Functional Imaging Predicts Cognitive Decline in Alzheimer's Disease

Eighteen patients with Alzheimer's disease were studied with positron emission tomographic measurements of regional cerebral metabolism of glucose. All patients were initially diagnosed and evaluated, underwent positron emission tomography, and then were followed with annual reevaluations, at which time the Mini-Mental State Examination (MMSE) was performed. Patients were followed for an average of 2.5 years, and the rate of cognitive decline was calculated by determining the rate of change in the MMSE score defined as the MMSE score at the initial evaluation minus the MMSE score at the last examination, divided by the number of months between testing. The regional cerebral metabolic rates for glucose determined at the time of the first MMSE were then regressed on these changes in scores. Results showed that glucose metabolic rates in posterior temporal and primary visual cortex regions were significantly correlated with the subsequent rate of cognitive deterioration. These associations were not confounded by age, length of follow-up, baseline MMSE score, or education. Stratification on gender suggested that these associations were much stronger in women than in men. These results replicate previous findings showing that functional brain imaging is predictive of the rate of cognitive decline in Alzheimer's disease.