Abstracts

Certain neuronal metabolic markers (e.g., NAA [amp] Cr) measured by ¹H magnetic resonance spectroscopy (MRS) have been shown to be highly correlated with EEG abnormalities and degree of atrophy in the brain. A few studies have shown a relationship between MRS brain abnormalities and cognitive performance. This study sought to evaluate the relationship between mesial temporal functional abnormality as measured by MRS and neuropsychological test performance. We hypothesize that epilepsy patients with MRS hippocampal abnormalities will demonstrate worse neuropsychological performance than patients without MRS abnormalities. We further predict that memory function will be disproportionately involved. The sample consisted of 41 epilepsy patients who received both magnetic resonance imaging (MRI) and MRS under an epilepsy imaging protocol. All imaging data were reviewed and interpreted by a neuroradiologist. The region of interest for MRS was the hippocampus on both sides of the brain. All patients were known to or suspected of having localization-related epilepsy of the temporal lobe. Thirty patients showed no abnormality on MRI or MRS (-MRI/-MRS) and 11 had a MRS temporal lobe abnormality (-MRI/+MRS) in the context of a normal MRI. The percentage of patients with left, right, and bilateral MRS abnormality was 36%, 46%, and 18%, respectively. The neuropsychological battery included measures of global cognitive ability, attention-concentration, learning/memory, executive function, speech/language, and information processing speed. The two groups did not differ significantly on age, education, age of seizure onset, seizure duration, or medications. There was a significant difference (p [lt] .05) for gender with the -MRI/-MRS group having a greater proportion of females (73% vs. 27%). Descriptive statistics revealed a clear trend for the -MRI/+MRS group to perform worse than the -MRI/-MRS group on most measures. Univariate statistical analyses showed the -MRI/+MRS group scored significantly lower than the -MRI/-MRS group on measures of verbal memory (p [lt] .01), verbal learning (p [lt] .01), nonverbal memory (p [lt] .05), and visuoconstruction (p [lt] .05). These data indicate the patients who demonstrate functional mesial temporal lobe abnormality as measured by MRS perform worse on neuropsychological testing in general, and more specifically on measures of learning/memory than patients without neuroimaging evidence for either a structural or functional lesion. The MRS offers increased sensitivity to detect mesial temporal pathology that is not obvious on structural MRI imaging. The MRS temporal lobe abnormality in isolation appears to correlate with reduced neuropsychological function, particularly learning and memory. The use of MRS in combination with MRI may be valuable in evaluating progression of mesial temporal pathology.