₁H‐MRS, MRI‐Based Hippocampal Volumetry, and ^99mTc‐HMPAO‐SPECT in Normal Aging, Age‐Associated Memory Impairment, and Probable Alzheimer's Disease

Abstract

These findings support the hypothesis of a continuum among the three conditions studied, or at least between AAMI and DAT, where AAMI seems to be an early, monosymptomatic stage of Alzheimer disease. Accepting this view, it would be questionable to maintain the term "age-associated memory impairment" as a discrete entity.

Regional metabolic patterns in mild cognitive impairment and Alzheimer’s disease

“…These data also support the concept that an elevation in MI /Cr is evident prior to the full clinical manifestations of AD. However the criteria used for the diagnosis of age associated memory impairment are different from criteria used in our study for MCI 10 .…”

“…Anatomic neuroimaging studies of MCI patients have been published 23 . Although, biochemical alterations have been shown in the brains of patients with age associated memory impairment 10 , to our knowledge, there are no published data specifically addressing the 1 H MRS findings in MCI patients.…”

“…Although probable AD patients had higher Cho /Cr ratios compared to MCI patients with TE= 30 ms., this difference did not reach statistical significance with TE= 135 ms. To our knowledge, there is no directly comparable published data that addresses 1 H MRS findings in the same group of AD subjects with different echo times in the posterior cingulate gyri. Some studies have found elevated and some comparable or depressed Cho /Cr ratios in AD patients relative to elderly controls [8][9][10][11][12][13][14][15] . The disagreement in the literature on this point may depend not only on the clinical heterogeneity of the patients and sampling of different regions in the brain, but also on the echo times used.…”

“…A recent study with single photon emission tomography (SPECT) showed a decline in blood perfusion in the hippocampal-amygdaloid complex, anterior thalamus and cingulate gyrus in both preclinical and early AD 6 . 1 H magnetic resonance spectroscopy ( 1 H MRS) studies reveal a decrease in N-acetylaspartate (NAA) and an increase in myoinositol (MI) peak contents in the brains of AD patients [7][8][9][10][11][12][13][14][15] . NAA is a neuronal marker and a decrease in its concentration suggests neuronal loss or dysfunction 16,17 .…”

Brain proton magnetic resonance spectroscopy (1H-MRS) in Alzheimer's disease: changes after treatment with xanomeline, an M1 selective cholinergic agonist

“…Also, we did not include age-matched control subjects without Alzheimer's disease, which would have allowed us to test the hypothesis that Alzheimer's disease is associated with higher choline/creatine ratios at baseline. Although some studies have indicated high ratios (4,14), others have not (15,16). MRS was performed by using only a single brain voxel, but a reproducible method was used to standardize its placement and enhance reliability of the metabolite resonances.…”