Longitudinal Magnetic Resonance Spectroscopy as Marker of Cognitive Deterioration in Mild Cognitive Impairment

Abstract

Objective: Amnestic mild cognitive impairment (MCI) is highly predictive of Alzheimer’s disease but the pace of deterioration varies across patients. We hypothesize that magnetic resonance spectroscopy (MRS) could be a useful surrogate marker to monitor progression of cognitive impairment in patients with amnestic MCI. Methods. A cohort of patients with amnestic MCI underwent single-voxel 1H-MRS at baseline and at 2-year follow-up. We included 16 patients who converted to dementia of Alzheimer type and other 16 who did not. Changes in cognitive function were compared with the changes in the metabolite levels assessed in vivo. Results. At baseline the converters had lower mean N-acetyl-aspartate (NAA)/creatine (Cr) ratios in the posteromedial parietal cortex (1.41) than nonconverters (1.47). Most patients tended to lose points in the Mini-Mental test after 2-year follow-up in parallel with decreases in NAA levels ( r = .53; P = .002) in the posteromedial parietal cortex as well. The converters showed significant decreases in NAA levels and Cr ratios, whereas the nonconverters did not ( P = .001 and .02, respectively) in this area. Conclusion. We conclude that MRS is a technique sensitive enough to monitor cognitive changes and progression to dementia in patients with amnestic MCI.