Understanding the relationship between measures of biological activity and psychological phenomena is currently of major interest to clinical neuropsychologists. Sclerosis of the hippocampus in temporal lobe epilepsy is an opportunity to examine the consequence of this pathology on biological and neuropsychological functioning. The prediction of cognitive morbidity post temporal lobectomy is also of interest when surgery is indicated in medically refractory epilepsy. Seventeen (17) patients with temporal lobe epilepsy were examined at the Yale Epilepsy Center and were administered the Selective Reminding Test as part of a comprehensive neuropsychological evaluation. Patients also underwent neuroimaging protocols, which included the acquisition of structural volumetrics and magnet resonance spectroscopy (MRS) levels of N-acetyl-aspartate (NAA) and creatine (Cr). All patients subsequently underwent temporal lobectomy. Results indicate that, in patients with left temporal lobe epilepsy, NAA is significantly related to verbal memory, but not to left hippocampal volume. No significant relationships are observed between right hippocampal volume, non-verbal memory, and levels of NAA in right hippocampus. An exploratory multiple regression was also conducted, with post-operative verbal memory as the outcome and left hippocampal NAA, left hippocampal volume, and presurgical verbal memory as predictors, which did not reach significance, possibly due to small sample size. It is concluded that (1) the SRT is a valuable non-invasive tool for seizure lateralization, (2) assessing NAA levels may provide valuable insight into the biological underpinnings of a psychological phenomenon, (3) that although a valid model of prediction was not demonstrated here, that NAA levels may be of use in future studies to aid in prediction of cognitive decline, and (4) NAA may be a more accurate predictor of hippocampal functionality than structure.
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