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

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.

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.

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.

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.