Valproic acid-induced hyperammonemic encephalopathy with triphasic waves

Purpose: To examine a patient with valproic acid (VPA)-induced hyperammonemic encephalopathy accompanied by triphasic waves. Methods: A 61-year-old male patient with epilepsy experienced disturbance of consciousness after VPA dose was increased because of poor seizure control. The electroencephalogram (EEG) taken on admission revealed triphasic waves and high-amplitude delta-activity with frontal predominance. Although serum hepatic enzymes, such as AST and ALT, were normal, serum ammonium level was high at 96 mu g/dl (normal range, 3-47 mu g/dl). Serum amino acid analysis showed multiple minor abnormalities. Administration of VPA was discontinued immediately after admission, while other anticonvulsants were continued. Results: The patient's condition was improved on the fourth day of admission. An EEG, serum ammonium level, and amino acid profile were normal on the eighth day. Based on VPA administration, serum ammonium levels, and results of amino acid analysis, this patient had VPA-induced hyperammonemic encephalopathy. Conclusions: Our case indicates that caution is required if triphasic waves appear in VPA-induced hyperammonemic encephalopathy.