Valproic acid-associated hyperammonemic encephalopathy: a case report from the psychiatric setting.

Valproic acid-associated hyperammonemic encephalopathy (VHE) has been described in the neurology and emergency medicine literature, but the case reports identified therein are rarely derived from the psychiatric use of this medication. Valproic acid is widely used as a mood stabilizer in bipolar affective disorder and schizoaffective disorder. Patients with normal blood levels, liver function and metabolic tests may present with markedly elevated ammonia and a variety of neurological symptoms. We report the case of a patient on long-term valproic acid therapy, with stable dosing, who presented with an elevated ammonia level, new-onset tremor, confusion, and loss of consciousness. This case illustrates the need to check ammonia levels in psychiatric patients who are taking valproic acid and who present with new neurological symptoms.