Cortical involvement in focal epilepsies with epileptic spasms.

The pathophysiological mechanisms of epileptic spasms are still poorly understood. The role of subcortical structures has been suggested on the basis of non-localized EEG features and from experimental data. The description of asymmetric spasms associated with lateralized EEG patterns has challenged this view and raises the possibility of a cortical origin. This study investigated the cortical organization of partial seizures associated with epileptic spasms in children undergoing intracerebral EEG recordings for presurgical evaluation. Eleven children with drug resistant epileptic spasms and for whom depth electrode recordings were performed were retrospectively studied. In all children several features suggested a focal origin. Cortical involvement was studied using the "Epileptogenicity Index" (EI). A focal origin was finally demonstrated in 10/11 patients. Seven patients demonstrated pre-ictal changes in the seizure onset zone area. EI analysis showed maximal values in the temporal (n=5), parietal (n=1) or frontal (n=5) cortices. EEG changes were also observed in the premotor cortex during spasms in patients with frontal or parietal seizures and in 3/5 patients with temporal lobe seizures. Good surgical outcome (class I or II) was obtained in 7/10 patients. Seizures associated with epileptic spasms may originate from various cortical regions. Premotor/motor cortices are probably involved in determining ictal clinical changes.