Seizure intractability in patients with mesial temporal lobe epilepsy caused by hippocampal sclerosis as compared to mesiotemporal cavernomas

Introduction: The success of drug treatment is associated to the epilepsy syndrome and the underlying pathology, hippocampal sclerosis being an important risk factor for seizure recurrence. However, other mesiotemporal lesions like mesiotemporal cavernomas are also associated with a higher risk of intractability as compared to patients with extra-mesiotemporal lesions. The aim of the present study was to evaluate differences in seizure control as well as seizure semiology in patients with mesial temporal lobe epilepsy (MTLE) caused by either hippocampal sclerosis or cavernomas.

Methods: Data of eleven patients with mesiotemporal cavernomas and 33 patients with hippocampal sclerosis (sex-matched) were evaluated retrospectively. Drug resistance and seizure freedom after epilepsy surgery were compared using the Mann-Whitney test. Other parameters like seizure semiology, seizure frequency, initial precipitating events and risk factors for epilepsy as well as psychiatric comorbidity were evaluated in an exploratory analysis using χ² and Mann-Whitney tests.

Results: Patients with MTLE caused by HS suffered more often from drug resistance (P=0.003) and tended to be less often seizure free after epilepsy surgery (P=0.036) as compared to patients with cavernomas. The exploratory analysis revealed a somewhat higher percentage of patients with HS to present with aura, especially epigastric aura (P=0.049) and complex partial seizures (P=0.086). Seizure frequency tended to be higher in patients with MTLE due to HS (median seizure frequency 6.5 vs. 1.5 per month, P=0.057) and those patients more often had a history of an initial precipitating event (P=0.034). The other parameters did not show relevant differences between patients with HS and mesiotemporal cavernomas.

Discussion: The results suggest that patients with MTLE caused by HS are more likely to suffer from drug resistant epilepsy as compared to patients with MTLE caused by a cavernoma. Additionally, they tend to show a less favourable postoperative outcome and a higher seizure frequency. This information is important for counselling patients regarding their risk of seizure intractability and their chance to be seizure free after epilepsy surgery.