Neuromagnetic localization of spike discharges correlates with postoperative seizure outcome

Spike source estimation determined by preoperative magnetoencephalography (MEG) was compared to the postoperative seizure outcome in 17 patients with intractable epilepsy. Interictal spike discharge was analyzed during the period from the early slope to the spike peak, using a single dipole model applied to each hemisphere of the helmet-shaped MEG data. According to the accumulation deta of 80% of the spike dipoles, each patient was classified into one of three groups. 'Regional' accumulation was found in 8 cases with temporal lobe epilepsy (TLE), who were completely seizure-free following anterior temporal lobectomy (ATL). 'Lobar' accumulation was found in 3 cases with TLE and 1 case with frontal lobe epilepsy. These cases resulted in a complete seizure-free diagnosis in 3 cases of the and a worthwhile seizure reduction in the other 1 case. 'Multilobar' accumulation was found in 4 cases. Unilateral ATL or frontal lobe resection was performed in these cases. Among them, 1 case became completely seizure-free but the other three cases had residual seizures. Our present analysis of the MEG spikes disregarded possible propagation of spike discharges, but enabled us to predict postsurgical seizure outcomes in a practical and simple way. Surgical indication for epilepsy, however, must be decided with the aid of other clinical findings.