Abstracts

Transsylvian selective amygdalohippocampectomy (TSA) is a surgical technique for intractable mesial temporal lobe epilepsy that allows preservation of the lateral cortex of the temporal lobe. However, because the temporal stem is partially severed, concern has been expressed that temporal lobe function may be compromised. The usefulness of TSA was thus investigated by analyzing cognitive function and changes in brain metabolism in the temporal lobe before and 1 year after TSA. In 32 patients who had been diagnosed with unilateral mesial temporal lobe epilepsy and underwent TSA, intelligence and memory tests were administered to assess cognitive function, and fluorodeoxyglucose positron emission tomography (FDG-PET) was performed to examine brain metabolism before and 1 year after TSA. The WAISR was used to assess intelligence, while the Miyake Verbal Memory Test and the Benton Visual Memory Test were used to evaluate memory function. Brain metabolism was assessed by comparing a ratio of the radioisotope counts of mesial and lateral ipsilateral temporal lobe to brain stem. IQ increased postoperatively irrespective of whether TSA was performed on the left or right side. When TSA was performed on the right side, verbal memory score increased significantly. When TSA was performed on the left side, verbal memory score tended to decrease slightly, but no significant change was noted. No significant decreases in visual memory score were identified irrespective of TSA laterality. Regarding brain metabolism, radioisotope count significantly decreased for the medial temporal lobe, as this area was surgically severed, but no clear decrease in radioisotope count was noted for the lateral residual temporal lobe. Intelligence and memory are conserved following TSA, and partial severing of the temporal stem does not affect brain metabolism in the temporal lobe. As the range of resection is narrow in the treatment of unilateral mesial temporal lobe epilepsy, TSA is minimally invasive and very useful from the perspective of preserving brain function.