[C-11]Flumazenil binding in the medial temporal lobe in patients with temporal lobe epilepsy - Correlation with hippocampal MR volumetry, T2 relaxometry, and neuropathology

Objective: To detect reduced [C-11]flumazenil in patients with temporal lob e epilepsy (TLE) and to relate binding to histopathology. Methods: The auth ors studied 16 patients who underwent epilepsy surgery because of drug-resi stant TLE using [C-11]flumazenil PET and quantitative MRI. In 12 patients, resected hippocampus was available for histologic analysis. [C-11]Flumazeni l binding potential (fitted BP) was assessed with the simplified reference tissue model. Results: [C-11]Flumazenil fitted BP in the medial temporal lo be was reduced in all patients with abnormal hippocampal volumetry or T2 re laxometry on MRI. Fitted BP was also reduced in 46% of the patients with hi ppocampal volume within the normal range and in 38% of patients with less t han 2 SD T2 prolongation. In all MRI-negative/PET-positive patients, the hi stologic analysis verified hippocampal damage. Also, [C-11]flumazenil fitte d BP correlated with the severity of reduced hippocampal volume, T2 prolong ation, and histologically assessed neuronal loss and astrogliosis. Conclusi on: [C-11]Flumazenil PET provides a useful tool for investigating the hippo campal damage in vivo even in patients with no remarkable hippocampal abnor malities on quantitative MRI.