Cortical benzodiazepine receptor binding in patients with generalized and partial epilepsy

Impaired cortical inhibition may be involved in epileptogenic mechanisms. In a positron-emission tomography (PET) study, we demonstrated a reduction of the cortical benzodiazepine (BZD) receptor density in the epileptic foci of patients with partial epileptic seizures. In the present study, we used the same method in 10 patients with primary generalized epilepsy to determine whether an altered BZD receptor binding could also be demonstrated in this patient group. The [11C]-labeled BZD receptor antagonist Ro 15-1788 was used as ligand. Receptor affinities and densities were calculated in various cortical regions and then compared with the values from corresponding "nonepileptic" regions in the previously examined partial epilepsy patients. Focal alterations of the BZD receptor density or affinity were not demonstrated in patients with generalized epilepsy. This patient group had a slight tendency toward lower mean cortical BZD receptor density, however, as compared with corresponding values from 10 patients with partial epilepsy. Our results strongly suggest that a focal alteration of cortical inhibition is not a prominent feature of human generalized epilepsy. The observed tendency toward lower mean cortical BZD receptor density may be a consequence of diffusely impaired cortical inhibition. Further investigations of this issue are therefore indicated.