Abstracts

RATIONALE: Patients who undergo temporal lobectomy show varying degrees of memory impairment pre- and post-operatively. We investigated verbal and visual memory changes as assessed by neuropsychological testing in patients who underwent temporal lobectomy. The relationship between pattern of hippocampal involvement (bilaterally small symmetric, bilaterally large symmetric, and bilaterally asymmetric) and memory scores was analyzed. METHODS: 72 patients who underwent temporal lobectomy (37 right, 35 left) were selected retrospectively. These patients were further divided into three groups based on MRI based hippocampal volumes; symmetric small (n=13), symmetric large (n=13), and asymmetric (n=46). Memory scores from pre- and post-operative assessments (Weschler Memory Scale-Revised) were analyzed and compared using standardized regression based norms. RESULTS: There was a significant relationship between side of resection and both verbal and visual memory score outcome. Left temporal lobectomy patients showed decreases in verbal memory and right temporal lobectomy patients showed decreases in visual memory. Patients with asymmetric hippocampal volumes (left < right) tended to have less verbal memory decline following left temporal lobectomy when compared to patients with symmetrical hippocampal volumes. Patients with symmetrical large hippocampi tended to have greater decline in delayed verbal memory scores following left temporal lobectomy when compared to patients with symmetrical small hippocampi. No consistent pattern of memory change was seen between hippocampal volume groups among patients who underwent right temporal lobectomy. CONCLUSIONS: Side of temporal surgery correlates with verbal and visual memory outcome. Patients with symmetrical hippocampal volumes (large more so than small) tend to be at greater risk for verbal memory decline after temporal lobectomy when compared to patients with asymmetric hippocampal involvement. Larger sample sizes are needed to better characterize the relationship between symmetric small hippocampi and symmetric large hippocampi and memory outcome.