Spike-wave stupor in a patient with metabolic disorder

We report a 79-year-old woman with a decreased level of consciousness. Investigation revealed an elevated serum ammonia and a portal-systemic shunt on angiography. Thus, her symptoms were thought to be due to metabolic encephalopathy. Her electroencephalogram (EEG) showed bilaterally synchronous runs of three-phase waves consistent with the triphasic waves typically seen in metabolic encephalopathy. However, after intravenous administration of diazepam, the EEG abnormalities improved; indicating that her decreased consciousness was of epileptic etiology, consistent with spike-wave stupor. Therefore, even in the presence of a clearly defined metabolic disorder, triphasic waves on the EEG may not be due to metabolic encephalopathy; they may reflect an epileptic state precipitated by the metabolic disorder.