Brain metabolite concentration and dementia severity in Alzheimer's disease - A H-1 MRS study

Objective: H-1-MRS studies have shown abnormalities in brain levels of inyo -inositol (mI) and N-acetyl aspartate (NAA) in AD, but the relation of thes e abnormalities with dementia severity was not examined. The authors sought to determine whether altered brain levels of mI and other metabolites occu r in mild AD and whether they change as dementia severity worsens. Methods: The authors used H-1-MRS with external standards to measure absolute brain concentrations of mI, NAA, total creatine (Cr), and choline (Cho)-containi ng compounds in 21 subjects with AD and 17 age- and sex-matched controls in occipital and left and right parietal regions. Results: Concentrations of NAA were significantly decreased, whereas mI and Cr concentrations were sig nificantly increased in all three brain regions in subjects with AD compare d with controls. Higher concentrations of mI and Cr occurred even in mild A D. A discriminant analysis of the H-1-MRS data combined with CSF volume mea surements distinguished subjects with AD, ranging from mild to severe demen tia, from controls with 100% correct classification. NAA concentration, tho ugh not other metabolites, was positively correlated with Mini-Mental State Examination score. Conclusion: The measurements with H-1-MRS of absolute m etabolite concentrations in the neocortex showed abnormal concentrations of brain metabolites in AD; these metabolite concentrations do not necessaril y correlate with disease severity. Although changes in myo-inositol and cre atine occur in the early stages of AD, abnormalities of N-acetyl aspartate do not occur in mild AD but progressively change with dementia severity. Fu rther, subjects with mild AD can be differentiated from controls with H-1-M RS.