MRI and 1H-MRS findings in early-onset cobalamin C/D defect

Cobalamin C/D defect is an inborn error of cobalamin metabolism causing methylmalonic aciduria and homocystinuria. The early-onset form is characterized by severe neurological impairment. The aim of this study was to evaluate and monitor brain damage in early-onset cbl-C/D defect by conventional MRI and to assess the additional value of 1H-MRS.

We retrospectively examined serial MRI studies of 7 patients, performed on a 1.5 T system. Four patients had the first evaluation within the first 4 months of life and three later. The imaging protocol included spin-echo T1-weighted, T2-weighted, IR, and FLAIR. Five patients underwent 1H-MRS, using chemical shift imaging (CSI) in three patients and single voxel spectroscopy (SVS) in two.

Three of the patients studied early showed tetraventricular hydrocephalus and diffuse swelling of supratentorial white matter with involvement of the "U" fibres. Two showed patchy cavitating lesions in the basal ganglia. White matter changes became evident at a later stage. In three cases 1H-MRS showed an abnormal peak of lactate in the basal ganglia or in the periventricular white matter.

Our study shows severe heterogeneous brain MR abnormalities in cbl-C/D defect. We observed unusual basal ganglia lesions in 30 % of our cases and also found a high incidence of hydrocephalus and supratentorial white matter abnormalities.