Positron emission tomography in evaluation of dementia - Regional brain metabolism and long-term outcome

Context Deficits in cerebral glucose utilization have been identified in pa tients with cognitive dysfunction attributed to various disease processes, but their prognostic and diagnostic value remains to be defined. Objective To assess the sensitivity and specificity with which cerebral met abolic patterns at a single point in time forecast subsequent documentation of progressive dementia. Design, Setting, and Patients Positron emission tomography (PET) studies of [F-18]fluorodeoxyglucose in 146 patients undergoing evaluation for dementi a with at least 2 years' follow-up for disease progression at the Universit y of California, Los Angeles, from 1991 to 2000, and PET studies in 138 pat ients undergoing evaluation for dementia at an international consortium of facilities, with histopathological diagnoses an average of 2.9 years later, conducted from 1984 to 2000. Main Outcome Measures Regional distribution of [F-18]fluorodeoxyglucose in each patient, classified by criteria established a priori as positive or ne gative for presence of a progressive neurodegenerative disease in general a nd of Alzheimer disease (AD) specifically, compared with results of longitu dinal or neuropathologic analyses. Results Progressive dementia was detected by PET with a sensitivity of 93% (191/206) and a specificity of 76% (59/78). Among patients with neu ro path ologically based diagnoses, PET identified patients with AD and patients wi th any neurodegenerative disease with a sensitivity of 94% and specificitie s of 73% and 78%, respectively. The negative likelihood ratio of experienci ng a progressive vs nonprogressive course over the several years following a single negative brain PET scan was 0.10 (95% confidence interval, 0.06-0. 16), and the initial pattern of cerebral metabolism was significantly assoc iated with the subsequent course of progression overall (P<.001). Conclusion In patients presenting with cognitive symptoms of dementia, regi onal brain metabolism was a sensitive indicator of AD and of neurodegenerat ive disease in general. A negative PET scan indicated that pathologic progr ession of cognitive impairment during the mean 3-year follow-up was unlikel y to occur.