Citrullinemia presenting as uncontrollable epilepsy

We report the case of a 16-year-old girl with a variant form of citrullinemia who had been treated with anticonvulsants for uncontrolled epilepsy during the last 4 years. The diagnosis of citrullinemia was made because she had elevated values for serum citrulline (about 10 times control levels), elevated blood ammonia (over 400 micrograms/dl) and reduced activity of argininosuccinate synthetase in the biopsied liver tissue. Her EEG showed high voltage slow activity, but not triphasic waves, when she had high concentrations of blood ammonia. Treatment with a low-protein diet and sodium benzoate resulted in a normalized blood ammonia level, but her plasma citrulline levels remained unchanged. After the therapy she had neither convulsions nor seizure discharges on EEG, even when all anticonvulsant drug therapy was stopped. Thus it is suggested that hyperammonemia may account for the observed abnormal EEG findings, and triphasic waves on EEG are not always recorded in cases of hyperammonemia.