Abstracts

RATIONALE: Focal hypermetabolism has occasionally been reported in patients with severe partial epilepsy and related to seizures occurring during PET (positron emission tomography). It has been suggested that subclinical discharges may also be associated with focal hypermetabolism but close correlations between hypermetabolic areas and cortical structures displaying subclinical discharges have not been demonstrated. METHODS: Focal hypermetabolism was found in two young adults investigated for chronic drug resistant temporal lobe epilepsy and cortical dysgenesis. Seizure frequency was one per month in patient 1 and one per day in patient 2. Three [18F]-deoxyglucose-PET scans were performed on a head-dedicated PET-camera (Siemens 953B). Patient 1 had two scans at 11 months interval in the same clinical state. MR scans were performed on a 1.5T GE scanner and 3D T1-weighted images were acquired. PET and MR images were superimposed. None of the patients experienced an overt clinical seizure during PET scanning or during the 6 hours before scanning. Surface EEG was recorded before the PET scan and stereo-EEG (SEEG) was performed in both patients after PET investigations. RESULTS: FDG-PET demonstrated a focal area of hypermetabolism (in the amygdala in patient 1 and in the anteromesial part of the temporal lobe in patient 2) surrounded by a large area of ipsilateral hypometabolism. Focal hypermetabolism was found unchanged on both PET scans in patient 1. In both patients, SEEG demonstrated subclinical discharges lasting 1-2 minutes every 7-15 minutes. The location of these subclinical discharges correlated with the hypermetabolic areas. However, hypermetabolic changes were more restricted than the epileptogenic zone and the structural lesions demonstrated by MRI. CONCLUSIONS: During the interictal period FDG-PET may demonstrate localized areas of hypermetabolism related to frequent subclinical discharges.