MRI in a case of adult-onset citrullinemia

A 42-year-old man presented with a history of repeated episodes of consciou sness disturbance for 5 years. The MRI showed abnormally high signal intens ities on T2-weighted images at bilateral cingulate gyri, temporal lobes and insular regions, mimicking the finding of herpes simplex encephalitis. Hyp erammonemia was disclosed. Serial work-up led to the diagnosis of adult-ons et citrullinemia, deficiency of argininosuccinate synthetase. The clinical symptoms improved after diet control and medication. Followup MRI showed re solution of the abnormal signal intensities. The MRI findings of citrulline mia and other urea-cycle defects might be attributed to hyperammonemic ence phalopathy, but the manifestations were varied. Similar distribution of the abnormalities in the MRI could be found in some reported cases and indicat es probably vulnerable sites of hyperammonemic brain injury.