Abstracts

¹H MR spectroscopy is a noninvasive method that can be used to identify neuronal injury and abnormal energetics in the hippocampi of patients with medial temporal lobe epilepsy. Spectroscopic abnormalities in both the sclerotic and contralateral hippocampi have been demonstrated and suggest a pathophysiologic role for metabolic depression, as demonstrated by the ratio of N-acetyl aspartate (NAA) to creatine, in medial temporal lobe epilepsy. These results have led us to examine whether MR spectroscopic data in the diseased or contralateral hippocampi correlate with seizure or cognitive outcome. Significant correlation could allow MR spectroscopy to become a useful preoperative tool to predict seizure and cognitive outcomes following amygdalohippocampectomy in patients with mesial temporal sclerosis and intractable epilepsy. The Yale Epilepsy Surgery database was searched for patients who have undergone 4T ¹H MR spectroscopy and had subsequent medial temporal resections where pathology showed hippocampal sclerosis. The minimum surgical follow-up was one year. Data was collected in this group regarding demographics, pre and postoperative neuropsychologic testing, hippocampal pathology including neuronal and glial cell counts, and seizure outcome. Statistical analyses were used to compare the spectroscopic results, specifically the NAA/Creatine ratio, to seizure and cognitive outcome in this group. Twenty-eight patients were identified who fit the criteria for analysis. Examination of the data showed a significant correlation of temporal lobe specific memory loss as measured by verbal and visuospatial selective reminding test (SRT) with impaired hippocampal energetics as assessed by the NAA/Creatine ratio. There was also a significant correlation between the NAA/Creatine ratio and seizure outcome with minimum follow-up of one year. High field strength MR spectroscopy yields data regarding temporal lobe energetics that correlates with cognitive and seizure outcome following medial temporal resection. MR spectroscopy may therefore be valuable as a preoperative tool better assess surgical outcome in prospective surgical candidates. (Supported by NIH Po1 NS39092.)