Abnormalities of the brain in nonketotic hyperglycinemia: MR manifestations.

MR imaging in seven patients (4 days to 38 months old) with nonketotic hyperglycinemia showed age-related findings of progressive atrophy and delayed myelination. Parenchymal volume loss was found as early as 4 days after birth and increased in severity with increasing age to 27 months. Both supratentorial and infratentorial volume loss were present in the most severely affected patients. The corpus callosum was abnormally thin in all patients. The state of myelination of the CNS was assessed on T2-weighted images. Decreased or absent myelination within supratentorial white-matter tracts was detected in all four patients 10 months of age or older. Myelination of the brainstem and cerebellum progressed normally. No correlation was found between the degree of volume loss or abnormality of myelination demonstrated by MR and the concentration of glycine in the CSF or plasma. Abnormalities shown by MR correlate well with known pathologic findings in patients with nonketotic hyperglycinemia.