Subtemporal hippocampectomy preserving the basal temporal language area for intractable mesial temporal lobe epilepsy: preliminary results

PURPOSE: Decline in verbal memory as a surgical complication remains an unresolved problem in mesial temporal lobe epilepsy. Some areas in the temporal lobe associated with the language function, often including the basal temporal language area, have been removed or transected by conventional surgical procedures. The authors defined the basal temporal language area and removed only the epileptogenic zone with a subtemporal approach. METHODS: The basal temporal language area was evaluated by using long-term subdural electrodes in five patients with language-dominant-side mesial temporal lobe epilepsy. While preserving this area, the hippocampus and the parahippocampal gyrus were removed by using a combined subtemporal, transventricular, transchoroidal fissure approach. Verbal memory performance was assessed with the Wechsler Memory Scale-Revised (WMS-R) before and after the operation. RESULTS: The basal temporal language area, defined as a part of the inferior temporal gyrus, the fusiform gyrus, and the parahippocampal gyrus, was spared by entering the temporal horn via collateral sulcus. Verbal memory was significantly improved by 3 months and 1 year after the operation. CONCLUSIONS: In language-dominant-side mesial temporal lobe epilepsy, preserving the basal temporal language area would have potential to improve verbal memory outcomes after removal of the epileptogenic zone.