Contribution of FDG-PET in epilepsy surgery: consistency and postoperative results compared with magnetic resonance imaging and electroencephalography.

Aim: Surgery is a treatment option for medically intractable epilepsy patients. Abnormalities in regional cerebral glucose metabolism, as identified by 18-fluorodeoxyglucose positron emission tomography (FDG-PET) have predictive prognostic value in evaluating the outcome of epilepsy surgery. This study investigated the efficacy of FDG-PET for delineation of the epileptogenic zone (EZ) by comparing its consistency with other diagnostic tools and surgical outcome.

Material And Methods: We analyzed the results of 121 consecutive patients evaluated for epilepsy surgery. FDG-PET results were crosschecked with magnetic resonance imaging (MRI) and electroencephalography (EEG) results, as well as postoperative outcome and pathology.

Results: FDG-PET findings of 75 patients (62 %) were concordant with MRI (Mc-Nemar-χ2 test p=0.024, Kappa=0.22). Further, the PET findings were consistent with EEG, and was statistically significant, according to Post-hoc test, in temporal epilepsy (TLE) group (χ2=8.21 P=0.04). Both investigations revealed localizing information in 56 (46.2%) patients. Twenty-six (72.2%) MRI-negative patients had hypometabolism on PET. The pathology of the 10 PET-negative patients was 5 cases of mesial temporal sclerosis, 2 cortical dysplasia, 2 gliosis and one tumor. Seven (70%) of these patients' lesions originated from the temporal lobe. FDG-PET had correctly predicted the EZ in 37 (86%) of 43 patients who underwent surgery.

Conclusion: FDG-PET results may not be strongly associated with EZ but represent an additional tool in delineation of EZ during the noninvasive phase of presurgical evaluation.