Non-convulsive status epilepticus secondary to valproic acid-induced hyperammonemic encephalopathy.

BACKGROUND: Valproic acid (VPA) may induce hyperammonemic encephalopathy. On the other hand, seizure-inducing effects of antiepileptic drugs (AEDs) may be a paradoxical reaction or a result of AED-induced encephalopathy (commonly induced by VPA).

METHODS: We present the case of a 19-year-old male who developed acute mental status changes consistent with encephalopathy evolving into repetitive seizures with oral automatisms induced by relatively small doses of VPA.

RESULTS: Although serum hepatic enzymes, such as AST and ALT, were normal, serum ammonia concentration was high, i.e. 70 micromol/l (normal range 9-33 micromol/l). Administration of VPA was discontinued immediately after admission. The patient's condition improved during the second week of hospitalization and ammonium levels returned to normal.

CONCLUSION: In conclusion, although uncommon, a possible induction of non-convulsive status epilepticus by valproate-induced hyperammonemic encephalopathy should be taken into account and properly managed by discontinuation of the drug.