Case Report: Valproate Induced Hyperammonaemic Encephalopathy in a Psychiatric Inpatient

We present the case of a young gentleman admitted to an inpatient psychiatric ward with a diagnosis of Bipolar Affective Disorder who developed Valproate-induced Hyperammonaemic Encephalopathy (VHE) alongside infection with COVID-19. His condition had exhibited a relapsing and remitting course, relapses being associated with non-compliance with prescribed medication and substance misuse. He had previously been successfully treated with a combination of antipsychotic (haloperidol) and semi-sodium valproate which were re-prescribed following the index admission to hospital. On this occasion however both his mental and physical health began to deteriorate, with evidence of irritability and over-sedation, disorientation, and significantly impaired cognition. On examination, reduction in visual fields was noted, and after bloods, MRI scanning and a review by neurology, he was diagnosed with hyperammonaemic encephalopathy. This was suspected to be an adverse effect of the Depakote. Following transfer back to the psychiatric hospital, he was cross titrated off Depakote and on to Lithium, and the cognitive disturbance remitted. This case adds to the existing literature on the potential challenges in diagnosing this rare but potentially fatal reaction to valproate, in a psychiatric inpatient population for which data on VHE is limited. Psychiatrists should keep a high index of suspicion for VHE in those taking Valproate who show new signs of a deterioration in mental status. Early diagnosis and withdrawal of valproate are key in manifesting a prompt and complete recovery. While neurologists are familiar with this complication we believe this is not well known among psychiatrists and therefore worthy of adding this case report to the existing literature.