Prognostic significance of EEG triphasic waves in patients with altered state of consciousness.

Triphasic waves (TWs) are a distinctive, but nonspecific, EEG pattern found in metabolic encephalopathies and a variety of other neurologic conditions. The prognostic value of TWs was studied in 30 patients with altered state of consciousness. Patients were either comatose (18 patients) or very lethargic (12 patients). Triphasic waves were the dominant EEG pattern, present for at least 35% of the tracing. The etiology of their underlying encephalopathy was multiple metabolic derangements (12 patients), hepatorenal syndrome (5 patients), renal failure (4 patients), hypoxic encephalopathy (4 patients), hepatic failure (3 patients), hyponatremia (1 patient), and hypoglycemia (1 patient). Patients were followed up to 22 months. Fifty percent of the subjects died within 30 days of recording TWs. The overall mortality was 77%. Seven patients (23%) have survived, but only three patients (10%) are neurologically normal. In conclusion, TWs occur most often in patients with metabolic encephalopathies, cannot be used to distinguish different diagnostic entities, and indicate a poor prognosis for survival.