Detection of epileptogenic focal cortical dysplasia by depth, not subduralelectrodes

Centers that perform presurgical epilepsy evaluations disagree on whether d epth or subdural electrodes represent the optimal technique for invasive re cording, especially in seizures originating outside the temporal lobe. A 13 -year-old girl with a normal magnet ic resonance imaging scan had unlocaliz ed partial onset seizures, despite scalp and subdural grid ictal video/EEG recordings. Repeat video/EEG with depth electrodes showed a discrete site o f continuous interictal spiking and seizure onset that was located 2-2.5 cm beneath the surface of the sensory cortex. The resected region showed foca l cortical dysplasia and the patient had greater than 95% seizure frequency reduction at 3-year follow-up. We conclude that although subdural electrod es have many advantages when recording seizures outside the temporal lobes, depth electrodes may provide superior recordings when the epileptogenic re gion is beneath the cortical surface.