THE RELATIONSHIP BETWEEN QUANTITATIVE MRI AND NEUROPSYCHOLOGICAL FUNCTIONING IN TEMPORAL-LOBE EPILEPSY

Purpose: Quantitative MRI techniques provide an unparalleled opportuni ty to examine in vivo the relationship between the extent and laterali ty of hippocampal pathology and associated neuropsychological deficits . The purpose of this study was to examine the nature of the relations hip between quantitative measures of hippocampal pathology and neurops ychological measures, using a multivariate approach. Methods: We exami ned the relationship between two MRI measures of hippocampal structure : hippocampal volumes (HCvol) and T2 relaxation rimes (HCT2), and memo ry performance, in 80 presurgical temporal lobe epilepsy patients. Res ults: As a group, patients with left hippocampal sclerosis (LHS) perfo rmed more poorly that those with right hippocampal sclerosis (RHS) on immediate and delayed prose recall. In the group as a whole, right hip pocampal volume was significantly correlated with the delayed recall o f a complex figure. None of the verbal memory test scores were signifi cantly correlated with the right or left HCvol or HCT2 measures. Howev er, stepwise multiple regression analyses indicated that up to a third of the variation in specific test scores could be explained by the qu antitative MRI hippocampal measures in conjunction with chronological age, and age at onset of habitual epilepsy. Left hippocampal measures explained 24% of the variance in the story-recall tasks, while right h ippocampal measures explained 18% of the valiance in a design-learning task and 32% of the variance in a figure-recall task. Conclusions: Ou r results provide some support for the lateralised model of material s pecific memory deficits, but suggest that a number of demographic and epilepsy-related factors may interact with the extant and laterality o f hippocampal pathology in shaping the nature of the associated neurop sychological deficit.