The relationship between quantitative T₂ relaxometry and memory in nonlesional temporal lobe epilepsy

Purpose: We investigated the relationship between preoperative quantitative magnetic resonance imaging (MRI) T₂ relaxometry and volumetry of the hippocampi and pre- and postoperative verbal memory in temporal lobectomy patients who had nonlesional temporal lobe epilepsy. Methods: Pre- and postoperative memory data based on the Logical Memory (LM) subtest of the Wechsler Memory Scale-Revised (WMS-R) and the 30-min delayed recall trial of the Rey Auditory Verbal Learning Test (AVLT) were obtained from 26 left and 15 right temporal lobectomy patients. Coronal MRI T₂ maps were generated for these 41 temporal lobectomy patients as well as 61 control patients. Hippocampal T₂ relaxation times and hippocampal volumes, converted to z scores using control group data, were correlated with neuropsychological performance in the patients. Results: In left temporal lobe-onset patients, high T₂ in the left hippocampal body predicted higher LM performance after surgery. Asymmetrically high T₂ in the left hippocampal body (i.e., the right-minus-left difference), compared with the right hippocampal body, also predicted higher LM performance after surgery. In right temporal lobe-onset patients, high T₂ in the left hippocampal body predicted relatively lower AVLT performance after surgery. Multiple regression analysis in left temporal-onset patients revealed that high T₂ in the left hippocampal body together with higher preoperative LM performance predict higher postoperative LM performance. Conclusions: Our findings suggest that elevated (i.e., abnormal) hippocampal T₂ signal is associated with memory ability (or hippocampal functional capacity) independent of MRI-determined hippocampal atrophy. Therefore, our findings support the use of quantitative T₂ relaxometry as an independent predictor of verbal memory outcome in both left and right TLE patients who are candidates for temporal lobectomy.