PROTON MAGNETIC-RESONANCE SPECTROSCOPY IN DEMENTIA OF ALZHEIMER-TYPE

Reduced N-acetyl aspartate (NAA) and increased myo-inositol (MI) level s have been reported in patients with dementia of Alzheimer type (DAT) in comparison with controls. We wished to assess the validity of thes e findings and to evaluate possible correlations of metabolite proport ions with cognitive dysfunction in DAT. Twelve patients with DAT and 1 0 healthy age-matched controls were included. The severity of dementia was assessed using different scales including the Mini-Mental State E xamination. MRS was performed with a conventional 1.5 Tesla scanner in a single voxel in the centrum semi-ovale (TE = 30 ms or TE = 136 ms; TR = 1500 ms). The evaluation of MRS results was limited by low interr ater, intermeasurement (different echo times) and test-retest reliabil ities, by a high interindividual variance and by the failure to measur e absolute metabolite concentrations. These problems in mind, it was r emarkable that previously reported reductions of NAA levels in patient s with DAT could be reproduced in the present sample. The proportion o f NAA was diminished in demented subjects in comparison with controls (37% vs 44.90%; short TE). A non-significant trend towards minor reduc tions of creatine, choline and MI proportions in these subjects might indicate that proportions of other metabolites necessarily increase wh en NAA is reduced. Cognitive dysfunction of demented subjects was sign ificantly correlated with reductions of NAA, but not with increases of MI. Due to the present technical and methodological problems and to t he non-specificity of findings, proton MRS cannot be applied to suppor t the diagnosis of DAT in a clinical setting. ((C) 1997 by John Wiley & Sons, Ltd.)