Refractory seizures: Prediction of outcome of surgical intervention based on results from PET-CT, PET-MRI and electroencephaolography.

Purpose: The purpose of this article is to evaluate the effectiveness of fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) and PET-magnetic resonance imaging (MRI) with scalp and intracranial electroencephalogram (EEG) in predicting surgical outcomes in patients with refractory seizures.

Methods: Patients who underwent PET-CT and MRI fusion, scalp and intracranial EEG, and subsequent surgical intervention were retrospectively included. PET-CT were fused with MRI and interpreted by an experienced blinded reader. An area of hypometabolism on PET was identified as the location of the epileptic focus. The site of seizure focus was correlated with scalp and intracranial EEG findings. Surgical outcomes were evaluated. Thirty-six patients were included; all had presurgical PET-CT, scalp EEG, and PET-MRI fusion, and 28 of these patients had intracranial EEGs.

Results: PET-CT showed concordance of epileptic foci with scalp EEG in 7/36 patients (19%) and with intracranial EEG in 9/28 patients (32%). PET-MRI was concordant with scalp EEG in 6/36 patients (17%) and with intracranial EEG in 8/28 patients (29%). All patients with concordance of epileptic foci between PET-CT and PET-MRI and scalp EEG had improvement or resolution of seizures postintervention, and 89% of patients had concordance between intracranial EEG and PET studies. However, 45% of patients with discordant PET-CT and scalp EEG, 37% with discordance PET-CT and intracranial EEG, 43% with discordant PET-MRI and scalp EEG, and 35% of patients with discordant PET-MRI and intracranial EEG did not improve postsurgically.

Conclusion: Concordance of epileptic foci localization between PET imaging and EEG yields favorable postoperative outcome in nearly all patients, whereas discordance has an equal probability of favorable vs unfavorable outcomes.