Electrocorticographic evidence and surgical implications of different physiopathologic subtypes of temporal epilepsy

Abstract

Objective: Mesial temporal lobe epilepsy (MTLE) might have a focal or a network physiopathology. Therefore, the objective of this study was to demonstrate that changes in the spiking activity during electrocorticography (ECoG) could reflect changes in the epileptic network, and the resection of the epileptogenic zone could eliminate the mesial spikes.

Methods: Twenty-five MTLE patients were intraoperatively evaluated by ECoG and the mesial strip was maintained until the lateral cortectomy (LC) was completed. Total spiking activity (TSA, mean spikes/min for all the mesial channels) was computed off-line before and after LC. Either a tailored anterior medial temporal resection or LC was carried out based on the TSA changes.

Results: The outcome at 19.1±1.4 months was Engel's class I, 84%; II, 8%; or III, 8%. During the LC, the TSA recorded from the mesial strip did not change in 14 patients, increased in three patients, and decreased in eight patients. In 20% of patients, the mesial activity completely disappeared, and the mesial structures were spared. All of these patients were Engel's class IA.

Conclusions: Our results strongly suggest the existence of physiopathologic differences in MTLE. The identification of these subtypes is fundamental for an individualized surgical approach.

Significance: ECoG would be needed to offer a better surgical approach.

Keywords: Anterior medial temporal resection; Epileptic zone; Etomidate; Lateral cortectomy; Network theory.