TEMPORAL-LOBE PERFUSION ON SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY PREDICTS THE RATE OF COGNITIVE DECLINE IN ALZHEIMERS-DISEASE

Objective: To examine the ability of relative regional cerebral blood flow as measured by single photon emission computed tomography to predict longitudinal course of cognitive decline in Alzheimer's disease. Design: Single photon emission computed tomography using the blood flow tracer I-123-N-isopropyl-p-iodoamphetamine was performed at initial evaluation and was used to predict the rate of cognitive decline over a follow-up period from 1 to 4 years. Setting: Outpatient university dementia clinic and center for functional imaging. Participants: Twenty-nine patients met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable or possible AD. Results: Temporal lobe regional cerebral blood flow ratio at initial evaluation correlated with rate of decline in Mini-Mental State Examination over the longitudinal follow-up. Temporal regional cerebral blood flow ratio also predicted rate of decline of specific memory measures on the California Verbal Learning Test. Neither parietal nor frontal ratios predicted rate of cognitive decline. Dorsolateral frontal hypoperfusion was associated with the emergence of perseverative behaviors over time. Age, prior dementia duration, estimated prior rate of decline, and initial severity did not predict rate of cognitive decline. Conclusion: Results suggest that regional perfusion on single photon emission computed tomography may predict cognitive decline in Alzheimer's disease better than these demographic and course variables.