A Case of Valproate-Induced Hyperammonemic Encephalopathy

A 56-year-old Caucasian male with a history of seizure disorder on long-term prophylaxis with valproate presented with altered mental status, aggressive behavior, decreased oral intake, and frequent myoclonic jerking movements. Electrolyte and other basic metabolic lab testing, liver function testing, and imaging studies were negative for acute abnormalities or infection, though ammonia levels returned markedly elevated, and he also had a macrocytic anemia despite having normal folate and B12 levels. Following discussions with neurology, his valproate was felt to be the inducing factor for his hyperammonemic encephalopathy. After discontinuation of valproate and changing to a new anti-seizure medication, he soon returned to his neurologic baseline. This case report evaluates his presentation and current literature on hyperammonemic encephalopathy induced by valproate.