Value of interictal magnetoencephalography in preoperative evaluation of nonlesional neocortical epilepsy

Abstract

Objective To investigate whether interictal magnetoencephalography (MEG) consistent with surgical range could predict the surgical outcomes in patients with nonlesional refractory neocortical epilepsy (NE).Methods Twenty-five patients with nonlesional NE were studied.All patients had longterm intracranial video-electroencephalography (i-VEEG) monitoring and MEG examinations before surgery.According to the relationship between localization of interictal MEG and surgical range,we divided the participants into two groups,including concordance condition (MEG findings were concordant with surgical range) and discordance condition (MEG findings were discordant with surgical range).Epilepsy surgery was performed to the 25 patient.The surgical outcomes were assessed by neurosurgeons based on over one-year follow-up after surgery using the Engel classification system.Results The total seizurefree (Engel class IA) rate was 36％ (9/25),and the total effective rate was 68％ (17/25).The seizurefree rate of concordance condition was 57％ (8/14),and effective rate was 71％ (10/14).The seizure-free rate of discordance condition was 9％ (1/11),and effective rate was 64％ (7/11).Both the seizure-free rate and effective rate of concordance group were significantly better than those of discordance condition.A statistical difference was found between the seizure-free outcomes of patients with concordance condition and with discordance condition (P ＜ 0.05).Conclusions The study demonstrates that a favorable postsurgical outcome could be prodicted in most patients with concordance of MEG and surgical range. Key words: Magnetoencephalography ; Epilepsy surgery ; Neocortical epilepsy; Nonlesional