ABSTRACT
BACKGROUND: This study was performed to investigate the relationship between the extent of hippocampal resection and the postsurgical memory outcome in temporal lobe epilepsy (TLE). METHODS: In 36 patients with TLE, the longitudinal distances of pre-surgical hippocampus and post-surgical hippocampal remnant were measured on 3 mm thick coronal MRI images perpendicular to the long axis of hippocampus. Memory tests were performed before and 1 year after the surgery. The relationships of the extent of hippocampal resection (EHR) and the asymmetry index of Wada retention memory scores (WAI) with postsurgical memory outcomes were tested. RESULTS: The ratios of post-surgical/pre-surgical scores in immediate and delayed verbal memory and immediate, delayed and recognition visual memory were not significantly correlated with the EHR. Only verbal recognition memory was positively correlated with the EHR. In TLE of the dominant hemisphere, the ratios of post-surgical/pre-surgical scores of verbal and visual memories were not significantly correlated with the EHR, but the WAIs were significantly correlated with the delayed visual memory changes (p<0.05). In TLE of the non-dominant hemisphere, the ratios of post-surgical/pre-surgical scores of delayed verbal and immediate visual memory (in percentiles) were positively correlated with the EHR (p<0.05). However, a linear regression analysis showed that none of postsurgical memory subtypes were significantly correlated with the EHR. CONCLUSIONS: This study suggests that the extent of hippocampal resection itself does not have a significant relationship with the outcome of postsurgical memory in patients with mesial TLE.