based on intraoperative assessment. In the remaining three cases, adequate exposure was achieved without the need for SMT removal. Pain relief was not significantly different between patients who underwent SMT removal and those who did not (p = 0.848). Both groups experienced marked improvement in pain, with postoperative NRS scores ≤ 1 (Table 5 ). Mean operative time in the SMT removal group was significantly longer than for patients without SMT removal (156 ± 22 min vs. 128 ± 19 min; p = 0.032) (Table 6 ). No intraoperative complications were directly attributed to SMT removal. Table 5 Summary of pain relief outcomes at the one-month postoperative follow-up Pain Relief Category Number of Patients Percentage (%) Complete Relief (NRS = 0, no meds) 79 83.2 Partial Relief (≥ 50% NRS reduction) 13 13.7 Poor Relief (< 50% reduction) 3 3.2 Table 6 Comparison of surgical and clinical outcomes in patients with and without SMT removal Variable Group with SMT Removal Group without SMT Removal p-value Number of Patients with SMT Enlargement 6 (66.7%) 3 (33.3%) — SMT Removal Performed Yes — — SMT Removal Not Performed — Yes — Mean Operative Time (minutes) 156 ± 22 128 ± 19 0.032 Mean Postoperative NRS Score 0.33 ± 0.52 0.29 ± 0.49 0.848 Intraoperative Complications None None — Discussion Traditionally, the SMT has been recognized as a major obstacle to MVD (Fig. 3 ). The SMT, located along the posterior petrous ridge, exhibits considerable morphological variability. When enlarged, it can restrict access to the CPA cistern, necessitating bone removal to improve visualization of the trigeminal nerve. Several prior studies have proposed morphometric thresholds (e.g., an SMT height ≥ 4.8 mm) that may predict the need for SMT drilling [ 2 , 6 , 7 ]. However, the findings of this study suggest that SMT hypertrophy is not the sole contributor to SVO. Multifactorial Nature of Surgical View Obstruction In this study, SMT enlargement, a dolichoectatic VA, and surgical sitting position were independently associated with the occurrence of SVO. These findings support a multifactorial model of surgical obstruction, in which both bony and soft tissue anatomical variations, as well as technical and positional factors, contribute to impaired visualization. A dolichoectatic vertebrobasilar artery is characterized by the elongation and tortuosity of the vertebrobasilar trunk (Fig. 4 ). It can displace or compress the trigeminal nerve and adjacent brainstem structures, complicating surgical access and limiting microsurgical maneuverability. This reinforces the need for careful preoperative neurovascular imaging to anticipate such challenges. The sitting position offers benefits such as gravity-assisted cerebellar relaxation but may also narrow the surgical corridor and limit dynamic microscope angulation, thereby reducing flexibility in optimizing the approach. This underscores the need for individualized positioning based on patient anatomy and surgeon preference. Interestingly, patient age, gender, body weight, and side of the lesion did not significantly influence the occurrence of SVO. This suggests that SVO is more closely related to local anatomical constraints and technical factors rather than patient demographics. Implications for SMT Removal and Visualization Strategies While SMT removal has traditionally been recommended in cases of prominent obstruction, the findings of this study support a more selective and nuanced approach. SMT drilling should be considered when standard maneuvers (e.g., cerebrospinal fluid release, cerebellar retraction, table tilt, microscope angulation) fail to achieve sufficient exposure (Fig. 5 ). The need for SMT removal should not be assumed from SMT height alone but assessed in the context of overall CPA geometry, the presence of vascular anomalies, and the surgeon’s experience. In short, this study supports a selective approach to SMT removal, guided by intraoperative evaluation rather than morphometric thresholds alone. Advancements in endoscopic assistance have also been reported to improve visualization in narrow CPA corridors without requiring bone removal [ 15 – 17 ]. The integration of microscopic and endoscopic techniques may provide enhanced illumination and clearer visualization, especially in cases where SVO is anticipated. Pain Outcomes and Operative Time Importantly, no significant difference was observed in short-term pain relief between patients who underwent SMT removal and those who did not. This suggests that SMT removal is not inherently associated with improved clinical outcomes but functions as an enabling step to facilitate safe and effective decompression when anatomical constraints are encountered. However, SMT removal was associated with significantly longer operative time, reflecting increased technical complexity. While this did not translate into higher complication rates in this study, prolonged operative duration has implications for patient safety, anesthetic exposure, and resource use. Comparison with Prior Literature These findings align with recent literature suggesting that SMT removal should be reserved for cases with documented visual obstruction and not performed routinely in all patients with SMT enlargement [ 6 – 8 , 13 ]. The decision to remove the SMT should be based on real-time anatomical assessment, surgeon experience, and the availability of adjunct visualization tools such as endoscopy. Clinical and Surgical Recommendations Based on the results of this study, the following practical recommendations are proposed: Preoperative planning should include high-resolution imaging to assess SMT size, vascular anatomy (e.g., dolichoectasia), and CPA cistern dimensions. Avoidance of the sitting position may reduce the likelihood of SVO in patients with borderline anatomy or dolichoectatic vessels. SMT removal should be reserved for cases where all non-invasive visualization strategies have been exhausted. Surgeons should be trained in endoscope-assisted MVD techniques to enhance visualization in anatomically constrained corridors. Finally, while this study highlights SMT enlargement, dolichoectatic vasculature, and patient positioning as major contributors to SVO, other anatomical and technical variables must also be considered. First, arachnoid adhesions—often encountered in patients with long-standing trigeminal neuralgia—may contribute to visual limitation even when the SMT is not enlarged. Dense arachnoid scarring can tether neurovascular structures and obscure the trigeminal nerve, making dissection more technically demanding. These adhesions may not be fully appreciated on preoperative imaging, but they can significantly impede visualization intraoperatively. Second, individual differences in CPA configuration, such as shallow cistern volume, narrow petroclival angle, or deep-seated nerve origin, can restrict the surgical corridor. Studies by Rao et al. and Rodriguez et al. have emphasized that even a modest SMT size can pose a challenge when accompanied by narrow CPA anatomy or a tight subarachnoid space [ 19 , 20 ]. The findings of this study support the notion that SVO is a dynamic outcome influenced by three-dimensional anatomical interplay, rather than a single bony or vascular measurement. Third, rotational brainstem shifts or asymmetries—especially in patients with long-standing neurovascular conflict or dolichoectatic arteries—may alter the relative location of the trigeminal nerve, further complicating surgical access. These subtle distortions are difficult to quantify but have real intraoperative implications. The authors acknowledge that the surgeon’s learning curve and technical proficiency play a critical role in mitigating SVO. An experienced surgeon may be able to achieve adequate exposure using standard retraction and microscope angulation in scenarios where others might opt for SMT removal. This underscores the need for surgeon-specific judgment, tailored training, and the use of adjunct tools such as angled endoscopy. Collectively, these alternative explanations reinforce that SVO is a multifactorial and context-sensitive challenge. It depends not only on the size of the SMT or vascular anatomy, but also on CPA morphology, soft tissue dynamics, and the surgeon’s skill in leveraging the available corridor. Conclusion SVO during MVD surgery for TGN was not solely attributable to SMT enlargement but still included a dolichoectatic vertebrobasilar artery and the use of the sitting surgical position. In contrast, patient-related variables such as age, gender, body weight, and the side of neuralgia were not predictive of intraoperative obstruction. The presence of SVO did not compromise short-term surgical efficacy in terms of postoperative pain relief. However, it was associated with longer operative times, reflecting increased technical complexity. These findings underscore the importance of thorough preoperative imaging and individualized intraoperative strategies to optimize surgical exposure. SMT removal should be selectively considered only after all less invasive visualization techniques have been exhausted. A comprehensive understanding of the multifactorial causes of SVO can improve operative planning, reduce intraoperative challenges, and enhance the overall safety and efficiency of MVD procedures. Limitations of the Study Several limitations should be acknowledged in this study: Small sample size SVO cases: Only 15 patients experienced SVO, which limits the statistical power to detect smaller associations and increases the risk of Type II error. Single-center retrospective design: The study was conducted at a single institution, which may limit the generalizability of the findings to other centers with different patient populations or surgical techniques. Short-term follow-up: Postoperative pain outcomes were assessed at one month, which may not accurately reflect long-term surgical success or recurrence rates. Subjective assessment of SVO: SVO was identified based on intraoperative surgeon assessment, which may introduce observer bias. Objective grading or blind evaluations were not employed. Operator variability: The complexity of MVD and variability in SVO management are influenced by the individual surgeon’s experience and technique. Although all procedures were performed by experienced neurosurgeons, individual differences may have affected intraoperative decisions, including whether to remove the SMT. Although SMT removal was recorded and analyzed, intraoperative video documentation or standardized grading of visualization difficulty was not employed, potentially introducing some subjectivity into the assessment of the necessity for SMT removal. Pain outcomes were assessed only at the one-month postoperative mark, which may not reflect the long-term durability of symptom relief. Future prospective studies should incorporate longitudinal follow-up (≥ one year) with standardized pain reporting tools and recurrence tracking. The follow-up was limited to one month in this study solely to determine whether surgical treatment would be effective in cases with SVO. The classification of SVO currently depends largely on the surgeon’s intraoperative judgment; future prospective studies incorporating intraoperative video scoring or third-party evaluations may help address this limitation. Future research involving larger, multicenter prospective cohorts, standardized definitions of SVO, and long-term outcome evaluation is warranted to validate these findings and refine surgical decision-making protocols. Declarations Funding This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. Human Ethics and Consent to participate This CRediT Authorship Contribution Statement Wongsirisuwan Methee Project administration; Writing – review and editing; Writing – original draft; Software; Methodology; Investigation; Formal analysis; Data curation; Conceptualization. Wangapakul Thitikan: Writing – review and editing. Rujimethapass Sujin: Writing – Methodology; Software. Conflicts Of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments None. References Headache Classification Committee of the International Headache Society (IHS). The international classification of headache disorders (2013), 3rd edition (beta version). 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Case Rep Neurol 7:167-172 Rao G, Primiani C, Sack J, Ashour R, Agazzi S, Van Loveren H (2017) To drill or not to drill: prominence of the suprameatal tubercle and its impact on microvascular decompression for trigeminal neuralgia—A proposed classification system. J Neurol Surg B 78:S1-S156 Rodriguez Rubio R, Xie W, Vigo V, Lee A, Tomasi OS, El-Sayed IH, Abla A (2021) Immersive surgical anatomy of the retrosigmoid approach . Cureus 13:e16068 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-7465273","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":509744233,"identity":"e531e2db-b70d-4db0-856c-eaf877b85d1f","order_by":0,"name":"Methee Wongsirisuwan","email":"","orcid":"","institution":"Rajavithi hospital","correspondingAuthor":false,"prefix":"","firstName":"Methee","middleName":"","lastName":"Wongsirisuwan","suffix":""},{"id":509744236,"identity":"3cbe5e92-979f-4d68-ae6f-9ba3b5669438","order_by":1,"name":"Thitikan Wangapakul","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIie3PMQuCQBTA8ScH53LkqhT4FS4Em8qvUghORzQaDQWtfYO+xE1C24mDy7UbLZpzYHtDaluDOjbcf3vH+8E7AJXqTxNAlwD6qR3IqB8gEKIhRDYYCB5C6s2amKwl0EuoMOKk2gT2zHrG5YstJhhQ8cg6SXsYm17Oa5/GkV8fhh2HdRD3S0KN35lrxhGqCcHjIcTjN9mQ/WDCVjwjDUn6iScQFZIGPpfModcoJRj1/MU6aGUVvv05T+U030Y7z9CPRdlFwM5/X1DXukqlUqkG9QH22UtUJ+u8cwAAAABJRU5ErkJggg==","orcid":"","institution":"Rajavithi hospital","correspondingAuthor":true,"prefix":"","firstName":"Thitikan","middleName":"","lastName":"Wangapakul","suffix":""},{"id":509744239,"identity":"836e7039-54a9-4a33-baca-6742ad34599d","order_by":2,"name":"Sujin Rujimethapass","email":"","orcid":"","institution":"Rajavithi hospital","correspondingAuthor":false,"prefix":"","firstName":"Sujin","middleName":"","lastName":"Rujimethapass","suffix":""}],"badges":[],"createdAt":"2025-08-26 17:38:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7465273/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7465273/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90903259,"identity":"da17f8a4-aa13-4867-a9cf-4d45e5b24780","added_by":"auto","created_at":"2025-09-09 12:48:14","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":119572,"visible":true,"origin":"","legend":"\u003cp\u003eMicrosurgical view through the retrosigmoid approach: (a) When the SMT is of normal size and the cerebellopontine angle (CPA) cistern is spacious, the entire trigeminal nerve—from the dorsal root entry zone (DREZ) to Meckel’s cave—is clearly visible. (b) However, in cases with a prominent or enlarged SMT, particularly when accompanied by a narrow CPA cistern, significant SVO can occur. In such situations, much of the trigeminal nerve may be obscured, making SMT removal necessary to achieve adequate exposure\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/f919fd9819d2d13312dd760b.jpg"},{"id":90903258,"identity":"bf76b3f7-e224-49db-a536-17a0b43f3017","added_by":"auto","created_at":"2025-09-09 12:48:14","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":54535,"visible":true,"origin":"","legend":"\u003cp\u003eDecision flowchart summarizing the intraoperative criteria for SMT removal\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/0a55f54923f97b6c400a4a24.jpg"},{"id":90905374,"identity":"eddce4a7-7bdc-4b18-9e11-bcd6f343e627","added_by":"auto","created_at":"2025-09-09 13:04:14","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":74072,"visible":true,"origin":"","legend":"\u003cp\u003eAxial MRI at both cerebellopontine angles shows a prominent SMT on the right side, measuring 7.2 mm in height, protruding into the surgical corridor and obstructing visualization of the cisternal part of the trigeminal nerve during MVD (DREZ = Dorsal Root Entry Zone of the trigeminal nerve)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/2045612ce586976e49312fdd.jpg"},{"id":90903261,"identity":"58058d6b-1908-4716-861b-4bc99403e275","added_by":"auto","created_at":"2025-09-09 12:48:14","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":66467,"visible":true,"origin":"","legend":"\u003cp\u003eMRI showing a dolichoectatic vertebrobasilar artery (asterisk) abutting the pons and compressing the root entry zone of the trigeminal nerve, contributing to SVO\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/b360eb66faab61e31aa5a1bc.jpg"},{"id":90903268,"identity":"b90bb57a-10c6-426d-8c04-d0cb8c5ba532","added_by":"auto","created_at":"2025-09-09 12:48:14","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":122812,"visible":true,"origin":"","legend":"\u003cp\u003eIntraoperative microscopic images. (a) Obstructed view of the cerebellopontine angle due to enlarged SMT (asterisk). (b) By adjusting/tilting the surgical microscope angle and operating table position, the DREZ of the trigeminal nerve (V) becomes visible; however, the SMT still obstructs the view of the entire cisternal portion. (c) Careful drilling of the SMT using a high-speed drill set to a low rotation speed (\u0026lt; 10,000 rpm) to minimize torque-induced kickback and reduce heat generation, thereby preventing thermal injury to the surrounding vital structures. (d) Improved exposure following partial SMT removal, revealing the cisternal portion of the trigeminal nerve and two offending vessels (arrow and double arrow)\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/1d45a0ba328fd8b572883c6d.jpg"},{"id":90907160,"identity":"89286172-81a3-4fd8-97c1-2fc185d1aead","added_by":"auto","created_at":"2025-09-09 13:20:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1370966,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7465273/v1/fd9ed833-2ff9-4658-84d2-d5ee7fbfbe9c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Independent Predictors of Surgical View Obstruction in Microvascular Decompression for Trigeminal Neuralgia: A Multifactorial Analysis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMicrovascular decompression (MVD) is a well-established surgical intervention for trigeminal neuralgia (TGN), particularly effective in cases with radiologically confirmed neurovascular compression (NVC). The retrosigmoid approach provides direct access to the dorsal root entry zone (DREZ), where NVC most commonly occurs. Despite its effectiveness, MVD can be technically challenging due to anatomical variations that obstruct the surgical corridor, impeding visualization and the manipulation of neurovascular structures.\u003c/p\u003e\u003cp\u003eOne of the most frequently cited anatomical impediments is the suprameatal tubercle (SMT)\u0026mdash;a bony prominence of variable size located at the posterior aspect of the petrous part of the temporal bone. In patients with a markedly enlarged SMT, visualization of the trigeminal nerve may be restricted (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), occasionally necessitating partial removal of the SMT to improve surgical exposure. Previous studies have highlighted the significance of SMT dimensions and proposed morphometric thresholds, such as a height\u0026thinsp;\u0026ge;\u0026thinsp;4.8 mm, to predict the need for SMT removal. However, SVO is not always attributable to SMT hypertrophy. Additional anatomical or positional factors may contribute to impaired visualization during MVD.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Methods and Materials","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy Design and Patient Selection\u003c/h2\u003e\u003cp\u003eInclusion criteria:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAdult patients diagnosed with classical TGN according to the International Headache Society (IHS) criteria [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eUndergoing MVD via the retrosigmoid approach between January 2015\u0026ndash;June 2024.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eExclusion criteria:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003ePrevious posterior fossa surgery on the same side.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eTGN secondary to intracranial tumors or other non-vascular compressive lesions.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eHistory of Gamma Knife radiosurgery.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eUse of alternative surgical approaches (e.g., subtemporal or anterior petrosal).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eDefinition of Surgical View Obstruction (SVO)\u003c/h3\u003e\n\u003cp\u003eSVO is defined as intraoperative difficulty in adequately visualizing the trigeminal nerve from DREZ to the entrance of Meckel\u0026rsquo;s cave during MVD, despite standard exposure techniques. The determination of SVO was based on the combination of intraoperative findings and preoperative imaging and categorized according to defined anatomical and technical criteria.\u003c/p\u003e\u003cp\u003eSVO was considered present when any of the following conditions were met:\u003c/p\u003e\n\u003ch3\u003e1. Bony obstruction:\u003c/h3\u003e\n\u003cp\u003e\u003cul\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eProminent suprameatal tubercle (SMT) with a height\u0026thinsp;\u0026ge;\u0026thinsp;4.8 mm on preoperative CT imaging, consistent with the criteria proposed by Iwasaki et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSMT protruding into the surgical corridor and requiring bone drilling for adequate exposure.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ul\u003e\u003c/p\u003e\n\u003ch3\u003e2. Vascular obstruction:\u003c/h3\u003e\n\u003cp\u003e\u003cul\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePresence of a dolichoectatic vertebrobasilar artery (VA) or other tortuous/bulky vessels that displaced or obscured the trigeminal nerve.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eOffending vessel requiring complex retraction or manipulation to access the NVC.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ul\u003e\u003c/p\u003e\n\u003ch3\u003e3. Cistern crowding or technical limitations:\u003c/h3\u003e\n\u003cp\u003e\u003cul\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eNarrow cerebellopontine angle (CPA) cistern (subjectively tight operative field despite CSF release).\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eIntraoperative inability to achieve an adequate surgical corridor through standard techniques (e.g., table tilt, microscope angulation, cerebellar retraction) necessitating additional adjustments or SMT removal.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eFor improved granularity, SVO was further classified into three grades based on intraoperative impact (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eProposed classification of SVO\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDefinition\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade I \u003c/p\u003e\u003cp\u003e(Mild)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSlight visual limitation resolved by standard adjustments (e.g., CSF drainage, microscope angle); no SMT removal needed.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade II (Moderate)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eObstructed view requiring additional maneuvers such as table repositioning, cerebellar retraction, or angled endoscopy; SMT removal not required.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade III \u003c/p\u003e\u003cp\u003e(Severe)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSignificant obstruction requiring SMT drilling and/or advanced dissection due to bony prominence or dolichoectatic vasculature.\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\u003eOnly patients meeting the criteria for Grades II or III were classified as having significant SVO for statistical analysis.\u003c/p\u003e\u003cp\u003eThe decision flowchart summarizing intraoperative criteria for SMT removal is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eData Collection\u003c/h2\u003e\u003cp\u003eDemographic, clinical, radiological, and intraoperative variables were extracted, including:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAge, gender, body weight, and side of the lesion\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePresence of SMT enlargement on imaging\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIntraoperative position (supine vs. sitting)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eType of vascular offender\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eOperation time\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePresence of SVO\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePre and postoperative numeric rating scale (NRS) for pain\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003ePostoperative pain outcomes were assessed at the first outpatient visit within one month after surgery.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eEthical Considerations\u003c/h3\u003e\n\u003cp\u003eThe study protocol was approved by the Rajavithi Institutional Review Board (IRB 106/2567). Informed consent was waived due to the retrospective nature of the study and use of anonymized data. All data were handled in accordance with ethical and privacy standards.\u003c/p\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eData were analyzed using GraphPad Prism 8 (GraphPad Software Inc.). Continuous variables were presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation, and categorical variables as counts and percentages. The normality of distribution was assessed using the Shapiro-Wilk test.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eUnivariate analysis was performed using Student\u0026rsquo;s t-test or Mann\u0026ndash;Whitney U test for continuous variables and chi-square or Fisher\u0026rsquo;s exact test for categorical variables.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMultivariate analysis using binary logistic regression was conducted to identify independent predictors of SVO. Variables with a p\u0026thinsp;\u0026le;\u0026thinsp;0.05 in univariate analysis were included in the regression model.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003ePatient Characteristics\u003c/h2\u003e\u003cp\u003eA total of 95 patients with classical TGN underwent microvascular decompression (MVD) via the retrosigmoid approach. The mean age was 55.8\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7 years, and 56.8% were female. Most procedures were performed in the supine position (74.74%), with the remaining in the sitting position (25.26%). Nine patients (9.47%) had SMT enlargement (\u0026ge;\u0026thinsp;4.8 mm).\u003c/p\u003e\u003cp\u003eThe superior cerebellar artery (SCA) was the most common offending vessel (71.58%), followed by veins (15.79%) and the presence of a dolichoectatic vertebrobasilar artery (9.47%). The mean preoperative NRS score was 8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64, which improved significantly to 0.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83 postoperatively. Demographic and operative data are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePatient demographics and intraoperative characteristics\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eValue\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal Patients\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Age (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e55.8\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e56.8%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSupine Position (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e74.74%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSitting Position (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25.26%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSMT Enlargement (\u0026ge;\u0026thinsp;4.8 mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9 (9.47%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDolichoectatic Vertebrobasilar Artery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9 (9.47%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSCA as Offending Vessel (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e71.58%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Pre-op NRS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Post-op NRS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.83\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eIncidence and Predictors of Surgical View Obstruction (SVO)\u003c/h2\u003e\u003cp\u003eSVO was documented in 15 patients (15.79%). The positive factors related to SVO were sitting position (p\u0026thinsp;=\u0026thinsp;0.004), SMT enlargement (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and the presence of a dolichoectatic vertebrobasilar artery (p\u0026thinsp;=\u0026thinsp;0.048).\u003c/p\u003e\u003cp\u003eOperation time was significantly longer in patients with SVO (p\u0026thinsp;=\u0026thinsp;0.024). Other factors, including age, gender, side of involvement, and body weight, were not significantly associated with SVO (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003eThere was no significant difference in the degree of pain reduction (ΔNRS score) between the SVO and non-SVO groups (p\u0026thinsp;=\u0026thinsp;0.901). The predictors of SVO are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eUnivariate analysis of factors associated with SVO\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\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\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003enon-SVO (n\u0026thinsp;=\u0026thinsp;80)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSVO (n\u0026thinsp;=\u0026thinsp;15)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e54.49\u0026thinsp;\u0026plusmn;\u0026thinsp;15.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48.53\u0026thinsp;\u0026plusmn;\u0026thinsp;20.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.199\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGender\u003c/p\u003e\u003cp\u003eMale\u003c/p\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43 (53.75)\u003c/p\u003e\u003cp\u003e37 (46.25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7 (46.67)\u003c/p\u003e\u003cp\u003e8 (53.33)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.779\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody Weight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70.38\u0026thinsp;\u0026plusmn;\u0026thinsp;12.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e67.20\u0026thinsp;\u0026plusmn;\u0026thinsp;16.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.384\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSide of Neuralgia\u003c/p\u003e\u003cp\u003eLeft\u003c/p\u003e\u003cp\u003eRight\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e45 (56.25)\u003c/p\u003e\u003cp\u003e35 (43.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11 (73.33)\u003c/p\u003e\u003cp\u003e4 (26.67)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.263\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSitting Surgical Position\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35 (43.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6 (40.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003e0.004\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSMT Enlargement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (3.75)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6 (40.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003e\u0026lt;\u0026thinsp;0.001\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDolichoectatic Vertebrobasilar Artery\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (5.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4 (26.67)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003e0.048\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation Time (minutes)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e83.96\u0026thinsp;\u0026plusmn;\u0026thinsp;16.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95.60\u0026thinsp;\u0026plusmn;\u0026thinsp;24.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.024\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eΔNRS Score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.73\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.234 (5.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.901\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003ch2\u003e3.3 Multivariate Logistic Regression\u003c/h2\u003e\u003cp\u003eTo identify the independent predictors of SVO, variables with p\u0026thinsp;\u0026le;\u0026thinsp;0.05 in univariate analysis (surgical position, SMT enlargement, and a dolichoectatic VA) were included in the multivariate model. Independent predictors of SVO are presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMultivariate logistic regression analysis to identify independent predictors of SVO\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePredictor\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOdds Ratio (OR)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95% CI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSMT enlargement (\u0026ge;\u0026thinsp;4.8 mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.8\u0026ndash;55.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSitting Position\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.3\u0026ndash;14.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.019\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDolichoectatic VA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.1\u0026ndash;13.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.040\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\u003eThe findings indicate that SMT enlargement is the strongest predictor of SVO, followed by surgical position and vascular anomaly.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eImpact of SMT Removal on Surgical and Clinical Outcomes\u003c/h2\u003e\u003cp\u003eAmong the nine patients identified with SMT enlargement (\u0026ge;\u0026thinsp;4.8 mm), SMT removal was performed in six cases (66.7%) based on intraoperative assessment. In the remaining three cases, adequate exposure was achieved without the need for SMT removal.\u003c/p\u003e\u003cp\u003ePain relief was not significantly different between patients who underwent SMT removal and those who did not (p\u0026thinsp;=\u0026thinsp;0.848). Both groups experienced marked improvement in pain, with postoperative NRS scores\u0026thinsp;\u0026le;\u0026thinsp;1 (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eMean operative time in the SMT removal group was significantly longer than for patients without SMT removal (156\u0026thinsp;\u0026plusmn;\u0026thinsp;22 min vs. 128\u0026thinsp;\u0026plusmn;\u0026thinsp;19 min; p\u0026thinsp;=\u0026thinsp;0.032) (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eNo intraoperative complications were directly attributed to SMT removal.\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\u003eSummary of pain relief outcomes at the one-month postoperative follow-up\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePain Relief Category\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNumber of Patients\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePercentage (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComplete Relief (NRS\u0026thinsp;=\u0026thinsp;0, no meds)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e83.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePartial Relief (\u0026ge;\u0026thinsp;50% NRS reduction)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e13.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePoor Relief (\u0026lt;\u0026thinsp;50% reduction)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.2\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\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of surgical and clinical outcomes in patients with and without SMT removal\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup with SMT Removal\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup without SMT Removal\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNumber of Patients with SMT Enlargement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6 (66.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (33.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSMT Removal Performed\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSMT Removal Not Performed\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Operative Time (minutes)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e156\u0026thinsp;\u0026plusmn;\u0026thinsp;22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e128\u0026thinsp;\u0026plusmn;\u0026thinsp;19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Postoperative NRS Score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.848\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative Complications\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026mdash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eTraditionally, the SMT has been recognized as a major obstacle to MVD (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The SMT, located along the posterior petrous ridge, exhibits considerable morphological variability. When enlarged, it can restrict access to the CPA cistern, necessitating bone removal to improve visualization of the trigeminal nerve. Several prior studies have proposed morphometric thresholds (e.g., an SMT height\u0026thinsp;\u0026ge;\u0026thinsp;4.8 mm) that may predict the need for SMT drilling [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, the findings of this study suggest that SMT hypertrophy is not the sole contributor to SVO.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003eMultifactorial Nature of Surgical View Obstruction\u003c/h2\u003e\u003cp\u003eIn this study, SMT enlargement, a dolichoectatic VA, and surgical sitting position were independently associated with the occurrence of SVO. These findings support a multifactorial model of surgical obstruction, in which both bony and soft tissue anatomical variations, as well as technical and positional factors, contribute to impaired visualization.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eA dolichoectatic vertebrobasilar artery is characterized by the elongation and tortuosity of the vertebrobasilar trunk (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). It can displace or compress the trigeminal nerve and adjacent brainstem structures, complicating surgical access and limiting microsurgical maneuverability. This reinforces the need for careful preoperative neurovascular imaging to anticipate such challenges.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe sitting position offers benefits such as gravity-assisted cerebellar relaxation but may also narrow the surgical corridor and limit dynamic microscope angulation, thereby reducing flexibility in optimizing the approach. This underscores the need for individualized positioning based on patient anatomy and surgeon preference.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eInterestingly, patient age, gender, body weight, and side of the lesion did not significantly influence the occurrence of SVO. This suggests that SVO is more closely related to local anatomical constraints and technical factors rather than patient demographics.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003eImplications for SMT Removal and Visualization Strategies\u003c/h2\u003e\u003cp\u003eWhile SMT removal has traditionally been recommended in cases of prominent obstruction, the findings of this study support a more selective and nuanced approach. SMT drilling should be considered when standard maneuvers (e.g., cerebrospinal fluid release, cerebellar retraction, table tilt, microscope angulation) fail to achieve sufficient exposure (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The need for SMT removal should not be assumed from SMT height alone but assessed in the context of overall CPA geometry, the presence of vascular anomalies, and the surgeon\u0026rsquo;s experience. In short, this study supports a selective approach to SMT removal, guided by intraoperative evaluation rather than morphometric thresholds alone.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAdvancements in endoscopic assistance have also been reported to improve visualization in narrow CPA corridors without requiring bone removal [\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The integration of microscopic and endoscopic techniques may provide enhanced illumination and clearer visualization, especially in cases where SVO is anticipated.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003ePain Outcomes and Operative Time\u003c/h2\u003e\u003cp\u003eImportantly, no significant difference was observed in short-term pain relief between patients who underwent SMT removal and those who did not. This suggests that SMT removal is not inherently associated with improved clinical outcomes but functions as an enabling step to facilitate safe and effective decompression when anatomical constraints are encountered.\u003c/p\u003e\u003cp\u003eHowever, SMT removal was associated with significantly longer operative time, reflecting increased technical complexity. While this did not translate into higher complication rates in this study, prolonged operative duration has implications for patient safety, anesthetic exposure, and resource use.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003eComparison with Prior Literature\u003c/h2\u003e\u003cp\u003eThese findings align with recent literature suggesting that SMT removal should be reserved for cases with documented visual obstruction and not performed routinely in all patients with SMT enlargement [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The decision to remove the SMT should be based on real-time anatomical assessment, surgeon experience, and the availability of adjunct visualization tools such as endoscopy.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003eClinical and Surgical Recommendations\u003c/h2\u003e\u003cp\u003eBased on the results of this study, the following practical recommendations are proposed:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePreoperative planning should include high-resolution imaging to assess SMT size, vascular anatomy (e.g., dolichoectasia), and CPA cistern dimensions.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAvoidance of the sitting position may reduce the likelihood of SVO in patients with borderline anatomy or dolichoectatic vessels.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSMT removal should be reserved for cases where all non-invasive visualization strategies have been exhausted.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSurgeons should be trained in endoscope-assisted MVD techniques to enhance visualization in anatomically constrained corridors.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eFinally, while this study highlights SMT enlargement, dolichoectatic vasculature, and patient positioning as major contributors to SVO, other anatomical and technical variables must also be considered.\u003c/p\u003e\u003cp\u003eFirst, arachnoid adhesions\u0026mdash;often encountered in patients with long-standing trigeminal neuralgia\u0026mdash;may contribute to visual limitation even when the SMT is not enlarged. Dense arachnoid scarring can tether neurovascular structures and obscure the trigeminal nerve, making dissection more technically demanding. These adhesions may not be fully appreciated on preoperative imaging, but they can significantly impede visualization intraoperatively.\u003c/p\u003e\u003cp\u003eSecond, individual differences in CPA configuration, such as shallow cistern volume, narrow petroclival angle, or deep-seated nerve origin, can restrict the surgical corridor. Studies by Rao et al. and Rodriguez et al. have emphasized that even a modest SMT size can pose a challenge when accompanied by narrow CPA anatomy or a tight subarachnoid space [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The findings of this study support the notion that SVO is a dynamic outcome influenced by three-dimensional anatomical interplay, rather than a single bony or vascular measurement.\u003c/p\u003e\u003cp\u003eThird, rotational brainstem shifts or asymmetries\u0026mdash;especially in patients with long-standing neurovascular conflict or dolichoectatic arteries\u0026mdash;may alter the relative location of the trigeminal nerve, further complicating surgical access. These subtle distortions are difficult to quantify but have real intraoperative implications.\u003c/p\u003e\u003cp\u003eThe authors acknowledge that the surgeon\u0026rsquo;s learning curve and technical proficiency play a critical role in mitigating SVO. An experienced surgeon may be able to achieve adequate exposure using standard retraction and microscope angulation in scenarios where others might opt for SMT removal. This underscores the need for surgeon-specific judgment, tailored training, and the use of adjunct tools such as angled endoscopy.\u003c/p\u003e\u003cp\u003eCollectively, these alternative explanations reinforce that SVO is a multifactorial and context-sensitive challenge. It depends not only on the size of the SMT or vascular anatomy, but also on CPA morphology, soft tissue dynamics, and the surgeon\u0026rsquo;s skill in leveraging the available corridor.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eSVO during MVD surgery for TGN was not solely attributable to SMT enlargement but still included a dolichoectatic vertebrobasilar artery and the use of the sitting surgical position. In contrast, patient-related variables such as age, gender, body weight, and the side of neuralgia were not predictive of intraoperative obstruction.\u003c/p\u003e\u003cp\u003eThe presence of SVO did not compromise short-term surgical efficacy in terms of postoperative pain relief. However, it was associated with longer operative times, reflecting increased technical complexity. These findings underscore the importance of thorough preoperative imaging and individualized intraoperative strategies to optimize surgical exposure. SMT removal should be selectively considered only after all less invasive visualization techniques have been exhausted.\u003c/p\u003e\u003cp\u003eA comprehensive understanding of the multifactorial causes of SVO can improve operative planning, reduce intraoperative challenges, and enhance the overall safety and efficiency of MVD procedures.\u003c/p\u003e\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\u003ch2\u003eLimitations of the Study\u003c/h2\u003e\u003cp\u003eSeveral limitations should be acknowledged in this study:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSmall sample size SVO cases: Only 15 patients experienced SVO, which limits the statistical power to detect smaller associations and increases the risk of Type II error.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSingle-center retrospective design: The study was conducted at a single institution, which may limit the generalizability of the findings to other centers with different patient populations or surgical techniques.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eShort-term follow-up: Postoperative pain outcomes were assessed at one month, which may not accurately reflect long-term surgical success or recurrence rates.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSubjective assessment of SVO: SVO was identified based on intraoperative surgeon assessment, which may introduce observer bias. Objective grading or blind evaluations were not employed.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eOperator variability: The complexity of MVD and variability in SVO management are influenced by the individual surgeon\u0026rsquo;s experience and technique. Although all procedures were performed by experienced neurosurgeons, individual differences may have affected intraoperative decisions, including whether to remove the SMT.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAlthough SMT removal was recorded and analyzed, intraoperative video documentation or standardized grading of visualization difficulty was not employed, potentially introducing some subjectivity into the assessment of the necessity for SMT removal.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003ePain outcomes were assessed only at the one-month postoperative mark, which may not reflect the long-term durability of symptom relief. Future prospective studies should incorporate longitudinal follow-up (\u0026ge;\u0026thinsp;one year) with standardized pain reporting tools and recurrence tracking. The follow-up was limited to one month in this study solely to determine whether surgical treatment would be effective in cases with SVO.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe classification of SVO currently depends largely on the surgeon\u0026rsquo;s intraoperative judgment; future prospective studies incorporating intraoperative video scoring or third-party evaluations may help address this limitation.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003eFuture research involving larger, multicenter prospective cohorts, standardized definitions of SVO, and long-term outcome evaluation is warranted to validate these findings and refine surgical decision-making protocols.\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHuman Ethics and Consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT Authorship Contribution Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWongsirisuwan Methee\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProject administration; Writing – review and editing; Writing – original draft; Software; Methodology; Investigation; Formal analysis; Data curation; Conceptualization. \u003cstrong\u003eWangapakul Thitikan:\u003c/strong\u003e Writing – review and editing. \u003cstrong\u003eRujimethapass Sujin:\u003c/strong\u003e Writing – Methodology; Software.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts Of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eHeadache Classification Committee of the International Headache Society (IHS). The international classification of headache disorders (2013), 3rd edition (beta version). \u003cem\u003eCephalalgia\u003c/em\u003e 33:629-808. https://ichd-3.org/3-trigeminal-autonomic-cephalalgias/\u003c/li\u003e\n \u003cli\u003eIwasaki K, Uezato M, Nishida N, Yoshimoto N, Kitamura K, Gomi M, Hashikata H, Sasaki I, Toda H (2024);2198-8279 Surgical nuances and predictors of requirement for suprameatal tubercle removal in microvascular decompression for trigeminal neuralgia. J Neurol Surg B 85(Suppl 2):e38-e45\u003c/li\u003e\n \u003cli\u003eJensen MP, Karoly P, Braver S (1986) The measurement of clinical pain intensity: a comparison of six methods. Pain 27:117-126\u003c/li\u003e\n \u003cli\u003eReyna H, Reyna S, Espinoza J, Lopez E, Mendez D (2020) Classification of the suprameatal tubercle and morphometric analysis with surgical approach to the temporal bone. J Neurol Surg B 81(S 01):S1-S272\u003c/li\u003e\n \u003cli\u003eOiwa Y, Hirohata Y, Okumura H, Yamaga H, Takayama M, Terui K, Yako R (2013) Bone drilling in microvascular decompression for trigeminal neuralgia: high morphological variety of the petrous bone. No Shinkei Geka Neurol Surg 41:601-607. PMID: 23824350\u003c/li\u003e\n \u003cli\u003eReyna Mendez H, Espinosa Mora JA, Ubaldo Reyes L, Angeles Castellanos A, Mora Maga\u0026ntilde;a I, Segura Lozano MA, Blue R, Lee JY, Mendez Rosito D (2020) Suprameatal tubercle classification; its implementation on clinical cases. Arch Neurosurg 1:Article 6. https://www.ansjournal.org/home/vol1/iss1/6\u003c/li\u003e\n \u003cli\u003eRennert RC, Brandel MG, Stephens ML, Rodriguez A, Morris TW, Day JD (2021) Surgical relevance of the suprameatal tubercle during superior petrosal vein-sparing trigeminal nerve microvascular decompression. Oper Neurosurg 20:E410-E416\u003c/li\u003e\n \u003cli\u003eChanda A, Nanda A (2006) Retrosigmoid intradural suprameatal approach: advantages and disadvantages from an anatomical perspective. Neurosurgery 59(Suppl 1):ONS1-6; discussion ONS1\u003c/li\u003e\n \u003cli\u003eIbrahim B, Muhsen BA, Najera E, Borghei-Razavi H, Adada B (2021) Case report of unusual cause of trigeminal neuralgia: trigeminal neuralgia secondary to enlarged suprameatal tubercle. Ann Med Surg (Lond) 66:102308\u003c/li\u003e\n \u003cli\u003eMalli A, Melissaris S, Charitos D, Zlatanos C, Kasapas K, Georgakoulias N (2021) Enlarged suprameatal Tubercle as the primary cause of trigeminal neuralgia: our 5-year experience of cases. Brain Spine 1:100717. https://doaj.org/article/2d663b719581485f9f3ea7852470d489\u003c/li\u003e\n \u003cli\u003eAgarwal N, Kumar A, Singh P, Chandra PS, Kale SS (2022) Suprameatal extension of retrosigmoid approach in microvascular decompression for trigeminal neuralgia with petrous endostosis: case report and literature review. Neurol India 70:1240-1243\u003c/li\u003e\n \u003cli\u003eHirata S, Kobayashi M, Kamamoto D, Kosugi K, Yoshida K, Fujimaki T (2019) Trigeminal neuralgia due to petrosal bone deformity. World Neurosurg 126:79-82\u003c/li\u003e\n \u003cli\u003eInoue T, Goto Y, Prasetya M, Fukushima T (2020) Resection of the suprameatal tubercle in microvascular decompression for trigeminal neuralgia. Acta Neurochir (Wien) 162:1089-1094\u003c/li\u003e\n \u003cli\u003eMoreira-Holguin JC, Revuelta-Gutierrez R, Monroy-Sosa A, Almeida-Navarro S (2015) Suprameatal extension of retrosigmoid approach for microvascular decompression of trigeminal nerve: case report. 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Case Rep Neurol 7:167-172\u003c/li\u003e\n \u003cli\u003eRao G, Primiani C, Sack J, Ashour R, Agazzi S, Van Loveren H (2017) To drill or not to drill: prominence of the suprameatal tubercle and its impact on microvascular decompression for trigeminal neuralgia\u0026mdash;A proposed classification system. J Neurol Surg B 78:S1-S156\u003c/li\u003e\n \u003cli\u003eRodriguez Rubio R, Xie W, Vigo V, Lee A, Tomasi OS, El-Sayed IH, Abla A (2021) Immersive surgical anatomy of the retrosigmoid approach\u003cem\u003e.\u0026nbsp;\u003c/em\u003eCureus 13:e16068\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"trigeminal neuralgia, microvascular decompression, suprameatal tubercle, surgical view obstruction, dolichoectasia, retrosigmoid approach","lastPublishedDoi":"10.21203/rs.3.rs-7465273/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7465273/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction:\u003c/h2\u003e\u003cp\u003eMicrovascular decompression (MVD) is an effective surgical treatment for trigeminal neuralgia (TGN), but intraoperative anatomical variations may obstruct the surgical view and complicate exposure of the neurovascular conflict (NVC). While suprameatal tubercle (SMT) enlargement is a known cause of surgical view obstruction (SVO), other contributory factors remain underexplored. This study investigates the additional anatomical and technical factors associated with SVO during MVD and examines whether SVO affects postoperative pain outcomes.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eA retrospective review was conducted on 95 patients who underwent MVD for TGN between January 2015 and June 2024. Demographic data, radiographic findings, intraoperative variables, and pain scores were analyzed. Univariate and multivariate statistical analyses were performed to identify factors associated with SVO and postoperative pain relief.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eSVO was observed in 15 patients (15.79%). Multivariate logistic regression identified three independent predictors of SVO: SMT enlargement (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), presence of a dolichoectatic vertebrobasilar artery (p\u0026thinsp;=\u0026thinsp;0.040), and sitting surgical position (p\u0026thinsp;=\u0026thinsp;0.019). Although SVO was associated with a significantly longer operative time (p\u0026thinsp;=\u0026thinsp;0.024), it did not adversely affect short-term pain relief (p\u0026thinsp;=\u0026thinsp;0.901).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eSVO during MVD for TGN is multifactorial and not limited to SMT enlargement. Dolichoectatic vascular anatomy and the sitting surgical position also contribute significantly to SVO. Thorough preoperative imaging and individualized intraoperative strategies are essential for optimizing visualization and improving surgical efficiency.\u003c/p\u003e","manuscriptTitle":"Independent Predictors of Surgical View Obstruction in Microvascular Decompression for Trigeminal Neuralgia: A Multifactorial Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-09 12:48:09","doi":"10.21203/rs.3.rs-7465273/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b4d11621-a7b9-4864-9fc7-4e2807ee2b39","owner":[],"postedDate":"September 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-09T12:56:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-09 12:48:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7465273","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7465273","identity":"rs-7465273","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}