Secondary epileptogenesis in cerebral arteriovenous malformations.

There is debate as to whether secondary epileptogenesis occurs in humans. As part of a series of patients with cerebral arteriovenous malformations and epilepsy, we identified two patients with probable secondary epileptogenesis in the mesiotemporal regions, ipsilateral but anatomically distant from an arteriovenous malformation causing seizures. Both patients had arteriovenous malformations outside the mesiotemporal region and resection of the arteriovenous malformation and epileptogenic areas identified by electrocorticography produced initial freedom from seizures. Three to 6 months later both patients developed a different seizure pattern that proved to be mesiotemporal in origin by video/electroencephalogram (one with depth electrodes) and both patients are seizure free after a second resection of anterotemporal and mesiotemporal regions. Findings indicating a secondary epileptogenic focus include (1) different seizure type by patient history, (2) second seizure type by ictal video/electroencephalographic recordings, and (3) lack of pathologic abnormalities in the resected mesiotemporal specimens.