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

Abstract

Previous magnetic resonance (MR) spectroscopy studies of Alzheimer disease (AD) reporting reduced N-acetyl aspartate (NAA) and increased myo-Inositol (mI) used single voxel techniques, which have limited ability to assess the regional distribution of the metabolite abnormalities. The objective of this study was to determine the regional distribution of NAA and mI alterations in AD by using MR spectroscopic imaging. Fourteen patients with AD and 22 cognitively normal elderly were studied using structural MR imaging and MR spectroscopic imaging. Changes of NAA, mI, and various metabolite ratios were measured in frontal and parietal lobe gray matter (GM) and white matter. This study found: (1) when compared with cognitively normal subjects, AD patients had increased mI and mI/creatine (Cr) ratios primarily in parietal lobe GM, whereas frontal lobe GM and white matter were spared; (2) in the same region where mI was increased, AD patients had also decreased NAA and NAA/Cr ratios, replicating previous findings; (3) however, increased mI or mI/ Cr ratios did not correlate with decreased NAA or NAA/Cr ratios; and (4) using mI/Cr and NAA/Cr together improved sensitivity and specificity to AD from control as compared with NAA/Cr alone. In conclusion, decreased NAA and increased mI in AD are primarily localized in parietal lobe GM regions. However, the NAA and mI changes are not correlated with each other, suggesting that they represent different processes that might help staging of AD. KeywordsAlzheimer disease; short TE 1H magnetic resonance spectroscopic imaging; brain myo-Inositol Reprints: Xiaoping Zhu, MD, PhD, MR Unit, 114M, VA Medical Center/UCSF, 4150 Clement Street, San Francisco, CA 94121 (e-mail: zhupxia@itsa.ucsf.edu).. Sources of Support: Grant sponsor: NIH; Grant numbers: AG10897; AG12435; EB00207; EB00822; EB000766; Grant sponsor: VA Research: MIRECC, REAP. NIH Public Access Author ManuscriptAlzheimer Dis Assoc Disord. Author manuscript; available in PMC 2007 March 13. Published in final edited form as:Alzheimer Dis Assoc Disord. 2006 ; 20(2): 77-85. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptAlzheimer disease (AD) is characterized by accumulation of intraneuronal neurofibrillary tangles and extracellular amyloid plaques, as well as progressive loss of neurons that initially involve the hippocampal formation, temporoparietal cortex, and at later stages other cortical regions. 1-3 Such stereotypical regional spread of pathology may be delineated with imaging techniques, including structural magnetic resonance imaging (MRI), which showed brain tissue loss 4 and functional imaging by positron emission tomography (PET), which demonstrated cerebral glucose hypometabolism in AD. 5 However, neither structural MRI nor PET provides specific measures of neuronal or glial alterations.In vivo 1H magnetic resonance spectroscopy (MRS) has been used to measure levels of brain metabolites, such as N-acetyl aspartate (NAA) and myo-Inositol (mI) in AD. 6 Because NAA is found in relative...

Magnetic resonance spectroscopy reveals abnormalities of glucose metabolism in the Alzheimer's brain

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