Measurement of temporal regional cerebral perfusion with single-photon emission tomography predicts rate of decline in language function and survivalin early Alzheimer's disease

We determined the relationship between regional cerebral blood flow (rCBF) measured with single-photon emission tomography (SPET) and decline in cogni tive function and survival in Alzheimer's disease. In a prospective follow- up study, 69 consecutively referred patients with early probable Alzheimer' s disease (NI-NCDS/ADRDA criteria) underwent SPET performed at the time of initial diagnosis using technetium-99m-labelled hexamethylpropylene amine o xime. Neuropsychological function was assessed at baseline and after 6 mont hs and survival data were available on all patients, extending to 5.5 years of follow-up. Lower left temporal (P < 0.01) and lower left parietal (P < 0.01) rCBF were statistically significantly related to decline in language function after 6 months. The association between left temporal rCBF and sur vival was also statistically significant (P < 0.05) using Cox proportional hazards regression analysis. Performing analysis with quartiles of the dist ribution, we found a threshold effect for low left temporal rCBF (rCBF < 73 .7%, P < 0.01) and high risk of mortality, In this lowest quartile, median survival time was 2.7 years (follow-up to 5.2 years), compared with 4.4 yea rs in the other quartiles (follow-up to 5.5 years). Kaplan-Meier survival c urves showed statistically significant (P < 0.05, log rank test) survival c urves for the lowest versus other quartiles of left temporal rCBF All resul ts were unaffected by adjustment for age, sex, dementia severity, duration of symptoms, education and ratings of local cortical atrophy. We conclude t hat left temporal rCBF predicts decline in language function and survival i n patients with early probable Alzheimer's disease, with a threshold effect of low rCBF and high risk of mortality.