Abstracts

RATIONALE: The surgical management of neocortical epilepsy is challenging because many patients are without obvious structural lesions, or lesions are small and easily overlooked during routine clinical interpretation of MRI data. Even when functional imaging data suggest focal epileptiform pathology, in the absence of a concordant structural lesion, invasive monitoring is often required to confirm that an appropriate surgical target has been identified. This study sought to determine the extent to which knowledge of magnetoencephalographic (MEG) data can augment the MRI-based detection of structural brain lesions.
METHODS: MRI and whole-head MEG data were obtained from 40 patients with neocortical epilepsy. MRI data were obtained using a 1.5T whole-body imaging system and were initially reviewed by a CAQ-certified neuroradiologist. At the time of initial review, the interpreting neuroradiologist had knowledge of the patient[ssquote]s epileptic history, but was without explicit knowledge of MEG findings. Whenever MEG indicated epileptiform activity in a zone that had not been identified to have a structural lesion, the MRI data were re-evaluated, now with explicit knowledge of the MEG findings. Specifically, the neuroradiologist was shown magnetic source localization images that displayed the MEG-derived sources of epileptiform activity on spatially aligned magnetic resonance images, and he was asked to re-evaluate the MR data in the MEG implicated regions.
RESULTS: As a result of MEG data, 29 cases were sent for MRI re-evaluation. In 7 of these cases, MEG-guided review led to specification of now clear, but previously unidentified lesions. There were two additional cases where MEG-guided review of the study MRI led to identification of an unusual looking area, but in both cases follow-up high-resolution imaging did not confirm structural abnormalities.
CONCLUSIONS: In patients with neocortical epilepsy, MEG is a useful adjunct to MRI for the identification of structural lesions.