Cortical benzodiazepine receptor changes are related to frequency of partial seizures: a positron emission tomography study.

Measurements of benzodiazepine (BZD) receptor density with positron emission tomography (PET) are a promising method of identifying and localizing epileptogenic regions. We investigated whether the pattern of BZD receptor changes depends on seizure frequency, studying 19 patients with matching seizure semiology but different rates of seizure occurrence, using [11C]flumazenil as the ligand. All patients had partial epilepsy and normal magnetic resonance imaging (MRI) of the brain. The visually determined PET focus, characterized by reduced BZD receptor density, corresponded to the epileptogenic focus/seizure onset region in all patients. The degree of BZD receptor reduction showed a positive correlation with seizure frequency. Patients with daily seizures differed from those with fewer seizures in two aspects: (a) the degree and extent of BZD receptor reduction was more pronounced, and (b) BZD receptors were also reduced in the primary projection areas of the focus. Flumazenil-PET reliably identifies epileptogenic brain regions in patients with partial seizures. In addition, flumazenil-PET can distinguish patients with frequent seizures. The method therefore is not only suitable for noninvasive localization of the seizure focus, but also may provide a biochemical marker of epileptogenicity.