(1) Objective: This study aimed to explore the efficacy of conventional invasive techniques in confirming unilateral seizure onset localization in mesial
temporal lobe epilepsy with
hippocampal sclerosis (MTLE-HS) and to investigate the association between
electrode type and intracranial electroencephalography (EEG) pattern. (2) Methods: This retrospective study encompasses patients diagnosed with MTLE-HS who underwent an invasive study prior to an
anterior temporal lobectomy (ATL). Intracranial EEG features were assessed for 99 seizure events from 25 selected patients who achieved seizure remission with ATL after an invasive study using bilateral combined depth and subdural
electrodes. Their findings were compared to those of 21 seizure events in eight patients who exhibited suboptimal seizure outcomes. (3) Results: For the distribution of
electrodes that recorded the ictal onset, hippocampal depth
electrodes recorded 96% of all seizure events, while subdural
electrodes recorded 52%. Among the
seizures recorded in subdural
electrodes, 49% were localized in medial
electrodes, with only 8% occurring in lateral
electrodes. The initiation of
seizures exclusively detected in hippocampal depth
electrodes was associated with successful seizure remission, whereas those solely recorded in the lateral strip
electrodes were often linked to refractory
seizures after ATL. (4) Conclusions: These findings emphasize the importance of employing a combination of depth and subdural
electrodes in invasive studies for patients with MTLE-HS to enhance the accuracy of lateralization. This also cautions against sole reliance on subdural
electrodes without depth
electrodes, which could lead to inaccurate localization.