Acute depth electrode investigations in temporal lobe epilepsy: Correlation with magnetic-resonance-imaging-based volume studies and pathology

We performed a retrospective study correlating acute depth electrode recordings with histopathology and magnetic-resonance-imaging-based volume measurements of the hippocampal formation in 20 patients with intractable partial epilepsy who subsequently underwent an anterior temporal lobectomy. Patients with mass lesions of extrahippocampal pathology were excluded from this study. Fifteen patients had pathological alterations consistent with mesial temporal sclerosis, and five patients had gliosis with less than 50% hippocampal neuronal loss. Intraoperative depth electrode spiking was analyzed for the frequency and morphology of the epileptiform activity. A highly significant correlation was demonstrated between spike frequency and the severity of the hippocampal pathology (p = 0.002). Patients with mesial temporal sclerosis and hippocampal formation atrophy identified by magnetic resonance imaging statistically had more active mesiotemporal spiking (p = 0.005 and p = 0.007, respectively). Acute depth electrode investigations may have diagnostic utility in patients with intractable partial epilepsy of temporal lobe origin.