[F-18]FDG-PET reveals temporal hypometabolism in patients with temporal lobe epilepsy even when quantitative MRI and histopathological analysis show only mild hippocampal damage

Background: The relationship between reduced glucose metabolism in positron Emission tomography with fludfeoxyglucose F 18 ([(FI)-F-18]FDG-PET) and hi ppocampal damage (HD) in patients with temporal lobe epilepsy is still uncl ear. Objective: To determine whether the presence and severity of HD verified by quantitative magnetic resonance. imaging (QMRI) and histopathological anal ysis affect the degree of hypometabolism. Patients and Methods: Sixteen patients with drug-resistant temporal lobe ep ilepsy underwent [F-18]FDG-PET and QMRI (hippocampal volumetry and T2 relax ometry) before surgery. Histopathological analysis of the hippocampus inclu ded measurements of neuronal loss, proliferation of glial cells, and messy fiber sprouting. The asymmetry in glucose metabolism described the degree o f hypometabolism. Results: Temporal hypometabolism was not related to severity of HD as measu red by QMRI or histopathological analysis. The degree of hypometabolism did not differ in patients with mild, moderate, or severe HD. In addition, [F- 18]FDG-PET revealed significant temporal hypometabolism even though hippoca mpal QMRI findings were normal or showed only mild HD. Thus, glucose consum ption was reduced over and above the histopathological changes. Conclusions: [F-18] FDG-PET is sensitive for localizing the epileptogenic r egion in patients with temporal lobe epilepsy. However, it is insensitive t o reflect the severity of HD.