REVERSIBLE SIGNAL ABNORMALITIES IN THE HIPPOCAMPUS AND NEOCORTEX AFTER PROLONGED SEIZURES

PURPOSE: To investigate the phenomenon of reversible increased signal intensity of medial temporal lobe structures and cerebral neocortex se en on MR images of six patients with recent prolonged seizure activity , METHODS: After excluding patients with known causes of reversible si gnal abnormalities (such as hypertensive encephalopathy), we retrospec tively reviewed the clinical findings and MR studies of six patients w hose MR studies showed reversible signal abnormalities. MR pulse seque nces included T2-weighted spin-echo coronal views or conventional shor t-tau inversion-recovery coronal images of the temporal lobes. RESULTS : All six MR studies showed increased signal intensity within the medi al temporal lobe, including the hippocampus in five studies. All follo w-up MR examinations showed partial or complete resolution of the hype rintensity within the medial temporal lobe and the neocortex. In one p atient, results of a brain biopsy revealed severe cerebral cortical gl iosis. Temporal lobectomy performed 4 years later showed moderate cort ical gliosis and nonspecific hippocampal cell loss and gliosis, CONCLU SION: Significant hyperintensity within the temporal lobe is demonstra ble on MR images after prolonged seizure activity, suggestive of seizu re-induced edema or gliosis. Damage to medial temporal lobe structures by prolonged seizure activity indicates a possible mechanism of epile ptogenic disorders.