Proton magnetic resonance spectroscopy can differentiate Alzheimer's disease from normal aging

In order to evaluate the pattern of proton magnetic resonance spectroscopy (1H-MRS) in the gray and white matter of patients with Alzheimer's disease (AD) and healthy controls, a cross-sectional study was carried out on 13 consecutive AD patients and 7 healthy older subjects who were referred to the Day-Hospital for diagnostic assessment. All examinations were performed on a 1.5 Tesla whole-body scanner. Volumes of interest were selected in both the gray (temporal region) and the white (frontal region) matter. N-acetyl group, total creatine, total choline and myo-inositol were quantified referring the metabolite peak area to the unsuppressed water peak area acquired under the same conditions, and the ratio was expressed in arbitrary units. A significant decrease in N-acetyl-aspartate (NAA) in both gray and white matter and an increase in myo-inositol (mI) in gray matter of AD patients were observed. The gray matter NAA/mI ratio clearly separated the two groups. White matter mI was significantly associated with severity and duration of dementia. No association with age was documented. It can be concluded that in vivo 1H-MRS can contribute to the knowledge of pathophysiology of AD, giving neurochemical details of both gray and white matter. In particular, the gray matter NAA/ml ratio seems to be able to differentiate normal cerebral aging from Alzheimer's disease.