Use of interictal 18F-fluorodeoxyglucose (FDG)-PET and magnetoencephalography (MEG) to localize epileptogenic foci in non-lesional epilepsy in a cohort of 16 patients

We assessed the efficacy of interictal 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) and magnetoencephalography (MEG) for localizing the epileptogenic foci in a small cohort of patients with non-lesional epilepsy. Sixteen patients, aged 8-32 years, with non-lesional epilepsy underwent MRI, continuous scalp video-electroencephalography (EEG) monitoring, interictal (FDG)-PET and MEG at our institution. Each patient subsequently underwent intracranial grid placement. The data from the intracranial grids was correlated with the previous studies to determine the efficacy of FDG-PET and MEG in localizing the epileptogenic zone. Of the 16 patients, the epileptogenic zone was accurately localized in 8 (50%) using FDG-PET and in 12 patients (75%) using MEG. Of the 11 patients with a temporal hypometabolism, only 4 were ultimately confirmed as temporal lobe epilepsy via intracranial grids and 2 additional patients were found to have extra-temporal lobe epilepsy. Compared to interictal FDG-PET, MEG appears to be more sensitive to detection of the epileptogenic zone in this small cohort of non-lesional epilepsy patients though provided more diffuse foci. Our findings can help in determining the surgical eligibility of a patient especially when MRI or video-EEG monitoring are non-localizing, and can help with placement of subdural grids and strips for EEG studies.