Valproate-Induced Hyperammonemic Encephalopathy Causing New-Onset Seizures.

Area of Science:

• Neurology
• Toxicology
• Pharmacology

Background:

• Valproic acid (VPA) is a widely used antiepileptic and mood-stabilizing drug.
• Valproate-induced hyperammonemic encephalopathy (VHE) is a rare but serious adverse effect of VPA therapy.
• VHE can occur despite therapeutic VPA serum levels and normal liver function.

Observation:

• A 19-year-old male with bipolar disorder on daily VPA presented with new-onset seizures.
• Laboratory tests revealed elevated blood ammonia levels despite therapeutic VPA concentrations.
• The patient exhibited impaired consciousness and focal neurological symptoms.

Findings:

• Discontinuation of VPA led to the resolution of hyperammonemia and neurological symptoms.
• The case highlights that VHE can manifest even with normal VPA dosing and without hepatic dysfunction.
• Accumulation of toxic VPA metabolites and subsequent ammonia increase are implicated in VHE pathogenesis.

Implications:

• VHE should be considered in the differential diagnosis of altered mental status in patients receiving VPA.
• Awareness of VHE is crucial for clinicians managing patients on VPA therapy.
• Further research into the mechanisms and risk factors of VHE is warranted to improve patient safety.