FDG-PET AND VOLUMETRIC MRI IN THE EVALUATION OF PATIENTS WITH PARTIALEPILEPSY

We performed interictal FDG-PET- and MRI-based hippocampal volumetric measurements on 18 adult patients with complex partial epilepsy of tem poral lobe origin in whom we had identified their ictal focus by video -telemetry EEG. Sixteen patients (89%) had regional hypometabolism, 11 (61%) had focal 1.5-tesla T-2-weighted MRI (two structural abnormalit ies, nine hippocampal formation [HF] increased T-2 signal), and nine ( 50%) had absolute HF atrophy ipsilateral to the temporal ictal focus. Ten (55%) had abnormal L/R HF ratios, nine ipsilateral to the EEG focu s. All patients with abnormal MRI volumetric studies had focal PET abn ormalities. Only seven had both abnormal HF volume ratios and T-2 MRI (all increased HF T-2 signal). There was a significant correlation bet ween hippocampal volume and inferior mesial and lateral temporal lobe cerebral metabolic rate of glucose asymmetry index (p < 0.01), suggest ing that hypometabolism may reflect hippocampal atrophy. PET is more s ensitive than MRI volumetry in identifying the ictal focus but does no t provide additional information when HF atrophy is present.