Fig 2. Single-voxel proton spectroscopy (¹H-MRS) and whole-brain phosphorous spectroscopy (³¹P-MRS) of patient 2, before (A and B) and after (C and D) 6 months of therapy with Cr at 400 mg/kg/bw/day and guanidinoacetate (GAA)-lowering diet restrictions.

The baseline studies demonstrate, besides a strong reduction of tCr and PCr peaks, an abnormal peak of guanidinoacetate (GAA) at 3.8 ppm on proton spectrum (A), of GAA-phosphate (GAA-P) at –0.5 ppm on phosphorous spectrum (B), and a high level of brain ATP. In contrast, in the on-therapy spectra, the GAA and GAA-P peak are not resolved, ATP turns to normal but there is an incomplete recovery of the tCr and PCr signal intensity.