Positron emission tomography: Comparison of clinical utility in temporal lobe and extratemporal epilepsy

Sixty consecutive patients admitted for possible surgical treatment of intractable epilepsy underwent ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) as part of a standardized presurgical protocol. Patients were classified as having temporal lobe or extratemporal epilepsy based on all available information excluding PET. Of 35 patients categorized as having temporal lobe epilepsy, 27 (77%) had unilateral temporal lobe hypometabolism that always correlated with electrophysiologic localization of the seizure focus. In 19 patients categorized as having extratemporal epilepsy, only six (32%) had an abnormal PET study and in only one patient did PET assist in subsequent localization of the seizure focus. Four patients with extratemporal epilepsy had falsely localizing information obtained on PET. The results of this study demonstrate that PET is of less clinical utility in the presurgical evaluation of patients with extratemporal epilepsy as compared to patients with temporal lobe epilepsy.