Temporal lobe perfusion on single photon emission computed tomography predicts the rate of cognitive decline in Alzheimer's 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 123I-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 probably 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.