[C-11] FLUMAZENIL POSITRON EMISSION TOMOGRAPHY VISUALIZES FRONTAL EPILEPTOGENIC REGIONS

Presently available noninvasive methods correctly localize epileptogen ic regions in only similar to 50% of patients with frontal lobe epilep sy (FLE). Earlier studies have shown that temporal lobe epileptogenic regions may be identified readily by positron emission tomography (PET ) measurements of regional benzodiazepine (BZD) receptor binding. We t ested the specific applicability of this method in patients with FLE. Six patients with frontal partial seizures and 7 healthy men were inve stigated with PET and the BZD receptor ligand [C-11]flumazenil. All pa tients had magnetic resonance (MR) brain scans. The independent assess ment of seizure-onset region was based on seizure semiology, intra- an d extracranial EEG and, in 4 cases, also on [F-18]fluorodeoxyglucose ( FDG)-PET. The epileptic focus/seizure-generating region was correctly identified by [C-11]flumazenil PET in all patients. This region was ch aracterized by a significant reduction in BZD receptor density. The ar ea with reduced BZD receptor density was better delimited than the cor responding hypometabolic region, which was observed in 50% of patients investigated with [F-18]FDG-PET. MRI was normal in 5 patients. Visual ization of BZD receptors with [C-11]flumazenil PET appears to be a pro mising approach for noninvasive identification of frontal lobe epilept ogenic regions.