Global N-Acetylaspartate in Normal Subjects, Mild Cognitive Impairment and Alzheimer's Disease Patients

Background: Mild cognitive impairment (MCI) is an intermediary state on the way to Alzheimer’s disease (AD). Little is known about whole brain concentration of the neuronal marker, N-acetylaspartate (NAA) in MCI patients. Objective: To test the hypothesis that since MCI and AD are both neurodegenerative, quantification of the NAA in their whole brain (WBNAA) could differentiate them from cognitively-intact matched controls. Methods: Proton MR spectroscopy to quantify the WBNAA was applied to 197 subjects (86 females) 72.6 ± 8.4 years old (mean ± standard deviation). Of these, 102 were cognitively intact, 42 diagnosed as MCI, and 53 as probable AD. Their WBNAA amounts were converted into absolute concentration by dividing with the brain volume segmented from the MRI that also yielded the fractional brain volume (fBPV), an atrophy metric. Results: WBNAA concentration of MCI and AD patients (10.5 ± 3.0 and 10.1 ± 2.9 mM) were not significantly different (p = 0.85). They were, however, highly significantly 25–29% lower than the 14.1 ± 2.4 mM of normal matched controls (p