Diagnostic Subdural EEG-electrode And Subdural hEmatoma (DISEASE): Study Protocol for Prospective Non-randomized Controlled Trial

Epileptic seizures are one of the frequent complications in patients with traumatic brain injury; the incidence lies approximately at 20%. Particularly, acute subdural hematoma (aSDH) is one of the most important predictors for epileptic seizures, which is besides other parameters like age, preoperative Glasgow coma scale, cerebral herniation, hematoma volume and time to operation, associated with worse neurological outcome. In a recent systematic review, the mean incidence of epileptic seizures in aSDH was 28%, whereas one retrospective study focusing on EEG-diagnostic reported very high incidence of epileptiform abnormalities on surface EEG in 87% of patients with aSDH, wherefore the question rises, if the incidence of epileptic seizures is underestimated.

Despite successful evacuation of subdural hematoma, approximately one third of patients show no clinical improvement without medical explanation. Routinely, surface spot EEG is performed to detect epileptic seizures; however the sensitivity is limited due to the skin-bone barrier and the short duration of recording. Furthermore, surface EEG is not always available, for example during the night or at weekends, which is an additional limitation for the loss of treatment timing as well. Spot surface EEG will record for only 20 to 30 minutes in contrast to continuous EEG recordings that are performed for hours or days.

Due to the clinical relevance of epileptic seizures, several studies investigated the benefit of prophylactic antiepileptic treatment. To date, there is only one recommendation from the Brain Trauma Foundation at evidence class II to treat patients with severe traumatic brain injury with prophylactic antiepileptic treatment during the first week. Beyond the interval; there was no clinical benefit for patients selected. Still, there are some limitations´wherefore the clinical use of prophylactic antiepileptic treatment varies between clinicians and countries. At that time, the standard medication was phenytoin which has several side effects, but to date, there are several new intravenous antiepileptic drugs with comparable effect but better safety profile. On the other hand, there was no sifferentiation made between high-risked seizure prone patients, like patients with aSDH, and low-risked patients which is one of the limiting factors to support a general recommendation. Therefore the role of prophylactic antiepileptic treatment is still questionable.

In the clinical routine, invasive EEG-electrodes are commonly used to detect epileptic focus. The benefit of those electrodes is the real time analysis in case of seizure occurrence compared to surface EEG. Moreover, therapeutic effect is directly visible through the monitoring. Therefore the idea of this study was to make a real time analysis possible for patient with TBI, particularly aSDH, to have diagnostic and therapeutic real time monitoring detecting subclinical seizures.