Longitudinal study of cognitive and functional brain changes in ageing and cerebrovascular disease, using proton magnetic resonance spectroscopy

The neurophysiological basis of cognition changes with age is relatively unexplained,with most studies reporting weak relationships between cognition and measures of brainfunction, such as event related potentials, brain size and cerebral blood flow. Protonmagnetic resonance spectroscopy (1H-MRS) is an in vivo method used to detectmetabolites within the brain that are relevant to certain brain processes. Recent studieshave shown that these metabolites, in particular N-acetyl aspartate (NAA), which isassociated with neuronal viability, correlate with performance on neuropsychologicaltests or other measures of cognitive function in patients with a variety of cognitivedisorders associated with ageing and in normal ageing subjects. We have studied therelationship between metabolites and cognitive function in elderly patients 3 months and3 years after a stroke or transient ischemic attack (TIA) and in an ageing comparisongroup. Metabolites were no different between stroke/TIA patients and elderly controls,however, there were significant metabolite differences between stroke/TIA patients withcognitive impairment (Vascular Cognitive Impairment and Vascular Dementia) and thosewithout. Frontal measures of NAA and NAA/Cr predicted cognitive decline over 12months and 3 years in stroke/TIA patients and elderly controls, and these measures weresuperior predictors than structural MRI measures. Longitudinal stability of metabolites inageing over 3 years was associated with stability of cognitive function. The resultsindicate that 1H-MRS is a useful tool in differentiating stroke/TIA patients with andwithout cognitive impairment, with possibly superior predictive ability than structuralMRI for assessing future cognitive decline. The changes in 1H-MRS that occur withageing and cognitive decline have implications for the neurophysiological mechanismsand processes that are occurring in the brain, as well as application to clinical diagnosis,the early detection of pathology and the examination of longitudinal change