Abstract

Purpose: We propose markers for the characteristics of the local metabolic state of the brain in elderly patients (NG), patients with AD(ADG), MCI(MCIG), PD(PDG) and various level of CI.

Methods: All groups of patients are studied by MRI and ¹H MRS with 1.5T Magnetom Sola (SIEMENS). The examined subjects are divided into 5 groups. The 1^st – (NG) includes 21 healthy volunteers (60-75y). The 2^nd – (MCIG) consists of 34 patients (56-84y), disease duration 4-6 y. The 3^rd – (ADG) includes 28 patients (70-91y) with primary AD-dementia (4-7y). The 4^th (PDG) consists of the 1^st sub-group (DPDG) - 13 PD-patients with dementia (MMSE<25), the 2^nd sub-group (CIPDG) - 15 PD-patients with mild CI (30≥MMSE≥25), and 3^rd sub-group (NPDG) - 12 PD-patients with normal cognitive function (MMSE≥30). All spectra are recorded with 2D CSI SE:TR/TE=1500/135, 30 ms; VOI=8x8x2cm³; NS=1. In patients with MCI and clinical suspicion of AD, MRI is used to rule out other form of dementia, such as vascular dementia, and neoplasm. Cerebral atrophy that occurs in patient with AD may be seen on MRI, however, also affects elderly people without AD. In patients with AD, the atrophy has a very characteristic pattern, primarily affecting the hippocampus. Spectra have been analyzed in both hemispheres in the hippocampal areas, in the occipital (gray matter, GM), and frontal lobe (white matter, FL), in the putamen (P), and in the temporoparietal cortex.

Results: From the spectra the content (in mM) of NAA, Cr, Cho, mIns, Glx=Glu+Gln, and the ratios: NAA/Cho, NAA/Cr, Cho/Cr, mIns/Cr, Glx/Cr are obtained. For the NG the NAA content decreased with age, and characteristic value Cho/Cr = 0.82+-0.05. For MCIG and ADG spectral changes are recognized first in the cingulate gyrus followed eventually by changes in the occipital cortex. For ADG we observe the normal mIns content, and normal mIns/Cr ratio, but in posterior portion of cingulate gyrus the mIns/Cr ratio increased (0.80), the MCI and AD spectral abnormalities occur in posterior portion of cingulate gyrus first. We consider the values of mIns/Cr above 0.7 as highly suggestive of AD. A possible explanation is that abnormalities are present in relative number of glial cells when compared with the number of neurons.  For the patients of DPDG the significant decrease of NAA, Cr, and Glx, and increase of Cho, and mIns content in sampled regions are observed. In P the values NAA/Cr ratios in DPDG and CIPDG are significantly lower than in the NPDG, and Cho/Cr ratios higher than in patients of NPDG. Concentration of NAA in P:(6.81+-1.8), (7.62+-1.4), (7.82+-1.3) in DPDG, CIPDG, and NPDG, respectively, and the ratios of NAA/Cr decrease with the grade of CI. Content of mIns in FL: (4.23+-0.79), (3.69+-0.62), (3.43+-0.83) in DPDG, CIPDG, and NPDG, mIns/Cr increase with the grade of CI. For all groups of patients in any regions of the brain there is no dependence between NAA/Cr, Cho/Cr, mIns/Cr ratios and motor disability or disease duration, and CI. Content of Glx in the FL is more pronounced, than other metabolites:(8.1+-1.9), (9.32+-1.6), (10.6+-1.8) in DPDG, CIPDG, and NPDG, respectively, and Glx/Cr decrease with the grade of CI.

Conclusion: ¹H MRS may provide additional information in the differential diagnosis of MCI, AD and PD with various level of CI. Content of Glx in FL, and in P is indicator of neuronal loss and dysfunction, and may be useful putative biomarker of CI in patients with PD. increasing prevalence of AD in elderly patients.