Hippocampal volume and glucose metabolism in temporal lobe epileptic foci

Purpose: Reports conflict on the relation of glucose metabolism to hippocam pal volume in temporal lobe foci. Previous studies usually have used side-s ide ratios rather than regional metabolic rates. Methods: We measured hippocampal volume and glucose metabolism in 37 patien ts with temporal epileptogenic zones identified by ictal video-EEG telemetr y. Metabolic rates were normalized to global brain mean. Results: Both 18-fluoro-2-deoxyglucose-PET and volumetric MRI lateralized t he epileptic focus determined by ictal video-EEG. There were significant co rrelations between left-right metabolic asymmetry and hippocampal formation volume left-right ratios. Comparisons between normalized metabolism and hi ppocampal formation volume, ignoring the side of the epileptic focus, showe d significant relations between left hippocampal volume and left inferior l ateral temporal metabolism, right hippocampus and right inferior mesial tem poral, and left hippocampus and left inferior mesial temporal metabolism. I n contrast, when normalized metabolism was compared with hippocampal volume in the epileptic focus, no relation was found. Conclusions. Our study suggests that the relation between hippocampal volum e and glucose metabolism breaks down in epileptic foci and that hypometabol ism is not dependent on neuronal loss. It is consistent with data suggestin g that hypometabolism is an independent predictor of surgical outcome.