Interictal and postictal (18)F-FDG PET/CT in epileptogenic zone localization

OBJECTIVE: To evaluate the performance of (18)F-fluorodeoxyglucose positron-emission tomography/computed tomography ( (18)F-FDG PET/CT) in localizing epileptogenic zones, comparing (18)F-FDG injection performed in the traditional interictal period with that performed near the time of a seizure. MATERIALS AND METHODS: We evaluated patients with refractory epilepsy who underwent (18)F-FDG PET/CT. The reference standards for localization of the epileptogenic zone were histopathology and follow-up examinations (in patients who underwent surgery) or serial electroencephalography (EEG) recordings, long-term video EEG, and magnetic resonance imaging (in patients who did not). The (18)F-FDG injection was performed whether the patient had an epileptic seizure during the EEG monitoring period or not. The (18)F-FDG PET/CT results were categorized as concordant or discordant with the reference standards. RESULTS: Of the 110 patients evaluated, 10 were in a postictal group (FDG injection after a seizure) and 100 were in the interictal group. The (18)F-FDG PET/CT was concordant with the reference standards in nine (90%) of the postictal group patients and in 60 (60%) of the interictal group patients. Among the nine postictal group patients in whom the results were concordant, the (18)F-FDG PET/CT showed hypermetabolism and hypometabolism in the epileptogenic zone in four (44.4%) and five (55.6%), respectively. CONCLUSION: Our data indicate that (18)F-FDG PET/CT is a helpful tool for localization of the epileptogenic zone and that EEG monitoring is an important means of correlating the findings. In addition, postictal (18)F-FDG PET/CT is able to identify the epileptogenic zone by showing either hypometabolism or hypermetabolism.