Abstracts

Memory assessment is critical in the surgical work-up of patients with temporal lobe epilepsy (TLE), not only to help identify lateralization of seizure focus but to identify patients at risk for cognitive morbidity, in particular, material specific memory declines. Efforts to predict decline in verbal memory associated with temporal lobectomy have included various in-vivo methods of assessing structural and functional changes associated with MTS, such as volumetric measures, and metabolic changes. More recently, MR spectroscopy measures, when combined with other measures of pathology, have been investigated with mixed results. The goal of the present study is to examine the relationship between functional verbal memory, as measured by the verbal Selective Reminding Test (vSRT), MRS, and hippocampal volume in patients with medically intractable TLE.
Hypotheses:
A. In patients with left TLE, pre-surgical verbal memory scores on the SRT will be positively correlated with measured NAA/Cr levels from ipsilateral hippocampus.
B. In patients with left TLE, ipsilateral hippocampal volume will be positively correlated with verbal memory scores., Sixteen patients underwent comprehensive evaluation at the Yale Epilepsy Center and subsequently underwent surgical management for TLE (left 8, right 8). Standard anterior medial temporal resection was performed in all patients, except for two, who underwent additional lateral neocortical resection as tailored by pre-operative electrophysiological localization. Pre-op, MR spectroscopic data was acquired at 4 Tesla and analyzed in blinded fashion by independent observer. Single voxel data (measured NAA/Cr values averaged over 3 mid hippocampal loci) was used for correlation with memory scores. Intracarotid amobarbital procedures (IAP) were performed. Patients were evaluated before and one year after surgery. Neuropsychological testing included the WAIS and the vSRT., Bivariate correlations show that in patients with left TLE, NAA/Cr levels in the ipsilateral hippocampus were positively correlated with pre-surgical verbal memory scores (r = .867, p = .005). Ipsilateral hippocampal volume was not related to verbal memory, or NAA/Cr levels (r = .536, p = .110)., Patients with left TLE showed a positive relationship between [sup1]H MRS ratios and verbal memory, indicating that NAA/Cr levels in the hippocampus may be useful as a proxy for measurement of functional verbal memory, and can help identify functional deficits in epilepsy surgery candidates. However, a relationship between ipsilateral hippocampal volume and [sup1]H MRS was not found. This suggests that NAA/Cr levels and volume may be measuring different aspects of hippocampal pathology (i.e., functional vs. structural).,