Valproate-induced hyperammonemic encephalopathy treated by hemodialysis

Area of Science:

• Neurology
• Toxicology
• Metabolic Disorders

Background:

• Valproate is a common antiepileptic drug.
• Hyperammonemic encephalopathy is a rare but severe complication of valproate therapy.
• This condition can occur despite normal liver function and therapeutic valproate levels.

Observation:

• An adolescent with absence seizures experienced progressive neurological symptoms after restarting valproate.
• The patient presented with decreased consciousness, vomiting, and significantly elevated ammonia levels (184 micrommol/L).
• Normal liver enzymes and supra-therapeutic valproate levels were noted, alongside carnitine deficiency identified via tandem mass analysis.

Findings:

• Valproate-induced hyperammonemic encephalopathy was diagnosed.
• Continuous generalized slowing was observed on EEG.
• Hemodialysis led to rapid improvement in consciousness and normalization of ammonia levels and EEG.

Implications:

• Carnitine deficiency may be a risk factor for valproate-induced hyperammonemic encephalopathy.
• Physicians should consider valproate-induced hyperammonemic encephalopathy in patients with altered consciousness.
• Prompt diagnosis and intervention, including hemodialysis, are vital for managing this condition.