Correlation of regional proton magnetic resonance spectroscopic metabolic changes with cognitive deficits in mild Alzheimer disease

Context: The staging of Alzheimer disease (AD) dementia could be improved by a neurometabolic analysis using magnetic resonance spectroscopy. Objective: To examine the correlation between regional cerebral metabolic alterations measured by proton magnetic resonance spectroscopy and neuropsychological dysfunctions in patients with early AD. Design: A case-control study. Setting: University hospital neurology clinic and radilyology department. Participants: A cohort of 14 patients with mild AD and 14 control subjects paired for age and sex. Interventions: Single-voxel proton magnetic resonance spectroscopic brain examination (60 minutes) and a comprehensive battery of psychometric tests (2 hours). Main Outcome Measures: Metabolite ratios relative to unsuppressed water were calculated for magnetic resonance spectroscopic metabolites (N-acetylaspartate, choline, creatine-phosphocreatine, and myo-inositol) in the medial temporal lobes (MTLs), parietotemporal cortices (PTCs), and frontal cortices of both hemispheres. Correlations were examined between metabolic changes in an area and psychometric scores of its known regional function: MTL and verbal memory, PTC and language and visuoconstructional abilities, and frontal cortices and executive functions. Results: A significant reduction of N-acetylaspartate/ water (H2O) in the left MTL and of choline/H2O in both MTLs, as well as a significant increase of myo-inositol/ H2O in the right PTC were observed. Metabolic alterations in the left MTL were correlated with a loss of verbal memory, in the left PTC with language impairment, and in the right PTC with a loss of visuoconstructional abilities in the group with AD. Conclusion: These findings are consistent with regional distribution of neuropathologic changes and cognitive symptoms characterizing early phases of AD, and with the pattern of lateralization of normal brain function.