Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Dementias

Abstract

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect.Major causes of dementia include Alzheimer's disease (AD) and vascular dementia and less commonly frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, and Huntington's disease. 1-6 Consensus clinical criteria have been proposed and applied for diagnosis of different dementias, but according to pathologic findings, the sensitivity and specificity of these criteria are variable (34%-97%). 7 Even histopathologic examination cannot definitely determine the underlying cause of dementia for individual subjects owing to a high frequency of mixed pathology in the brain of demented patients. 8 Identification of specific diagnostic markers for each dementia is mandatory for early detection of the disease, improving patient management, and evaluation of therapeutic response and disease progression, but this goal remains elusive. 9,10 In vivo structural changes of demented brains have been studied using magnetic resonance imaging (MRI) with increasing frequency. 11-13 Magnetic resonance imaging can provide detailed anatomic information in multiple imaging sections with excellent tissue contrast and spatial resolution. There is no ionized radiation with the MRI technique, which makes it the modality of choice for repeated measurements in longitudinal studies. Improved MRI pulse sequences now provide information concerning tissue characteristics, water diffusion, and perfusion in addition to anatomic structures. Furthermore, cerebral metabolites can be measured in vivo using magnetic resonance spectroscopy (MRS) during the same examination. 14 Changes in different metabolites reflect underlying brain pathology in dementia. 15-17 There are several published reviews of MRI 11-13 and MRS 15-18 relevant mainly to AD; the goal of this article is to review thoroughly recent advances of MRI and MRS in not only AD but also other neurodegenerative dementias and vascular dementia.

Fatores de risco cardiovascular, declínio cognitivo e alterações cerebrais detectadas através de técnicas de neuroimagem

“…A aplicação de técnicas de neuroimagem tem possibilitado investigar a presença de alterações cerebrais in vivo em amostras de portadores de transtornos neuropsiquiátricos comparados a grupos controle de voluntários saudáveis pareados para variáveis demográficas, com qualidade crescente de sensibilidade e resolução anatômica (Hsu et al, 2001). Técnicas como a tomografia computadorizada (TC) e a RM fornecem dados sobre a anatomia estrutural do cérebro, permitindo a detecção de lesões circunscritas ou difusas, ou a avaliação quantitativa do volume de diferentes estruturas cerebrais.…”

Biomarkers of neurodegenerative disorders: How good are they?

“…The number of CAG repeats, as one study showed, may aid in the prediction of age of onset and penetrance of HD [81]. For instance, for a 41-year-old individual who has 42 CAG repeats, it predicts a 91 % chance that the individual will have HD onset by the age of 65 [82]. Onset of the disease may be different but usually comes up in midlife, depending on both sex and age.…”

“…Imaging technologies offer great promise in identifying biomarkers. These modalities include PET and nuclear magnetic resonance spectroscopy (NMRS) [82,83]. Animal and human studies of biomarkers should be run in parallel and compared with each other in order to take advantage of advances being made in animal models to understand the mechanisms of disease.…”

Effects of Alzheimer Disease on Fronto-parietal Brain N-acetyl Aspartate and Myo-Inositol Using Magnetic Resonance Spectroscopic Imaging

“…8,9 Many single voxel (SV) MRS and multivoxel magnetic resonance spectroscopic imaging (MRSI) studies have shown reduced NAA in AD, especially in hippocampus and parietal lobe, with lesser reductions in frontal lobe. 10,11 mI has been suggested as a glial marker 12,13 and, in contrast to NAA, is increased in AD. 14,15 Many SV MRS studies showed increased mI 16-23 associated with decreased NAA [16][17][18][19][20][23][24][25][26] in AD.…”