Usefulness of magnetic resonance spectroscopy in urea cycle disorders.

Late-onset urea cycle disorders are characterized by chronic encephalopathy and a risk of hyperammonemic crises triggered by environmental stressors. Reported here is the case of a 30-year-old woman with chronic encephalopathy due to argininosuccinate lyase deficiency. Cerebral proton magnetic resonance spectroscopy showed brain creatine deficiency and its normalization during treatment. These findings are in keeping with recent reports suggesting that creatine deficiency is involved in the neurological dysfunction of urea cycle disorders and demonstrate the usefulness of magnetic resonance spectroscopy in the diagnosis and follow-up of urea cycle disorders.