Correlation Between Membranectomy in Chronic Subdural Hematoma and Postoperative Seizures: A Retrospective Institution-Based Analysis at a Tertiary Care Center in India

Abstract

Background

Chronic subdural hematoma (SDH) is a common neurosurgical condition, particularly in the elderly, characterized by blood accumulation between the dura and arachnoid membranes. While burr-hole drainage remains the standard treatment, some surgeons perform membranectomy—surgical removal of the hematoma's encapsulating membranes—believing it reduces recurrence and facilitates brain re-expansion. However, its role in influencing postoperative complications, especially seizures, remains controversial.

Aims

This study aimed to assess the correlation between membranectomy and the incidence of postoperative seizures in patients surgically treated for chronic SDH, and to compare these findings with existing literature to guide clinical decision-making

Settings and Design

Hospital-based retrospective analytical study.

Methods

A retrospective analytical study was conducted at R.G. Kar Medical College, Kolkata, including 56 patients treated surgically for chronic SDH between November 2024 and April 2025. Data on demographics, comorbidities, radiological characteristics, surgical procedures (with or without membranectomy), and postoperative outcomes were collected. All patients received prophylactic antiseizure medications. The incidence of postoperative seizures was analyzed, and statistical significance was tested using chi-square analysis with odds ratios.

Results

Of the 56 patients, 22 underwent membranectomy with their primary procedure, while 34 did not. Overall, 14.3% developed postoperative seizures despite prophylaxis. The seizure rate was 27.3% in the membranectomy group, compared with 5.9% in the non-membranectomy group. The odds ratio for developing seizures with membranectomy was 6 (95% confidence interval: 1.09–33.2; p = 0.0025), indicating a statistically significant association.

Conclusion

This institutional study demonstrates that membranectomy in chronic SDH surgery is associated with a significantly higher risk of postoperative seizures, aligning with some previous reports. Given the increased morbidity associated with seizures, routine membranectomy should be reconsidered, emphasizing burr-hole drainage as the primary approach unless otherwise clinically indicated. Further large-scale studies are warranted to validate these findings and optimize surgical protocols for chronic SDH.

Keywords

chronic subdural hematoma - seizure - membranectomy

Key Messages

Membranectomy in chronic SDH surgery is one of the attributable factors to seizure, hence better to avoid it routinely.

Introduction

Chronic subdural hematoma (SDF) is a prevalent neurological condition, particularly among the elderly, characterized by the accumulation of blood between the dura mater and the arachnoid membrane.[1] Surgical intervention remains the primary treatment modality, with options ranging from burr-hole drainage to craniotomy; however, there is also scope for medical management, like low-dose steroids or tranexamic acid,[2] and endovascular management as well.[3] In certain cases, membranectomy—the surgical removal of the hematoma's encapsulating membranes—is performed to facilitate hematoma evacuation and reduce recurrence rates.[4]

Postoperative seizure is a recognized complication following chronic SDH (CSDH), with reported incidences varying widely across studies. The etiology of these seizures is multifactorial, encompassing factors such as cortical irritation, residual hematoma, and surgical technique. Several studies have shown that factors such as low Glasgow Coma Scale (GCS) on admission,[5] previous history of stroke, recurrent CSDH,[6] large depressed brain volume,[7] trabecular hematoma, and known cardiac disease serve as independent risk factors for seizure in CSDH.[8] Prophylactic antiseizure medications are routinely used in the treatment protocol of CSDH.[9] Prior retrospective studies have shown membranectomy as a potential risk factor for postoperative seizure in CSDH,[10] but confounders like radiological type of CSDH or cortical indentations were inconsistently linked with postoperative seizure risk. In membranectomy cohorts, these imaging features are often the very reason for performing inner membrane dissection, yet seizure outcomes are rarely stratified by them. Also, in the Indian setting, there is no prior literature suggesting membranectomy as a risk factor for postoperative seizure in CSDH, although membranectomy is being practiced in CSDH to reduce recurrence in India.

This study aims to assess the correlation between membranectomy and postoperative seizures in patients undergoing surgical treatment for CSDH. By analyzing our institutional data and comparing findings with existing literature, we seek to elucidate the potential impact of membranectomy on seizure risk and inform surgical decision-making.

Objectives

• To evaluate the incidence of postoperative seizures in patients undergoing surgery for CSDH.

• To determine the correlation between membranectomy and postoperative seizures in CSDH.

Methods

A retrospective analytical study was conducted among patients who had undergone surgery for CSDH in R. G. Kar Medical College, Kolkata from November 2024 to April 2025 after taking permission from the institutional scientific and ethical committee. As this is a retrospective study, consents were not obtained from the patients for data collection. Information regarding age, sex, preoperative GCS, history of alcoholism and anticoagulant intake, past history of stroke, comorbidities, radiological type of CSDH (Nakaguchi Classification),[11] and midline shift on CT scan ([Fig. 1]) was collected from medical notes. Patients with previous history of seizure, on anti-seizure medications, previous history of brain surgery, and age <18 years were excluded from the study. Those patients who sustained intra-op brain parenchymal injuries were also excluded from the study. Surgical notes mentioning the procedure and whether membranectomy was done or not and postoperative notes mentioning about seizure episodes and how they were managed were also collected. Postoperative seizure was defined as any episode of seizure that occurred within 7 days of surgery. Patients usually were discharged 7 days after surgery, so all episodes were reported by medical personnel and were documented in clinical notes. Data of a total of 56 patients were collected. They underwent several procedures like single-burr hole craniotomy ([Fig. 2]), double-burr hole craniotomy, mini-craniotomy (3 cm in diameter), mini-craniotomy with membranectomy ([Fig. 3]), and decompressive craniectomy (12*10 cm in diameter) with membranectomy ([Fig. 4]). These surgeries were done by different surgeons and they were followed up in the postoperative period. Prophylactic antiseizure medications (1 g Inj. levetiracetam stat dose) were given to every single patient during the induction phase of anesthesia prior to surgery, and they were kept under antiepileptic coverage (Inj./tab levetiracetam 500*bd) during their hospital stay as a prophylactic measure. However, if they developed a seizure or status epilepticus despite prophylaxis, then they were treated accordingly and it was recorded in their medical notes.

Fig. 1 NCCT brain showing left side chronic SDH with >1 cm midline shift toward right. (Image produced after taking proper consent from the patient.) NCCT, noncontrast computed tomography; SDH, subdural hematoma.

Fig. 2 Intraoperative picture of left side burr hole evacuation of chronic SDH. (Image produced after taking proper consent from the patient.) SDH, subdural hematoma.

Fig. 3 Intraoperative picture of left parietal mini craniotomy showing underlying brain free of inner membrane after evacuation of chronic SDH. (Image produced after taking proper consent from the patient.) SDH, subdural hematoma.

Fig. 4 Intraoperative picture of right frontoparietal decompressive craniotomy with underlying thick membrane inside in a case of chronic SDH. (Image produced after taking proper consent from the patient.) SDH, subdural hematoma.

Finally, data were statistically analyzed using Microsoft Excel and SPSS 2.0. The incidence of postoperative seizures was calculated for both membranectomy and non-membranectomy groups. A chi-square test was employed to assess the statistical significance of the association between membranectomy and postoperative seizures, as well as odds ratios (ORs) were calculated. A p-value of <0.05 was considered statistically significant.

Results

Out of the 56 patients, a total of 22 patients had membranectomy with their primary procedure and the remaining 34 underwent either burr hole craniotomy or mini-craniotomy only. Patients were selected randomly for membranectomy by the operating surgeon. As shown in [Table 1], there is no statistical difference in distribution of patients in membranectomy and non-membranectomy groups according to their primary characteristics like age, sex, comorbidities, past history of stroke, history of alcohol intake, history of anticoagulant intake, preop GCS, radiological classification, and midline shift on computed tomography (CT) scan.

Table 1 Basic characteristics and distribution of patients according to independent variables in membranectomy and non-membranectomy groups (n = 56)

Variables	Membranectomy (n = 22)	Non-membranectomy (n = 34)	p-Value
Age, mean ± SD (years)	59.6 ± 12.1	61.4 ± 10.8	0.52
Male sex, n (%)	15 (68.2)	23 (67.6)	0.96
H/O head trauma, n (%)	12 (54.5)	18 (52.9)	0.97
Presenting complaint
Headache only, n (%)	12 (54.5)	16 (47.1)	0.52
Headache and vomiting, n (%)	8 (36.4)	11 (32.4)
Headache and hemiparesis, n (%)	2 (9.1)	7 (20.5)
Duration of symptom, mean ± SD (days)	20.7 ± 8.5	17.3 ± 10.6	0.19
Alcohol use, n (%)	14 (63.6)	20 (58.8)	0.72
Anticoagulant use, n (%)	10 (45.4)	17 (50.0)	0.73
Hypertension, n (%)	11 (50.0)	15 (44.1)	0.66
Diabetes, n (%)	7 (31.8)	9 (26.5)	0.67
Previous stroke, n (%)	2 (9.1)	4 (11.8)	0.77
Preop GCS
15, n (%)	9 (40.9)	16 (47.1)	0.39
14, n (%)	12 (54.5)	14 (41.2)
13, n (%)	1 (4.6)	4 (11.8)
Radiological type[11]
Homogeneous	4 (18.1%)	11 (32.4%)	0.12
Laminar	4 (18.1%)	9 (26.5%)
Separated	6 (27.4%)	8 (23.5%)
Trabecular	8 (36.4%)	6 (17.6%)
Midline shift in CT scan
< 0.5 cm	6 (27.3%)	12 (35.3%)	0.95
0.5–1 cm	12 (54.5%)	16 (47.1%)
> 1 cm	4 (18.2%)	6 (17.6%)

Abbreviations: CT, computed tomography; GCS, Glasgow Coma Scale; SD, standard deviation.

A total of 8 (14.3%) patients out of the 56 developed seizures in the postoperative period despite prophylactic antiseizure medications and were managed accordingly. All of them developed generalized tonic-clonic seizure, two patients had seizure on post-op day 1, and six had them on post-op day 0. In the membranectomy and non-mebranectomy groups, 6 (27.3%) and 2 (5.9%) had seizure episodes. On univariate analysis ([Table 2]), membranectomy was significantly associated with higher odds of postoperative seizure (OR 6.00, 95% confidence interval [CI]: 1.09–33.2, p = 0.0025). Other factors, including age, sex, alcohol use, anticoagulant use, hypertension, diabetes, midline shift, and trabecular subtype were not significantly associated. Primarily, levetiracetam was used as a prophylactic antiseizure medication, but in those eight patients who developed seizure, phenytoin was used along with levetiracetam for management. Four out of those eight patients had status epilepticus and they had to be kept sedated for 1 day along with antiseizure medication. Radiological resorption was seen in 50 out of 56 patients of CSDH in follow-up CT scan.

Table 2 Distribution of patients according to different variables in seizure and non-seizure groups (n = 56)

Variable	Seizure (n = 8)	No seizure (n = 48)	OR (95% CI)	p-Value
Age, mean ± SD (years)	61.1 ± 9.8	60.6 ± 11.7	–	0.91
Male sex, n (%)	5 (62.5)	33 (68.8)	0.76 (0.15–3.73)	0.72
Alcohol use, n (%)	5 (62.5)	29 (60.4)	1.09 (0.23–5.14)	0.91
Anticoagulant use, n (%)	4 (50.0)	23 (47.9)	1.09 (0.24–4.83)	0.90
Previous stroke, n (%)	2 (25.0)	4 (8.3)	3.67 (0.53–25.2)	0.18
Trabecular hematoma, n (%)	2 (25.0)	12 (25.0)	1.00 (0.18–5.63)	0.93
Midline shift >1 cm, n (%)	3 (37.5)	7 (14.6)	3.40 (0.64–18.0)	0.15
Membranectomy, n (%)	6 (75.0)	16 (33.3)	6.00 (1.09–33.2)	0.0025

Abbreviations: CI, computed tomography; OR, odds ratio; SD, standard deviation.

Discussion

Postoperative seizures remain a significant complication following surgical management of CSDH, with reported incidence ranging from 2 to 15% in the literature.[10] [11] [12] [13] [14] [15] This condition following surgery increases morbidity and affects patient outcome. Membranectomy is performed by some surgeons in the belief that it would not only prevent recurrence but also help in optimal brain expansion following surgery. But it carries a significant risk of inadvertent cortical injury. Studies have shown[10] membranectomy as one of the risk factors for postoperative seizure in CSDH. Although the mechanism is still unclear, it could be due to cortical injury or arachnoid injury during membranectomy, or direct contact of blood products to the cerebral cortex following membranectomy. There are also other risk factors for seizure in CSDH, like large volume, significant brain depression, trabecular variety, previous history of stroke, associated cardiac comorbidities, alcoholism, etc. ([Table 3]).

Table 3 Various studies showing risk factors of seizure in chronic SDH

Study (year)	Cohort size	Seizure rate	Membranectomy risk	Other key risks
Goertz et al (2019)[10]	101	13.9%	Yes (OR 3.9)	Midline shift
Kotwica and Brzeziński (1988)[12]	161	14.9%	N/A	Low GCS, cognitive impairment
Lee et al (2017)[13]	220	2.3%	N/A	Low mean GCS
Bender et al (2022)[14]	211	9%	No	Craniotomy, left side, drain misplacement
Ranawaka et al (2025)[15]	580	1.3–12.1%	N/A	Surgical modality + MMAe

Abbreviations: GCS, Glasgow Coma Scale; OR, odds ratio; SDH, subdural hematoma.

Meta-analysis[16] done on 250 studies showcased that burr-hole evacuation of hematoma with drain was quite effective as far as morbidity and recurrence are concerned; however, decompressive craniotomy was effective in recurrent cases, although it had more morbidity compared with other procedures.

Our study has shown that membranectomy in CSDH is associated with sixfold increased occurrence of seizure (OR: 6.00, 95% CI: 1.09–33.2, p = 0.0025), which is also statistically significant. Other factors like previous history of stroke, mass effect, and trabecular variety of hematoma have not shown a statistically significant association with postoperative seizure in our study. Burr-hole evacuation or procedures like larger decompression are required as per diagnosis, but membranectomy in all procedures has larger risk factors, such as seizure.

However, as this is a retrospective study with a small sample size, it has multiple limitations and results cannot be generalized. EEG was not routinely done in all postoperative patients, so subclinical events remained undiagnosed and the follow-up period was only for 7 days, so late postoperative seizures were not reported. Also, metabolic factors like hyponatremia were not routinely evaluated; hence, membranectomy cannot be solely attributed to every single seizure episode.

The higher rate of occurrence of seizure following membranectomy in CSDH that has been observed also aligns with previous studies, but other possible risk factors like previous history of stroke, trabecular variety of hematoma, and preoperative significant mass effect have not shown a statistically relevant association, which is unique in this study.

Conclusion

CSDH is one of the prevalent neurological conditions affecting the elderly population. It can be managed either conservatively or with surgery. Burr hole evacuation of hematoma remains the surgery of choice; however, in some cases larger craniotomy is indicated for management of recurrence. Many surgeons believe that membranectomy prevents recurrence, but it is associated with a higher risk, which leads to significant morbidity and unfavorable patient outcomes.

Conflict of Interest

None declared.

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Publication History

Article published online:
13 November 2025