Regional metabolite concentrations in human brain as determined by quantitative localized proton MRS.

The regional distribution of brain metabolites was studied in several cortical white and gray matter areas, cerebellum, and thalamus of young adults with use of quantitative single-voxel proton MRS at 2.0 T. Whereas the neuronal compound N-acetylaspartate is distributed homogeneously throughout the brain, N-acetylaspartylglutamate increases caudally and exhibits higher concentrations in white matter than in gray matter. Creatine, myo-inositol, glutamate, and glutamine are less concentrated in cortical white matter than in gray matter. The highest creatine levels are found in cerebellum, parallel to the distribution of creatine kinase and energy-requiring processes in the brain. Also myo-inositol has highest concentrations in the cerebellum. Choline-containing compounds exhibit a marked regional variability with again highest concentrations in cerebellum and lowest levels and a strong caudally decreasing gradient in gray matter. The present findings neither support a metabolic gender difference (except for a 1.3-fold higher myo-inositol level in parietal white matter of female subjects) nor a metabolic hemispheric asymmetry.