[Valproate-induced hyperammonemic encephalopathy]

Valproate is a drug commonly prescribed in neurology and psychiatry. Hyperammonemic encephalopathy due to valproate is a severe complication. A 44-year-old man with a past medical history of partial symptomatic epilepsy and alcoholic cirrhosis was admitted for drowsiness. He was receiving valproate and gabapentin. A valproate-induced hyperammonemic encephalopathy was diagnosed on physical examination, generalized slow waves on electroencephalogram and hyperammonemia. Valproate withdrawal led to a progressive recovery of the consciousness, with a rapid normalisation of electroencephalogram and ammonium level. The pathogenesis of this encephalopathy is not clearly established. No correlation has been shown between the severity of encephalopathy, the plasma ammonium level, the valproate dose and its plasma concentration. Additional factors have been pointed out, such as carnitine deficiency or urea cycle enzyme defects. Furthermore, our case suggests an enhancing role of the liver disease in this encephalopathy.