To determine whether MR-Spectroscopy (MRS) can be used to assess Alzheimer’s disease (AD) patients. To determine whether there is significant variation in metabolic ratios in the left hippocampus (LH) and in the posterior cingulate gyri (PCG). To confirm the ability of MRS in detecting metabolites changes in early phases of dementia.
METHOD AND MATERIALS
We studied 62 patients (28men, 34women; mean age67.4y, MMSE6-21) who met the NINCDS-ADRDA criteria for clinically probable AD and 30 healthy control subjects (18men, 12women; mean age63.3y, MMSE>28) without dementia. All subjects were submitted to MR exams using a MR standard protocol and MRS on a 1.5T clinical scanner. MRS studies were performed using a single-voxel technique with PRESS sequence (TE 30 ms) in the PCG and in the LH. 24 patients with probable AD were excluded from our study: diagnosis of diabetes mellitus (n=7); stroke (n=2) and technical difficulties (n=15). NAA/Cr and mI/Cr ratios were analyzed for each subject in the PCG and in the LH.
Significant increase of mI/Cr(mean0.84) and decrease of NAA/Cr(mean1.59) in the LH were found in probable AD patients when compared with healthy controls subjects (respectively 0.67 and 1.87). Significant increase in mI/Cr(mean0.71) and decrease in NAA/Cr(mean1.66) at PGC were also noted. The mI/Cr ratio was increased in 31(81.57%) patients in the LH(0.91) and 24(63.15%) in the PGC(0.75). 10 (26.31%) patients had the mI/Cr ratio increased only in the LH(0.87) and 2(5.2%) only in the PGC(0.84). 21(55.26%) patients had the mI/Cr ratio increased in both the LH(0.81) and PCG(0.74). NAA/Cr ratio was decreased in 14(36.84%) patients only in the LH(1.45), in 3 patients in the PGC(1.49) and in 8(21.05%) in both localizations (1.48 LH, 1.51 PGC). 5(13.15%) patients had normal MRS analysis.
MRS can be used as an efficient tool to assess probable AD patients, by increase mI/Cr and decrease NAA/Cr. MRS may provide valuable information about pathophysiological progression of disease, as hippocampus alterations precedes findings in the PCG. The advent of new MR technical facilities provided better local magnetic field homogeneity and, therefore, a better quality of MRS of the hippocampus.