A simplified depth implantation approach in bitemporal lobe epilepsy

Abstract

Background: Up to 73.0% of patients with bilateral temporal lobe epilepsy (BTLE) on scalp electroencephalogram (EEG) were found to have unilateral temporal seizure onset via invasive EEG monitoring (iEEG) and 58% of them achieved good surgical outcome. However, iEEG in resource- limited countries is limited by cost. We aimed to present the surgical outcome of a simplified and cost- effective 2-electrode bilateral hippocampal depth implantation strategy in 7 cases with bilateral temporal lobe epilepsy based on scalp EEG and unilateral mesial temporal sclerosis (MTS). Methods: Total 7 cases who underwent epilepsy surgery were reviewed. All patients underwent 2-stage evaluation of video-EEG monitoring followed by intracranial monitoring. A simplified 2-depth electrode implantation strategy was used, targeting the bilateral anterior hippocampus. Results: All 7 patients had interictal bilateral independent temporal epileptiform discharges. Four had bilateral temporal ictal onset on scalp EEG and 3 with ictal onset contralateral to the MTS. With iEEG, 4 patients (57.1%) were confirmed to be unilateral TLE, concordant with the MTS, and 3 patients (42.9%) had true BTLE. All 7 patients underwent anterior temporal lobectomy, ipsilateral to the side of MTS. Four patients (57.1%) achieved Engel I surgical outcome, of which 3/4 (75.0%) were patients with unilateral TLE. For those with true BTLE, 2/3 (66.7%) achieved favourable surgical outcome (Engel I and II). Conclusions: This simplified two-electrode implantation strategy is effective in lateralization of TLE in patients with BTLE and more affordable to those in resource-limited countries.