Reduction of benzodiazepine receptor binding is related to the seizure onset zone in extratemporal focal cortical dysplasia

Purpose: Comparison of regional reduction of GABA receptor binding and seizure onset zone in patients with extratemporal epilepsy due to focal cortical dysplasia. Methods: Two patients with frontal lobe epilepsy who remained seizure free after partial frontal lobe resection were investigated with magnetic resonance imaging, positron emission tomography (PET) with ¹⁸F-fluoro-deoxy-glucose (FDG) and ¹¹C-flumazenil, subdural EEG-video recordings, and postoperative benzodiazepine (BDZ)-receptor autoradiography. Results: The area of reduced BDZ-receptor binding as documented by preoperative flumazenil-PET and postoperative BDZ-receptor autoradiography corresponded to the seizure on- set zone and was smaller than the interictal hypometabolism documented by FDG-PET. Conclusion: Flumazenil-PET is a useful tool for localization of the epileptogenic zone in patients with extratemporal epilepsy caused by focal cortical dysplasia. Neuronal distribution of BDZ-receptor density confirms in vivo flumazenil-PET findings. The regional reduction of BDZ-receptor binding in focal cortical dysplasia seems to be confined to the seizure onset zone and not to the extent of dysplastic cortex.