Emission-computed tomography of fluorine-18-fluorodeoxyglucose and nitrogen-13-ammonia in stroke and epilepsy

The ECAT Positron Tomograph was used to scan normal control subjects, stroke patients at various times during recovery and patients with partial epilepsy during EEG monitoring. Fluorine-18-fluorodeoxyglucose (18FDG) and 13N-ammonia (13NH3) were used as indicators of abnormalities in local cerebral glucose utilization (LCMRsub(glc)) and relative perfusion respectively. In patients with stroke, mean LCMRsub(glc) in the contralateral hemisphere was moderately depressed during the first week, profoundly depressed in irreversible coma, and normal after clinical recovery. Local distributions of 18FDG and 13Nh3 trapping reflected qualitatively the increases and decreases, as well as coupling and uncoupling, expected in stroke for local alterations in glucose utilization and perfusion. Hypometabolism, due to deactivation or minimal damage, was demonstrated with the 18FDG scan in deep structures and broad zones of cerebral cortex which appeared normal on X-ray CT (XCT) and 99Tcsup(m)-pertechnetate scans. In patients with partial epilepsy, who had unilateral or focal electrical abnormalities, interictal 18FDG scan patterns clearly showed localized regions of decreased (20-50%) LCMRsub(glc), which correlated anatomically with the eventual EEG localization. In most instances, these hypometabolic zones appeared normal on XCT and were unchanged on scans repeated on different days. In five of six patients who underwent anterior temporal lobectomy, the interictal 18FDG scan correctly detected the pathologically confirmed lesion as a hypometabolic zone, and removal of the lesion site resulted in marked clinical improvement. In contrast, the ictal 18FDG scan patterns clearly showed foci of increased (82-130%) LCMRsub(glc) which correlated temporally and anatomically with ictal EEG spike foci, and were within the zones of interictal hypometabolism. (author)