Proton MR spectroscopy in hyperhomocysteinemia with elevated blood methionine levels.

Proton magnetic resonance spectroscopy imaging (MRSI) and serial MRI were performed on a 10-year-old girl with B6 unresponsive cystathionine B-synthase (CBS) deficiency who developed high methionine levels while on betaine therapy. At presentation, T2-weighted sequences showed diffuse white matter (WM) hyperintensity and sulcal effacement, while MRSI metabolite concentrations were normal. Four months later, after the betaine therapy was discontinued and a methionine-restricted diet with vitamin B6, B12, and folate supplementation was initiated, blood methionine levels and MRI findings returned to normal. Normal MRSI at presentation was predictive of a positive outcome despite the markedly abnormal initial MRI results.