IS INTERICTAL TEMPORAL HYPOMETABOLISM RELATED TO MESIAL TEMPORAL SCLEROSIS - A POSITRON EMISSION TOMOGRAPHY MAGNETIC-RESONANCE-IMAGING CONFRONTATION

The mechanism of interictal glucose hypometabolism remains unclear, bu t this abnormality occurs more frequently in temporal lobe epilepsy (T LE) than in other types of partial epilepsy. Therefore temporal hypome tabolism has been suggested to reflect mesial temporal sclerosis (MTS) . To investigate this, we selected 22 patients with refractory partial epilepsy of mesial temporal lobe origin (MTLE) who had hippocampal at rophy based on magnetic resonance imaging (MRI) volumetric analysis. W e then analyzed the metabolic correlates of unilateral hippocampal atr ophy. Thirteen temporal regions of interest (ROI) were defined on MRI scans for each individual and then applied to high-resolution FDG-posi tron emission tomography (PET) images obtained parallel to the long ax is of the hippocampus. The most hypometabolic regions were the tempora l pole and the hippocampal region. When we analyzed ensembles of tempo ral regions grouped into related networks, the temporolimbic network, which included the hippocampal region and the temporal pole, was abnor mal in 95% of the patients at a 3-SD threshold. PET hypometabolism was highly correlated with the degree of hippocampal atrophy in this netw ork, but not in other parts of the temporal lobe, which were less freq uently hypometabolic. These data indicate that hypometabolism is a con sequence of MTS in the temporolimbic region but not necessarily in the other parts of the temporal lobe. Our results also suggest that the c ombination of PET and MRI may facilitate the noninvasive diagnosis of MTLE.