Abstracts

RATIONALE: To corroborate the results of a recent study involving temporal lobe epilepsy patients which found lateralizing associations between performance on neuropsychological measures and indices of hippocampal metabolism on magnetic resonance spectroscopy (MRS). Particularly, it was hypothesized that left and right hippocampal NAA/Cho would be associated with performance on verbal and nonverbal memory tests, respectively. METHODS: Seven surgical candidates for intractible temporal lobe epilepsy underwent MRS as well as neuropsychological assessment as part of their presurgical work-up. Spectroscopic ratios of N-acetylaspartate to choline (NAA/Cho) were computed for voxels placed in the hippocampus bilaterally, in the seizure focus by magnetoencephalography (MEG), and in the location contralateral to the seizure focus. Thus, the voxels placed on the basis of the seizure focus often overlapped to a degree with those placed in the hippocampi. Cognitive testing included measures of intelligence (Full Scale IQ), verbal (Similarities) and nonverbal reasoning (Matrix Reasoning), verbal (Logical Memory I&II) and non-verbal memory (Rey-Osterreith Complex Figure), attention (Digit Span), processing speed (Digit Symbol), visual confrontation naming (Boston Naming Test), semantic and orthographic fluency, and construction (Block Design). RESULTS: Spearman rank-order correlation coefficients were significant for the following: right hippocampus NAA/Cho and Block Design, seizure focus NAA/Cho and Boston Naming Test, and seizure focus NAA/Cho and orthographic fluency. Marginal significance was found for the associations between: left hippocampus NAA/Cho and Digit Symbol, right hippocampus NAA/Cho and Matrix Reasoning, and contralateral Seizure focus NAA/Cho and orthographic fluency. CONCLUSIONS: Hippocampal NAA/Cho was not associated with verbal and visual memory, perhaps secondary to the limited power afforded by the sample size. However, in agreement with previous research, the results provide support for the for the hypothesis that MRS is sensitive for lateralized cognitive dysfunction.