Valproate-induced hyperammonemic encephalopathy in neurosurgical patients: Our experience and systematic literature review

Sodium valproate is used for the management of seizures, status epilepticus, chronic pain syndrome, bipolar, and other affective disorders. Even with an acceptable safety profile, severe idiosyncratic reactions can occur with valproate use. A rare, serious, and life-threatening side effect of valproate is valproate-induced hyperammonemic encephalopathy (VHE). We intend to analyze the clinical presentation, diagnosis, treatment options, and outcome of VHE in neurosurgical patients and review the pertinent literature on this rare sequelae. We retrospectively reviewed patients who developed VHE following valproate use, either for the treatment of epilepsy or for seizure prophylaxis in our centre. We analyzed the demographic details, clinical presentation, diagnosis, management, and outcomes. A total of four patients with a mean age of 26.3 ± 5.1 (range 19 - 32 years). Valproate was prescribed for primary seizure prophylaxis in 2 patients (50%). The commonest etiology for valproate prescription was for brain tumors (3, 75%) followed by drug-refractory epilepsy (DRE) (1, 25%). None of the patients were documented to have urea cycle disorder. The mean daily prescribed dosage of valproate was 1250 ± 559 mg and the mean duration of administration was 13 ± 13.3 months (range 4 months - 36 months). The mean serum NH3 level was 136,5 ± 44.2 µmol/L (range 107 - 212.8) and all patients (4, 100%) had hyperammonemia with a mortality rate of 50% (2 patients). The hyperammonemia was treated by stopping the valproate use (4, 100%) and dialysis (2, 50%). Normalization of ammonia levels led to clinical improvement in 50% (2 patients). Neurological deterioration in the postoperative period is a diagnostic challenge. VHE is a rare and life-threatening sequelae of Valproate-associated Hyperammonemia (VAH) in neurosurgical patients. A high index of suspicion is required due to its ambiguous presentation. Early diagnosis and prompt treatment can change the course of this life-threatening sequelae.