Teaching NeuroImages: MRI findings in carbamoyl phosphate synthetase 1 deficiency

A girl with carbamoyl phosphate synthetase 1 (CPS-1) deficiency, symptomatic since the newborn period, underwent liver transplantation at 7 months. She later developed ataxia and truncal dystonia. MRI brain at age 2 years showed hyperintensities in proton density and fluid-attenuated inversion recovery images involving the insular cortices, deep frontal gyri (figure 1, A and B), caudate nucleus, and putamen (figure 2, A and B). These findings are characteristic of proximal urea cycle disorders, namely CPS-1 deficiency,(1, 2) and are unlikely due to myelinolysis, pontine or extrapontine. The above findings on an MRI in an encephalopathic child give a clue to the diagnosis of a hyperammonemic disorder.