Utilization of multichannel magnetoencephalography in the guidance of ablative seizure surgery

Magnetoencephalography (MEG) was used to evaluate 50 seizure surgery candidates. Interictal spikes were recorded in 42 cases. Of 20 cases with other data suggesting a convexity (lateral neocortical) focus, MEG spikes were recorded from 19. In 17, MEG and electrographic data were localized to the same region. Invasive studies were or could have been avoided in 11 cases based on MEG and other noninvasive data. MEG spike data were present in 14 of 18 cases with anteromesial temporal foci, being localized to the same lobe as electrographic data in 11. MEG was not of value in surgical planning of cases with orbitofrontal foci, or depth nonlocalized seizures. Twenty-seven patients with MEG epileptiform data have had postoperative follow-up. Fourteen of 19 with electrographic and MEG data localized to the same region are seizure-free. Four of eight with spatial discordance of MEG and electrographic data are seizure-free. Preliminary conclusions are as follows: When MEG and electrographic data are localized to the same region, seizure-free surgical outcome is more likely. In convexity cases with MEG and noninvasive electrographic data localized to the same region, preoperative invasive studies may be unnecessary.