Risk Factors for Sinking Skin Flap Syndrome After Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage

Risk Factors for Sinking Skin Flap Syndrome After Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage | 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 Sinking Skin Flap Syndrome After Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage Özde ŞENOL AKBULUT, Mustafa Sedar Bölük, Bilal Bahadır Akbulut, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8376162/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 Background To evaluate clinical, radiological, and procedural risk factors for sinking skin flap syndrome (SSFS) following decompressive craniectomy (DC) in a homogenous cohort of aneurysmal subarachnoid hemorrhage (aSAH) patients. Methods Patients who underwent DC for aSAH between 2014–2024 were retrospectively reviewed. Demographic variables, hemorrhage severity scores, CSF diversion characteristics, craniectomy morphometry, and radiological measurements were compared between patients with and without SSFS. Time-to-event analysis was used to characterize SSFS onset. Mann–Whitney U and Fisher’s exact tests were applied for group comparisons. A multivariable logistic regression model was constructed including craniectomy area and CSF diversion duration. Results Fifteen patients met inclusion criteria; four (27%) developed SSFS. Baseline demographics, hemorrhage grades, and aneurysm features were comparable between groups. SSFS patients had significantly larger craniectomy areas and exhibited greater flap sinking and paradoxical midline shift. CSF diversion duration was longer in SSFS patients but not statistically significant. SSFS occurred at a median of 265 days after DC, and all affected patients showed neurological improvement following cranioplasty. Non-SSFS patients had adequate at-risk follow-up without events. Conclusion In aSAH patients, larger craniectomy area is a strong predictor of SSFS, while prolonged CSF diversion demonstrates a non-significant trend toward increased risk. Diagnostic delays in the complex aSAH postoperative course may mask true onset. Radiological sinking alone is insufficient for diagnosis, as asymptomatic flap depression also occurred. Improved awareness is required to avoid both under- and overdiagnosis, and larger multicenter studies are needed to define clinical and radiological thresholds for SSFS. Sinking Skin Flap Syndrome Decompressive Craniectomy Aneurysmal Subarachnoid Hemorrhage Cerebrospinal Fluid Diversion Cranioplasty Cerebrospinal Fluid Drainage Figures Figure 1 Introduction Sinking Skin Flap Syndrome (SSFS) is a delayed complication following decompressive craniectomy (DC), characterized by neurologic deterioration associated with atmospheric pressure transmission through the skull defect; widely conflated with the Syndrome of Trephined, originally described by Grant and Norcross in 1939. ( 1 ) The term "sinking skin flap syndrome" was first proposed by Yamaura et al. in 1977 after demonstrating symptom reversibility following cranioplasty ( 2 ). Although uncommon, its incidence remains inconsistently reported, ranging from 7.8% to 28% according to recent reviews. ( 3 ) Pathophysiologically, SSFS is thought to result from alterations in cerebrospinal fluid dynamics, impaired cerebral blood flow, and direct atmospheric pressure effects in the absence of a rigid cranial vault. This conversion of the cranium from a “closed box” to an “open box” leads to a vulnerable equilibrium, predisposing to neurological dysfunction and, in some cases, paradoxical herniation ( 3 , 4 ). Most proposed SSFS risk factors such as craniectomy size, CSF diversion, brain-edema dynamics, and timing of reconstruction, have been evaluated in heterogeneous decompressive craniectomy cohorts, often combining traumatic, ischemic, and other etiologies. ( 4 – 7 ) To date, no study has specifically examined SSFS within a homogenous aneurysmal subarachnoid hemorrhage (aSAH) population, likely because both DC in aSAH ( 8 ) and subsequent SSFS are relatively uncommon events, making large dedicated cohorts difficult to assemble. Given the distinct intracranial dynamics associated with aSAH, including hemorrhage burden, early brain injury, fluctuating intracranial compliance, and the high incidence of hydrocephalus ( 9 ), a focused analysis within this subgroup may provide additional insight. For this reason, we investigated SSFS exclusively in aSAH patients, evaluating both previously proposed risk factors and parameters potentially specific to the aSAH disease process. Methods Statement of Ethics This study was conducted in accordance with the principles outlined in the Declaration of Helsinki. Ethical approval was obtained from the local ethics committee (25-12T/70). Informed consent was obtained for every patient prior to the surgery. Study Population and Clinical Variables Patients who underwent decompressive hemicraniectomy for aneurysmal subarachnoid hemorrhage (aSAH) between 2014 and 2024 were retrospectively evaluated. Only standard hemicraniectomies were included. Atypical craniectomy types, extradural aneurysms, and patients who survived less than one month after aneurysm treatment were excluded as SSFS has been consistently reported to develop at least several weeks after decompressive craniectomy, and these patients would not have provided adequate time-to-event observation. ( 1 , 6 , 10 ) Demographic and clinical variables included age, sex, ASA score, admission Glasgow Coma Scale (GCS), and pre-DC modified Rankin Scale (mRS). aSAH severity was characterized using established grading systems: Hunt–Hess and WFNS scores to describe initial clinical severity ( 11 ), Fisher grade to quantify hemorrhage load, reflecting both its known association with vasospasm risk and its impact on intracranial compliance dynamics ( 12 ), and Yasargil aneurysm grade to capture aneurysm rupture complexity ( 13 ). Aneurysm location and treatment modality (microsurgical clipping or endovascular treatment) were also recorded. Post-decompressive course variables included Glasgow Outcome Scale (GOS), mRS at last follow-up, ICU length of stay, and time-to-event data regarding SSFS development. SSFS onset was treated as the event of interest. For patients who underwent cranioplasty or had no SSFS during follow-up, the interval from decompressive craniectomy to the date of cranioplasty or last available clinical/radiological assessment was recorded as censoring time, as these patients remained at risk for SSFS until that point. Cerebrospinal fluid (CSF) diversion was documented by presence of lumbar drainage, external ventricular drainage, or permanent shunting, and the total duration of diversion was calculated as the cumulative number of days during which any diversion system was in place. Radiological Assessment For radiological analysis, craniectomy surface area was measured using Meshmixer (Autodesk Inc., San Rafael, CA, USA; version 3.5). Preoperative and postoperative CT scans were converted into overlapping 3D models, and the craniectomy region was manually isolated to obtain surface area values. The most recent CT prior to cranioplasty, or the latest available follow-up CT in patients without cranioplasty, was evaluated for skin flap level (sunken, isolevel, or bulging), degree of displacement of the skin flap relative to the original bone margin, and presence and magnitude of midline shift. Statistical Analysis Continuous variables (e.g., age, ICU stay, craniectomy area, CSF diversion duration, radiological measurements) and ordinal variables (Fisher grade, Hunt–Hess grade, WFNS grade, Yasargil aneurysm grade) were compared between patients with and without SSFS using the Mann–Whitney U test, given the small sample size and non-normal distribution. Categorical variables, such as presence of comorbidity, CSF diversion, or radiological midline shift, were analyzed using Fisher’s exact test. Because SSFS represents a time-dependent outcome, a time-to-event framework was applied to describe the interval between decompressive craniectomy and either SSFS onset (event) or censoring. SSFS onset was treated as the event of interest. For patients without SSFS, the interval from craniectomy to cranioplasty or last available follow-up was recorded as censoring time. Kaplan–Meier estimates were used descriptively to illustrate SSFS-free survival over time. A multivariable logistic regression model was constructed to evaluate independent associations with SSFS, including craniectomy area and CSF diversion duration as covariates. Odds ratios, 95% confidence intervals, and model significance were reported. A p-value < 0.05 was considered statistically significant. Results A total of 28 patients were screened, and 15 met eligibility criteria for the final analysis. All aneurysms in the study cohort were treated with microsurgical clipping; no patient underwent endovascular treatment. Four patients (27%) developed sinking flap syndrome (SSFS), while eleven patients constituted the control group. Baseline Characteristics Systemic and hemorrhage-severity indicators did not differ significantly between groups. Median age was comparable (45 years in the control group vs 49.5 years in the SSFS group), as was sex distribution. Aneurysm locations were typical for high-grade aSAH, most commonly involving the anterior communicating artery, MCA bifurcation, or posterior communicating artery region, without group differences. Median ASA score was 2 in both groups. Median Fisher grade was 4 across the cohort, while Hunt–Hess (3 vs 3.5) and WFNS scores (4 vs 4) remained similar. Yasargil grades indicated overall aneurysm complexity, with grade III representing the majority of cases in both groups (64% vs 75%). (Table 1 ) Table 1 Baseline Characteristics Variable Control (n = 11) SSFS (n = 4) Total p Value Age (median) 45.0 49.5 45.0 0.743 Female (%) 73% 75% 73% 1.000 ASA (median) 2.0 2.0 2.0 0.285 Fisher (median) 4.0 4.0 4.0 0.507 Hunt-Hess (median) 3.0 3.5 3.0 0.718 WFNS (median) 4.0 4.0 4.0 0.474 AcomA (n,%) 2 (18%) 1 (25%) 3 (20%) 1.000 MCA (n,%) 8 (73%) 3 (75%) 11 (73%) 1.000 PcomA (n,%) 1 (9%) 0 (0%) 1 (7%) 1.000 Admission GCS (median) 12.0 9.5 11.0 0.400 Clinical Course and Time-to-Event Outcomes The interval from aneurysm treatment to decompressive craniectomy was similar between groups. ICU length of stay did not differ significantly (median 42 days in the control group vs 45 days in the SSFS group, p = 1.00). CSF diversion was more frequent among SSFS patients (75% vs 55%), and diversion duration showed a substantial numerical difference (median 166 days vs 2 days), although this difference did not reach statistical significance. Time-to-event patterns were also evaluated. Among patients who developed SSFS, the syndrome occurred at a median of 265 days following decompressive craniectomy (range 118–837 days). Patients without SSFS were censored at the time of cranioplasty or their last available follow-up, representing the duration during which they remained at risk for SSFS. In this group, the at-risk period ranged from 33 to 819 days, with a median of 188 days. Functional outcomes were comparable, with similar GOS scores at last follow-up. (Table 2) Descriptive Kaplan–Meier estimates illustrated the distribution of SSFS-free survival over time, although no formal survival comparison was performed due to the small number of events (Supplementary Figure S2 ) Table 2: Clinical Course Variable Control (n=11) SSFS (n=4) Total p-value Time until DC (days), median 1 0 0 0.435 GCS post-DC, median 11 10.5 11 1.000 mRS post-DC, median 4 4.5 4 0.143 ICU stay (days), median 42 45 42 1.000 CSF diversion (any), n (%) 6 (55%) 3 (75%) 9 (60%) 0.600 CSF diversion duration (days), median 2 166 17 0.106 GOS at follow-up, median 3 3 3 1.000 Cranioplasty performed, n 3 4 7 — Time-to-event or censoring (days), median 188 265 216 0.743 Craniectomy Morphometry and Radiological Findings Craniectomy size differed significantly between groups, with SSFS patients having larger defects (median 14,356 mm²) compared with non-SSFS patients (median 11,372 mm², p = 0.010). (Fig. 1 .A) Flap morphology showed marked differences: SSFS patients demonstrated prominent inward displacement (median − 31.9 mm), whereas control patients were generally at or slightly above bone level (median 0 mm, p = 0.014). (Fig. 1 .B) Midline shift exhibited a similar pattern, with SSFS patients showing significantly greater paradoxical shift (median − 13 mm) compared with non-SSFS patients (median 0 mm, p = 0.0048). Although shift presence was more common among SSFS patients (100% vs 36%), this trend did not reach statistical significance. (Fig. 1 .C) Multivariable Analysis A logistic regression model including craniectomy area and CSF diversion duration showed overall significance (p < 0.01). Craniectomy area remained the strongest independent correlate of SSFS. CSF diversion duration demonstrated a positive association but did not retain independent significance after adjustment for defect size. (Supplementary Figure S1 ) Discussion In this study, we examined risk factors associated with SSFS in a homogenous cohort of aSAH patients treated with DC. Although small, this dataset provides several insights into both the mechanisms and diagnostic challenges of SSFS in this specific population. Clinically, patients who developed SSFS demonstrated characteristic neurological decline at onset, including seizures, deterioration in consciousness, new focal deficits, or behavioral and cognitive changes. These presentations were accompanied by measurable worsening in GCS and mRS scores. Importantly, neurological improvement after cranioplasty was observed in all patients who underwent reconstruction, confirming the reversibility central to SSFS definitions. ( 1 – 3 , 5 ) A key finding of this study is the strong association between craniectomy area and SSFS development. Larger defects create greater atmospheric pressure transmission and facilitate brain sinking, consistent with prior studies across mixed etiologies. ( 6 , 7 , 14 ) In our multivariable model, craniectomy area was the only independent correlate of SSFS, underscoring its primary role in altering intracranial pressure dynamics after bone removal. CSF diversion, along with other intracranial pressure-lowering interventions, has repeatedly been implicated in the development of SSFS in the literature ( 10 , 15 – 19 ) This association reflects the role of reduced intracranial pressure in promoting flap collapse. In our cohort, SSFS patients exhibited much longer CSF diversion periods, although this did not reach statistical significance. The presence of SSFS in one patient without permanent shunting suggests that unmeasured factors may contribute to pressure disequilibrium leading to flap sinking. Unlike previous studies that combined traumatic, ischemic, and hemorrhagic etiologies, we focused specifically on aSAH. This population is physiologically distinct, as the intracranial environment evolves after aneurysm securing: hemorrhage resorption, vasospasm, delayed compliance shifts, and fluctuating CSF dynamics may influence vulnerability to SSFS in ways not present in other pathologies.( 20 ) Accordingly, we examined aSAH grading scales; however, no significant associations with SSFS were found, possibly due to small sample size. The diagnosis of SSFS may be obscured in aSAH because clinical worsening might be attributed to hydrocephalus, vasospasm, infection, or the sequelae of high-grade hemorrhage. In our cohort, two SSFS patients underwent multiple shunt revisions or valve adjustments before the syndrome was recognized, suggesting that SSFS-related deterioration may initially have been misinterpreted as shunt malfunction or other postoperative complications. This raises the possibility that the true onset of SSFS in these individuals occurred earlier than recorded, potentially leading to overestimation of time-to-event in these cases. Although most cases in the literature arise within 2–6 months after decompressive craniectomy ( 6 , 14 , 21 ), delayed presentations, occurring several months to more than a year after surgery have also been reported ( 3 , 7 , 16 ). Our median onset of 265 days (≈ 8.7 months) falls within the broader range of reported timelines, especially in the context of delayed recognition in complex postoperative courses, as seen in two patients in our cohort. Radiologically, SSFS patients displayed significant inward flap displacement and paradoxical midline shift. However, these findings are not pathognomonic. We observed a patient with a markedly sunken flap and even contralateral shift who remained entirely asymptomatic. This aligns with prior observations that radiological appearance alone is insufficient to define SSFS ( 22 , 23 ); the syndrome remains a clinical–radiological construct, and future large multicenter studies may refine meaningful cut-off thresholds for displacement or shift. Finally, although the cohort is small, its homogeneity strengthens internal validity. The rarity of DC in aSAH and the even lower frequency of SSFS make large single-center datasets unlikely; nevertheless, studies such as this contribute to cumulative understanding and may guide future multicenter collaborations. Conclusion SSFS remains a clinically relevant but often underrecognized complication after decompressive craniectomy in aSAH patients. In this homogenous cohort, larger craniectomy area emerged as the strongest correlate of SSFS, while prolonged CSF diversion showed a non-significant trend toward increased risk. The small sample size is a limitation; however, the findings illustrate how postoperative factors unique to aSAH; such as hydrocephalus, vasospasm, delayed compliance changes, and prolonged ICU course may obscure or delay SSFS recognition. Equally important, radiological sinking alone is not sufficient to diagnose SSFS, as asymptomatic flap depression was also observed. Awareness of both overdiagnosis and underdiagnosis is essential, and larger multicenter studies are needed to refine clinical and radiological thresholds and improve timely identification of SSFS. Declarations Declaration of generative AI in scientific writing During the preparation of this work, the authors used ChatGPT (OpenAI, San Francisco, CA, USA) to check grammar and improve the flow of sentences. All content was subsequently reviewed and edited by the authors, who take full responsibility for the final version of the manuscript. Availability of data and materials The data supporting the findings of this study are not publicly available but can be shared by the corresponding author upon reasonable request. Conflict of Interest: The authors declare that there are no conflicts of interest relevant to this work. x Funding: No specific funding was received for this work, the research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author Contributions: Conceptualization: Hüseyin Biçeroğlu, Taşkın Yurtseven Methodology: Hüseyin Biçeroğlu, Taşkın Yurtseven Investigation: Özde Şenol Akbulut Data curation: Özde Şenol Akbulut Formal analysis: Özde Şenol Akbulut, Bilal Bahadır Akbulut Validation: Mustafa Serdar Bölük, Hüseyin Biçeroğlu, Taşkın Yurtseven Resources: Bilal Bahadır Akbulut, Hüseyin Biçeroğlu, Taşkın Yurtseven Supervision: Hüseyin Biçeroğlu, Taşkın Yurtseven Visualization: Özde Şenol Akbulu, Mustafa Serdar Bölükt Writing – original draft: Özde Şenol Akbulut Writing – review and editing: Bilal Bahadır Akbulut, Mustafa Serdar Bölük All authors read and approved the final manuscript. References Beucler N, Dagain A. Historical Vignette Portraying the Difference Between the “Sinking Skin Flap Syndrome” and the “Syndrome of the Trephined” in Decompressive Craniectomy. World Neurosurg. 2022 June;162:11–4. Yamaura A, Makino H. 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Microneurosurgery, Volume II: Clinical Considerations, Surgery of the Intracranial Aneurysms and Results. Stuttgart: Thieme; 1984. Sveikata L, Vasung L, El Rahal A, Bartoli A, Bretzner M, Schaller K, et al. Syndrome of the trephined: clinical spectrum, risk factors, and impact of cranioplasty on neurologic recovery in a prospective cohort. Neurosurg Rev. 2021;45(2):1431–43. Han PY, Kim JH, Kang HI, Kim JS. “Syndrome of the Sinking Skin-Flap” Secondary to the Ventriculoperitoneal Shunt after Craniectomy. J Korean Neurosurg Soc. 2008;43(1):51. Romero FR, Zanini MA, Ducati LG, Gabarra RC. Sinking skin flap syndrome with delayed dysautonomic syndrome—An atypical presentation. Int J Surg Case Rep. 2013;4(11):1007–9. Zhao J, Li G, Zhang Y, Zhu X, Hou K. Sinking skin flap syndrome and paradoxical herniation secondary to lumbar drainage. Clin Neurol Neurosurg. 2015 June;133:6–10. Schwarz F, Simon M, Lawson McLean A, Kalff R, Waschke A. Assessment of Skin Flaps Above Cranial Defects Following Craniectomy: A Proposed Classification System. J Neurol Surg Part Cent Eur Neurosurg. 2020;81(01):058–63. Boccagni C, Bagnato S, Alaimo V, Galardi G. Neurologic Deterioration in Sinking Skin Flap Syndrome After Diuretic Therapy. Neurol Clin Pract [Internet]. 2021 Aug [cited 2025 Dec 4];11(4). Available from: https://www.neurology.org/doi/ 10.1212/CPJ.0000000000000859 Svedung Wettervik T, Corell A, Sunila M, Enblad P, Velle F, Lindvall P, et al. Decompressive craniectomy in aneurysmal subarachnoid hemorrhage: can favorable outcome be achieved? Acta Neurochir (Wien). 2025;167(1):68. Cholet C, André A, Law-Ye B. Sinking skin flap syndrome following decompressive craniectomy. Br J Neurosurg. 2018;32(1):73–4. Bateman EA, VanderEnde J, Sequeira K, MacKenzie HM. Postural neurologic deficits after decompressive craniectomy: A case series of sinking skin flap syndrome in traumatic brain injury. NeuroRehabilitation. 2021;49(4):663–72. Schorl M. Sinking Skin Flap Syndrome (SSFS) – Clinical Spectrum and Impact on Rehabilitation. Cent Eur Neurosurg. 2009;70(02):68–72. Additional Declarations No competing interests reported. Supplementary Files SupplementFigureS1.tiff SupplementFigureS2.tiff 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8376162","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":584210789,"identity":"8290c5c0-c24b-4114-bfc6-c06340ae4ac6","order_by":0,"name":"Özde ŞENOL AKBULUT","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIiWNgGAWjYHACAwjFDmR9ANJs7ERrYWZgKJwB0sJMipbPPFAGXsDPf3jjA4Y/Nnn8zAyMm21+bZPnAzI+fMzBrUWy4VixAWNbWrFkMwOzcW7fbcM2ZgZmyZnb8LjqYI+ZBGPD4cQNhxnYjHN7bjMCtbAx8+LTcpjH/AfDn/8gLey/LXtu2xPWcozHDBhKB0BaGIwZftxOJKhFsoetWCKxLTlxZjNjg2Fvw+3kNmbGZrx+AYXYhw9/7BL72ZsPGPz4c9t2fnvzwQ8f8WgBgwQwydjAwNgGZZAA/pCieBSMglEwCkYKAACtFErUDMA8KQAAAABJRU5ErkJggg==","orcid":"","institution":"Ege University","correspondingAuthor":true,"prefix":"","firstName":"Özde","middleName":"ŞENOL","lastName":"AKBULUT","suffix":""},{"id":584210790,"identity":"6c8c772a-c183-48e1-b558-f00592f56cd3","order_by":1,"name":"Mustafa Sedar Bölük","email":"","orcid":"","institution":"Ege University","correspondingAuthor":false,"prefix":"","firstName":"Mustafa","middleName":"Sedar","lastName":"Bölük","suffix":""},{"id":584210791,"identity":"f41d773d-292d-452b-ac82-e4db17796021","order_by":2,"name":"Bilal Bahadır Akbulut","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Bilal","middleName":"Bahadır","lastName":"Akbulut","suffix":""},{"id":584210792,"identity":"84687ac8-e5fc-4947-9a7a-a1cbba6aec0b","order_by":3,"name":"Taşkın Yurtseven","email":"","orcid":"","institution":"Ege University","correspondingAuthor":false,"prefix":"","firstName":"Taşkın","middleName":"","lastName":"Yurtseven","suffix":""},{"id":584210793,"identity":"43c3cbd3-48fb-4fe5-80c5-c4750dfe0209","order_by":4,"name":"Hüseyin Biçeroğlu","email":"","orcid":"","institution":"Ege University","correspondingAuthor":false,"prefix":"","firstName":"Hüseyin","middleName":"","lastName":"Biçeroğlu","suffix":""}],"badges":[],"createdAt":"2025-12-16 12:38:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8376162/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8376162/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101792432,"identity":"289ccfde-d1e7-40cd-914f-a781861bca39","added_by":"auto","created_at":"2026-02-03 16:12:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":106962,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of craniectomy area (A) , skin flap displacement (B), and paradoxical midline shift(C) between SSFS and non-SSFS patients.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8376162/v1/5625e6ab2f9f8a145bfb24e6.png"},{"id":103471499,"identity":"1b14f6b6-904b-4fef-b0db-377e3e2d225a","added_by":"auto","created_at":"2026-02-26 05:56:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":648754,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8376162/v1/8b52cd8f-1958-434e-9b08-31ac75638e45.pdf"},{"id":101792403,"identity":"7f715434-3b04-4207-99c4-c3f06b7d77e7","added_by":"auto","created_at":"2026-02-03 16:12:23","extension":"tiff","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":50400206,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementFigureS1.tiff","url":"https://assets-eu.researchsquare.com/files/rs-8376162/v1/6adfbe86efbb5d68dfc0f6a7.tiff"},{"id":101792501,"identity":"01c18162-3d1c-4e0e-bc29-8969feeb19e4","added_by":"auto","created_at":"2026-02-03 16:12:40","extension":"tiff","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":50400206,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementFigureS2.tiff","url":"https://assets-eu.researchsquare.com/files/rs-8376162/v1/27a8cfda7b3325fdf37e8f19.tiff"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk Factors for Sinking Skin Flap Syndrome After Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSinking Skin Flap Syndrome (SSFS) is a delayed complication following decompressive craniectomy (DC), characterized by neurologic deterioration associated with atmospheric pressure transmission through the skull defect; widely conflated with the Syndrome of Trephined, originally described by Grant and Norcross in 1939. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) The term \"sinking skin flap syndrome\" was first proposed by Yamaura et al. in 1977 after demonstrating symptom reversibility following cranioplasty (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Although uncommon, its incidence remains inconsistently reported, ranging from 7.8% to 28% according to recent reviews. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e \u003cp\u003ePathophysiologically, SSFS is thought to result from alterations in cerebrospinal fluid dynamics, impaired cerebral blood flow, and direct atmospheric pressure effects in the absence of a rigid cranial vault. This conversion of the cranium from a \u0026ldquo;closed box\u0026rdquo; to an \u0026ldquo;open box\u0026rdquo; leads to a vulnerable equilibrium, predisposing to neurological dysfunction and, in some cases, paradoxical herniation (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Most proposed SSFS risk factors such as craniectomy size, CSF diversion, brain-edema dynamics, and timing of reconstruction, have been evaluated in heterogeneous decompressive craniectomy cohorts, often combining traumatic, ischemic, and other etiologies. (\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eTo date, no study has specifically examined SSFS within a homogenous aneurysmal subarachnoid hemorrhage (aSAH) population, likely because both DC in aSAH (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) and subsequent SSFS are relatively uncommon events, making large dedicated cohorts difficult to assemble. Given the distinct intracranial dynamics associated with aSAH, including hemorrhage burden, early brain injury, fluctuating intracranial compliance, and the high incidence of hydrocephalus (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e), a focused analysis within this subgroup may provide additional insight. For this reason, we investigated SSFS exclusively in aSAH patients, evaluating both previously proposed risk factors and parameters potentially specific to the aSAH disease process.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatement of Ethics\u003c/h2\u003e \u003cp\u003e This study was conducted in accordance with the principles outlined in the Declaration of Helsinki. Ethical approval was obtained from the local ethics committee (25-12T/70). Informed consent was obtained for every patient prior to the surgery.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStudy Population and Clinical Variables\u003c/h3\u003e\n\u003cp\u003ePatients who underwent decompressive hemicraniectomy for aneurysmal subarachnoid hemorrhage (aSAH) between 2014 and 2024 were retrospectively evaluated. Only standard hemicraniectomies were included. Atypical craniectomy types, extradural aneurysms, and patients who survived less than one month after aneurysm treatment were excluded as SSFS has been consistently reported to develop at least several weeks after decompressive craniectomy, and these patients would not have provided adequate time-to-event observation. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eDemographic and clinical variables included age, sex, ASA score, admission Glasgow Coma Scale (GCS), and pre-DC modified Rankin Scale (mRS). aSAH severity was characterized using established grading systems: Hunt\u0026ndash;Hess and WFNS scores to describe initial clinical severity (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), Fisher grade to quantify hemorrhage load, reflecting both its known association with vasospasm risk and its impact on intracranial compliance dynamics (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), and Yasargil aneurysm grade to capture aneurysm rupture complexity (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Aneurysm location and treatment modality (microsurgical clipping or endovascular treatment) were also recorded.\u003c/p\u003e \u003cp\u003ePost-decompressive course variables included Glasgow Outcome Scale (GOS), mRS at last follow-up, ICU length of stay, and time-to-event data regarding SSFS development. SSFS onset was treated as the event of interest. For patients who underwent cranioplasty or had no SSFS during follow-up, the interval from decompressive craniectomy to the date of cranioplasty or last available clinical/radiological assessment was recorded as censoring time, as these patients remained at risk for SSFS until that point.\u003c/p\u003e \u003cp\u003eCerebrospinal fluid (CSF) diversion was documented by presence of lumbar drainage, external ventricular drainage, or permanent shunting, and the total duration of diversion was calculated as the cumulative number of days during which any diversion system was in place.\u003c/p\u003e\n\u003ch3\u003eRadiological Assessment\u003c/h3\u003e\n\u003cp\u003eFor radiological analysis, craniectomy surface area was measured using Meshmixer (Autodesk Inc., San Rafael, CA, USA; version 3.5). Preoperative and postoperative CT scans were converted into overlapping 3D models, and the craniectomy region was manually isolated to obtain surface area values. The most recent CT prior to cranioplasty, or the latest available follow-up CT in patients without cranioplasty, was evaluated for skin flap level (sunken, isolevel, or bulging), degree of displacement of the skin flap relative to the original bone margin, and presence and magnitude of midline shift.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eContinuous variables (e.g., age, ICU stay, craniectomy area, CSF diversion duration, radiological measurements) and ordinal variables (Fisher grade, Hunt\u0026ndash;Hess grade, WFNS grade, Yasargil aneurysm grade) were compared between patients with and without SSFS using the Mann\u0026ndash;Whitney U test, given the small sample size and non-normal distribution. Categorical variables, such as presence of comorbidity, CSF diversion, or radiological midline shift, were analyzed using Fisher\u0026rsquo;s exact test.\u003c/p\u003e \u003cp\u003eBecause SSFS represents a time-dependent outcome, a time-to-event framework was applied to describe the interval between decompressive craniectomy and either SSFS onset (event) or censoring. SSFS onset was treated as the event of interest. For patients without SSFS, the interval from craniectomy to cranioplasty or last available follow-up was recorded as censoring time. Kaplan\u0026ndash;Meier estimates were used descriptively to illustrate SSFS-free survival over time.\u003c/p\u003e \u003cp\u003eA multivariable logistic regression model was constructed to evaluate independent associations with SSFS, including craniectomy area and CSF diversion duration as covariates. Odds ratios, 95% confidence intervals, and model significance were reported. A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 28 patients were screened, and 15 met eligibility criteria for the final analysis. All aneurysms in the study cohort were treated with microsurgical clipping; no patient underwent endovascular treatment. Four patients (27%) developed sinking flap syndrome (SSFS), while eleven patients constituted the control group.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eBaseline Characteristics\u003c/h2\u003e \u003cp\u003eSystemic and hemorrhage-severity indicators did not differ significantly between groups. Median age was comparable (45 years in the control group vs 49.5 years in the SSFS group), as was sex distribution. Aneurysm locations were typical for high-grade aSAH, most commonly involving the anterior communicating artery, MCA bifurcation, or posterior communicating artery region, without group differences. Median ASA score was 2 in both groups. Median Fisher grade was 4 across the cohort, while Hunt\u0026ndash;Hess (3 vs 3.5) and WFNS scores (4 vs 4) remained similar. Yasargil grades indicated overall aneurysm complexity, with grade III representing the majority of cases in both groups (64% vs 75%). (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\u003eBaseline Characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\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\u003eControl (n\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSSFS (n\u0026thinsp;=\u0026thinsp;4)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\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 (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e45.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.743\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\u003e73%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e73%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.285\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFisher (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.507\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHunt-Hess (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.718\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWFNS (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.474\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAcomA (n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (18%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 (20%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMCA (n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (73%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (75%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11 (73%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePcomA (n,%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1 (7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdmission GCS (median)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.400\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\n\u003ch3\u003eClinical Course and Time-to-Event Outcomes\u003c/h3\u003e\n\u003cp\u003eThe interval from aneurysm treatment to decompressive craniectomy was similar between groups. ICU length of stay did not differ significantly (median 42 days in the control group vs 45 days in the SSFS group, p\u0026thinsp;=\u0026thinsp;1.00). CSF diversion was more frequent among SSFS patients (75% vs 55%), and diversion duration showed a substantial numerical difference (median 166 days vs 2 days), although this difference did not reach statistical significance.\u003c/p\u003e \u003cp\u003eTime-to-event patterns were also evaluated. Among patients who developed SSFS, the syndrome occurred at a median of 265 days following decompressive craniectomy (range 118\u0026ndash;837 days). Patients without SSFS were censored at the time of cranioplasty or their last available follow-up, representing the duration during which they remained at risk for SSFS. In this group, the at-risk period ranged from 33 to 819 days, with a median of 188 days. Functional outcomes were comparable, with similar GOS scores at last follow-up. (Table\u0026nbsp;2) Descriptive Kaplan\u0026ndash;Meier estimates illustrated the distribution of SSFS-free survival over time, although no formal survival comparison was performed due to the small number of events (Supplementary Figure \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eTable 2: Clinical Course\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"604\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003eControl (n=11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eSSFS (n=4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eTime until DC (days), median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e0.435\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eGCS post-DC, median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e10.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003emRS post-DC, median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e0.143\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eICU stay (days), median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eCSF diversion (any), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e6 (55%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e3 (75%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e9 (60%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e0.600\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eCSF diversion duration (days), median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e166\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e0.106\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eGOS at follow-up, median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eCranioplasty performed, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003eTime-to-event or censoring (days), median\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 116px;\"\u003e\n \u003cp\u003e188\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e265\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 92px;\"\u003e\n \u003cp\u003e216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 90px;\"\u003e\n \u003cp\u003e0.743\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\u003c/br\u003e\n\u003ch3\u003eCraniectomy Morphometry and Radiological Findings\u003c/h3\u003e\n\u003cp\u003eCraniectomy size differed significantly between groups, with SSFS patients having larger defects (median 14,356 mm\u0026sup2;) compared with non-SSFS patients (median 11,372 mm\u0026sup2;, p\u0026thinsp;=\u0026thinsp;0.010). (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.A)\u003c/p\u003e \u003cp\u003eFlap morphology showed marked differences: SSFS patients demonstrated prominent inward displacement (median \u0026minus;\u0026thinsp;31.9 mm), whereas control patients were generally at or slightly above bone level (median 0 mm, p\u0026thinsp;=\u0026thinsp;0.014). (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.B)\u003c/p\u003e \u003cp\u003eMidline shift exhibited a similar pattern, with SSFS patients showing significantly greater paradoxical shift (median \u0026minus;\u0026thinsp;13 mm) compared with non-SSFS patients (median 0 mm, p\u0026thinsp;=\u0026thinsp;0.0048). Although shift presence was more common among SSFS patients (100% vs 36%), this trend did not reach statistical significance. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.C)\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eMultivariable Analysis\u003c/h2\u003e \u003cp\u003eA logistic regression model including craniectomy area and CSF diversion duration showed overall significance (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Craniectomy area remained the strongest independent correlate of SSFS. CSF diversion duration demonstrated a positive association but did not retain independent significance after adjustment for defect size. (Supplementary Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e)\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we examined risk factors associated with SSFS in a homogenous cohort of aSAH patients treated with DC. Although small, this dataset provides several insights into both the mechanisms and diagnostic challenges of SSFS in this specific population.\u003c/p\u003e \u003cp\u003eClinically, patients who developed SSFS demonstrated characteristic neurological decline at onset, including seizures, deterioration in consciousness, new focal deficits, or behavioral and cognitive changes. These presentations were accompanied by measurable worsening in GCS and mRS scores. Importantly, neurological improvement after cranioplasty was observed in all patients who underwent reconstruction, confirming the reversibility central to SSFS definitions. (\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eA key finding of this study is the strong association between craniectomy area and SSFS development. Larger defects create greater atmospheric pressure transmission and facilitate brain sinking, consistent with prior studies across mixed etiologies. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) In our multivariable model, craniectomy area was the only independent correlate of SSFS, underscoring its primary role in altering intracranial pressure dynamics after bone removal.\u003c/p\u003e \u003cp\u003eCSF diversion, along with other intracranial pressure-lowering interventions, has repeatedly been implicated in the development of SSFS in the literature (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR16 CR17 CR18\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) This association reflects the role of reduced intracranial pressure in promoting flap collapse. In our cohort, SSFS patients exhibited much longer CSF diversion periods, although this did not reach statistical significance. The presence of SSFS in one patient without permanent shunting suggests that unmeasured factors may contribute to pressure disequilibrium leading to flap sinking.\u003c/p\u003e \u003cp\u003eUnlike previous studies that combined traumatic, ischemic, and hemorrhagic etiologies, we focused specifically on aSAH. This population is physiologically distinct, as the intracranial environment evolves after aneurysm securing: hemorrhage resorption, vasospasm, delayed compliance shifts, and fluctuating CSF dynamics may influence vulnerability to SSFS in ways not present in other pathologies.(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) Accordingly, we examined aSAH grading scales; however, no significant associations with SSFS were found, possibly due to small sample size.\u003c/p\u003e \u003cp\u003eThe diagnosis of SSFS may be obscured in aSAH because clinical worsening might be attributed to hydrocephalus, vasospasm, infection, or the sequelae of high-grade hemorrhage. In our cohort, two SSFS patients underwent multiple shunt revisions or valve adjustments before the syndrome was recognized, suggesting that SSFS-related deterioration may initially have been misinterpreted as shunt malfunction or other postoperative complications. This raises the possibility that the true onset of SSFS in these individuals occurred earlier than recorded, potentially leading to overestimation of time-to-event in these cases.\u003c/p\u003e \u003cp\u003eAlthough most cases in the literature arise within 2\u0026ndash;6 months after decompressive craniectomy (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e), delayed presentations, occurring several months to more than a year after surgery have also been reported (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Our median onset of 265 days (\u0026asymp;\u0026thinsp;8.7 months) falls within the broader range of reported timelines, especially in the context of delayed recognition in complex postoperative courses, as seen in two patients in our cohort.\u003c/p\u003e \u003cp\u003eRadiologically, SSFS patients displayed significant inward flap displacement and paradoxical midline shift. However, these findings are not pathognomonic. We observed a patient with a markedly sunken flap and even contralateral shift who remained entirely asymptomatic. This aligns with prior observations that radiological appearance alone is insufficient to define SSFS (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e); the syndrome remains a clinical\u0026ndash;radiological construct, and future large multicenter studies may refine meaningful cut-off thresholds for displacement or shift.\u003c/p\u003e \u003cp\u003eFinally, although the cohort is small, its homogeneity strengthens internal validity. The rarity of DC in aSAH and the even lower frequency of SSFS make large single-center datasets unlikely; nevertheless, studies such as this contribute to cumulative understanding and may guide future multicenter collaborations.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eSSFS remains a clinically relevant but often underrecognized complication after decompressive craniectomy in aSAH patients. In this homogenous cohort, larger craniectomy area emerged as the strongest correlate of SSFS, while prolonged CSF diversion showed a non-significant trend toward increased risk. The small sample size is a limitation; however, the findings illustrate how postoperative factors unique to aSAH; such as hydrocephalus, vasospasm, delayed compliance changes, and prolonged ICU course may obscure or delay SSFS recognition. Equally important, radiological sinking alone is not sufficient to diagnose SSFS, as asymptomatic flap depression was also observed. Awareness of both overdiagnosis and underdiagnosis is essential, and larger multicenter studies are needed to refine clinical and radiological thresholds and improve timely identification of SSFS.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of generative AI in scientific writing\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring the preparation of this work, the authors used ChatGPT \u0026nbsp;(OpenAI, San Francisco, CA, USA) to check grammar and improve the flow of sentences. All content was subsequently reviewed and edited by the authors, who take full responsibility for the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data supporting the findings of this study are not publicly available but can be shared by the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest relevant to this work. x\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo specific funding was received for this work, the research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: H\u0026uuml;seyin Bi\u0026ccedil;eroğlu, Taşkın Yurtseven\u003c/p\u003e\n\u003cp\u003eMethodology: H\u0026uuml;seyin Bi\u0026ccedil;eroğlu, Taşkın Yurtseven\u003c/p\u003e\n\u003cp\u003eInvestigation: \u0026Ouml;zde Şenol Akbulut\u003c/p\u003e\n\u003cp\u003eData curation: \u0026Ouml;zde Şenol Akbulut\u003c/p\u003e\n\u003cp\u003eFormal analysis: \u0026Ouml;zde Şenol Akbulut, Bilal Bahadır Akbulut\u003c/p\u003e\n\u003cp\u003eValidation: Mustafa Serdar B\u0026ouml;l\u0026uuml;k, H\u0026uuml;seyin Bi\u0026ccedil;eroğlu, Taşkın Yurtseven\u003c/p\u003e\n\u003cp\u003eResources: Bilal Bahadır Akbulut, H\u0026uuml;seyin Bi\u0026ccedil;eroğlu, Taşkın Yurtseven\u003c/p\u003e\n\u003cp\u003eSupervision: H\u0026uuml;seyin Bi\u0026ccedil;eroğlu, Taşkın Yurtseven\u003c/p\u003e\n\u003cp\u003eVisualization: \u0026Ouml;zde Şenol Akbulu, Mustafa Serdar B\u0026ouml;l\u0026uuml;kt\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; original draft: \u0026Ouml;zde Şenol Akbulut\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; review and editing: Bilal Bahadır Akbulut, Mustafa Serdar B\u0026ouml;l\u0026uuml;k\u003c/p\u003e\n\u003cp\u003eAll authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBeucler N, Dagain A. 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Neurosurg Rev. 2021;45(2):1431\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan PY, Kim JH, Kang HI, Kim JS. \u0026ldquo;Syndrome of the Sinking Skin-Flap\u0026rdquo; Secondary to the Ventriculoperitoneal Shunt after Craniectomy. J Korean Neurosurg Soc. 2008;43(1):51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRomero FR, Zanini MA, Ducati LG, Gabarra RC. Sinking skin flap syndrome with delayed dysautonomic syndrome\u0026mdash;An atypical presentation. Int J Surg Case Rep. 2013;4(11):1007\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao J, Li G, Zhang Y, Zhu X, Hou K. Sinking skin flap syndrome and paradoxical herniation secondary to lumbar drainage. Clin Neurol Neurosurg. 2015 June;133:6\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchwarz F, Simon M, Lawson McLean A, Kalff R, Waschke A. Assessment of Skin Flaps Above Cranial Defects Following Craniectomy: A Proposed Classification System. J Neurol Surg Part Cent Eur Neurosurg. 2020;81(01):058\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoccagni C, Bagnato S, Alaimo V, Galardi G. Neurologic Deterioration in Sinking Skin Flap Syndrome After Diuretic Therapy. Neurol Clin Pract [Internet]. 2021 Aug [cited 2025 Dec 4];11(4). Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.neurology.org/doi/\u003c/span\u003e\u003cspan address=\"https://www.neurology.org/doi/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1212/CPJ.0000000000000859\u003c/span\u003e\u003cspan address=\"10.1212/CPJ.0000000000000859\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSvedung Wettervik T, Corell A, Sunila M, Enblad P, Velle F, Lindvall P, et al. Decompressive craniectomy in aneurysmal subarachnoid hemorrhage: can favorable outcome be achieved? Acta Neurochir (Wien). 2025;167(1):68.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCholet C, Andr\u0026eacute; A, Law-Ye B. Sinking skin flap syndrome following decompressive craniectomy. Br J Neurosurg. 2018;32(1):73\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBateman EA, VanderEnde J, Sequeira K, MacKenzie HM. Postural neurologic deficits after decompressive craniectomy: A case series of sinking skin flap syndrome in traumatic brain injury. NeuroRehabilitation. 2021;49(4):663\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchorl M. Sinking Skin Flap Syndrome (SSFS) \u0026ndash; Clinical Spectrum and Impact on Rehabilitation. Cent Eur Neurosurg. 2009;70(02):68\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e\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":"Sinking Skin Flap Syndrome, Decompressive Craniectomy, Aneurysmal Subarachnoid Hemorrhage, Cerebrospinal Fluid Diversion, Cranioplasty, Cerebrospinal Fluid Drainage","lastPublishedDoi":"10.21203/rs.3.rs-8376162/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8376162/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eTo evaluate clinical, radiological, and procedural risk factors for sinking skin flap syndrome (SSFS) following decompressive craniectomy (DC) in a homogenous cohort of aneurysmal subarachnoid hemorrhage (aSAH) patients.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003ePatients who underwent DC for aSAH between 2014\u0026ndash;2024 were retrospectively reviewed. Demographic variables, hemorrhage severity scores, CSF diversion characteristics, craniectomy morphometry, and radiological measurements were compared between patients with and without SSFS. Time-to-event analysis was used to characterize SSFS onset. Mann\u0026ndash;Whitney U and Fisher\u0026rsquo;s exact tests were applied for group comparisons. A multivariable logistic regression model was constructed including craniectomy area and CSF diversion duration.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eFifteen patients met inclusion criteria; four (27%) developed SSFS. Baseline demographics, hemorrhage grades, and aneurysm features were comparable between groups. SSFS patients had significantly larger craniectomy areas and exhibited greater flap sinking and paradoxical midline shift. CSF diversion duration was longer in SSFS patients but not statistically significant. SSFS occurred at a median of 265 days after DC, and all affected patients showed neurological improvement following cranioplasty. Non-SSFS patients had adequate at-risk follow-up without events.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eIn aSAH patients, larger craniectomy area is a strong predictor of SSFS, while prolonged CSF diversion demonstrates a non-significant trend toward increased risk. Diagnostic delays in the complex aSAH postoperative course may mask true onset. Radiological sinking alone is insufficient for diagnosis, as asymptomatic flap depression also occurred. Improved awareness is required to avoid both under- and overdiagnosis, and larger multicenter studies are needed to define clinical and radiological thresholds for SSFS.\u003c/p\u003e","manuscriptTitle":"Risk Factors for Sinking Skin Flap Syndrome After Decompressive Craniectomy in Aneurysmal Subarachnoid Hemorrhage","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-03 16:11:08","doi":"10.21203/rs.3.rs-8376162/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":"71216b16-6e9d-4527-9d43-a8188f05f51e","owner":[],"postedDate":"February 3rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-26T05:55:52+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-03 16:11:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8376162","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8376162","identity":"rs-8376162","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}