Post-operative seizures after burr hole evacuation of chronic subdural hematomas: is prophylactic anti-epileptic medication needed?
There are limited data with regards to the associated risk of post-operative seizures in patients with surgically treated chronic subdural hematomas (CSDHs). The use of anti-epileptic drugs (AEDs) is associated with significant side effects.
A retrospective chart review was performed on patients operated via burr hole for CSDH in our institution from 2004 to 2013. Post-operative seizures at 1-year follow-up were identified. Demographic data, medical history, and imaging characteristics were recorded.
A total of 220 patients were included in the study. Post-operative seizures occurred in 2.3%. The mean time of onset of seizures was 8.4 days. No difference in age and gender between seizing and non-seizing groups was identified p > 0.05. Mean midline shift was 4.6 mm in seizing group vs. 4.2 mm in non-seizing group, p > 0.05. Mean thickness was 14.6 mm in patients without post-operative seizures and 18.4 mm in patients with post-operative seizures, p > 0.05. There was no significant difference in post-operative seizure incidence related to the side or location of the CSDHs.
The incidence of post-operative seizures in patients with CSDH evacuated via burr holes was low. Prophylactic AEDs should not be routinely administered if no other risk factor for seizure exists. Demographic and clinical factors did not appear to influence post-operative seizures.
KeywordsChronic Subdural Hematoma Seizures Prophylaxis Post-operative
Chronic subdural hematomas (CSDHs) are one of the most common entities encountered by neurosurgeons worldwide. CSDHs often occur as sequelae of minor head trauma, or a traumatic head injury that causes an acute subdural hematoma that is unrecognized or treated non-surgically with later conversion into a CSDH.
The incidence of CSDHs increases with age, with a recent estimated incidence of 58/100,000/year for patients between 70 and 79 years old and 127.1/100,000/year in those over 80 years old [8, 9]. Treatment of symptomatic CSDHs remains standard, consisting of drainage via burr holes or craniotomy with or without a subdural drainage system . However, controversy exists in the management of seizure prophylaxis and prevention of post-operative seizures following evacuation. Studies have shown that the incidence of post-operative seizures in patients with CSDHs range from 1 to 23.4% [5, 7].
In the management of neurosurgical patients, the prevention of seizures is important due to their negative impact on quality of life . The onset of seizures in patients with CSDHs has been shown to greatly increase the incidence of subsequent seizures/epilepsy and the chance of secondary harm [11, 16]. Nonetheless, the administration of anti-epileptic drugs (AEDs) in the peri-operative period in patients with brain injury without a history of seizures has not been shown to prevent epileptogenesis [3, 4, 14, 15, 17].
AEDs should not be disregarded as innocuous, especially in the elderly, who are usually predisposed to CSDHs. Differing metabolic profiles among patients may lead to an increased chance of toxicity, thus the administration of these medications should be done with the certainty that the occurrence of seizures will be prevented and that the overall benefit outweighs its risk, primum non nocere should always dictate our judgment.
The objective of our study was to investigate the occurrence of post-operative seizures in patients with chronic subdural hematomas treated with burr holes and its relations to pre-operative radiographic findings, morbidities and their follow-up, up to 1 year following intervention.
Materials and methods
A retrospective analysis of the surgical database of the Puerto Rico Medical Center was performed. Medical records of patients with CSDHs admitted to the adult neurosurgery service and treated via burr holes between July 2004 and July 2013 were examined. All patients underwent a standard procedure, which consisted of two burr holes with irrigation of normal saline until clear subdural fluid was seen to confirm maximal drainage, followed by subdural drain placement with an 8-French feeding tube catheter to gravity drainage. Post-operatively, patients were admitted to the intensive care unit, the subdural drain was left in place for 24 h and brain computer tomography (CT) was ordered to evaluate efficacy of subdural evacuation before drainage removal. No CT scans were ordered following drainage removal unless patients developed neurological deterioration. Patients did not receive either pre-operative or post-operative AEDs prophylaxis, and were followed in clinics 2 weeks post-operatively and every 3 months for up to 1 year. Occurrence of a seizure event was recorded and confirmed by history, and a baseline electroencephalography (EEG) was obtained to record any abnormal electrical activity, however EEG was not used to decide if a seizure event had occurred. If patients developed a seizure event they were managed with levetiracetam 1 g (g) twice daily and referred to the epilepsy service after appropriate studies were done to rule out a new surgical lesion. Exclusion criteria included: history of a seizure disorder, previous AEDs use, seizure episode secondary to metabolic disturbances and/or stroke, previous history of intra-parenchymal hemorrhage, traumatic sub-arachnoid hemorrhage or acute subdural hematoma within the past 12 months, and insufficient medical records to determine the presence/absence of seizures pre and post-operatively for up to 1 year. For each patient, age, sex, admission GCS score; dates of seizure events, and antiepileptic drug initiation were recorded. Patient medical histories were also reviewed for pre-operative morbidities. Admission brain CT scans were reviewed for imaging characteristics, including hematoma location, maximal thickness, and midline shift measurements. Institutional review board was obtained to perform study.
Seizure occurrence was identified through the careful analysis of the medical record, including admission history, daily progress notes, and discharge summaries. Statistical analyses were performed using Lilliefors’ composite goodness-of-fit test, Wilcoxon rank-sum test and Fisher’s exact test as appropriate. Statistical significance was defined as a p value <0.05.
Demographical data, radiological parameters
Post-op seizures (−)
Post-op seizures (+)
No. of patients
Mean midline shift
The mean thickness for patients without post-op seizures was 18.4 mm (mean) with a median of 15 mm. For those patients with post-op seizures, the mean thickness was 14.6 mm with a median of 13 mm. These are not statistically different (p = 0.052, Wilcoxon rank-sum test).
The location of the chronic subdural hematoma was on the left side in 116 patients and in the right side in 104 patients. For patients with post-operative seizures, location was on the right in two patients and on the left in three patients. CSDH location was not associated with an increase risk for post-operative seizures (p > 0.05).
The mean midline shift for patients without post-operative seizures was 4.6 mm (mean) with a median of 4 mm. For those patients with post-op seizures, the mean midline shift was 4.2 mm with a median of 5 mm. These are not statistically different (p = 0.90, Wilcoxon rank-sum test). No comorbidities or pre-existing illnesses were independent predictors of seizure occurrence in the post-operative period.
Recurrence of CSDH occurred in 13 patients (6%), and was treated with re-exploration of burr holes. No patients with recurrence of CSDH developed post-operative seizures.
The incidence of post-operative seizures in our series of patients was 2.3%. This is in contrast with reports of up to 12.5% in patients treated via burr holes . Different surgical techniques and variations of the same techniques could account for such differences. It is important to not underestimate the irritative environment caused by blood products on the cortical surface. It is standard in our practice to obtain a through washout of blood products from the cortical surface, minimizing the effect of such irritants. Even then, subdural drains should be left in place for pneumocephalus and for fluid evacuation . Some reports have advocated for decompression alone and gravity suction of blood products with closed drainage systems. We feel this seems to behest the real purpose of surgery and predispose patients to recurrences .
In our study we found no statistically significant difference in location of subdural hematoma with the occurrence of post-operative seizures. The literature seems to be inconsistent in terms of seizure predisposition secondary to the location of the CSDHs [6, 12]. In our cohort, all patients who developed post-operative seizures were males, in contrast to recent reports that showed a tendency towards the female gender in seizure occurrence . We cannot say, however, that there is a statistically significant difference in gender representation, since there are fewer women overall in the study. Most important, due to the low occurrence of post-operative seizures, the administration of AEDs is unnecessarily taking into consideration the side effects of such medications in sharp contrast to previous publications .
In our cohort of patients with CSDHs evacuated via burr holes, we found the incidence of post-operative seizures to be low despite the avoidance of peri-operative AEDs. Also, patients’ demographic and clinical factors did not appear to significantly influence the occurrence of post-operative seizures. The routine administration of peri-operative AEDs must be carefully weighted in patients with CSDH undergoing burr hole evacuation if no risk factor for seizure exists.
Compliance with ethical standards
Conflict of interest
All authors certify that they have no affiliations
with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
All procedures performed in studies involving human
participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study formal consent is not required