Management Impact of FDG-PET in Dementia: Results from a Tertiary Center Memory Clinic

BACKGROUND: 2-[18F]fluoro-2-Deoxy-D-glucose (FDG) positron emission tomography (PET) may assist the diagnosis of dementia but it is an expensive investigation. OBJECTIVE: To obtain management impact data for FDG-PET in dementia. METHODS: This was a prospective study of 194 consecutive patients referred from a memory clinic for FDG-PET at the discretion of the dementia specialists. Diagnosis and management plans formulated at a multidisciplinary patient review meeting were compared before and after the release of PET findings. RESULTS: FDG-PET had moderate to high impact on the diagnosis and management in 85 (44%) participants. Diagnosis changed from probable neurodegenerative disease in 27 patients to a non-degenerative diagnosis and vice versa in 12 patients. PET changed the type of dementia in another 29 (15%) participants and prescription of cholinesterase inhibitors in 33 patients (17%). Number of uncertain diagnoses reduced from 58 to 35 (p < 0.001, χ2 = 15.12), differential diagnoses reduced from 127 to 55 (p = 0.003) and very probable diagnoses increased from 5 to 42 (p ≤ 0.001, χ2 = 1.01). Mini-Mental State Examination score was higher in those where PET had high diagnostic impact (26.3 ± 3.1 versus 23.9 ± 5.1, p ≤ 0.05). The degree of impact correlated with the pre-scan level of diagnostic uncertainty (ρ = -0.258, p < 0.001). DISCUSSION: The management impact was higher in those with greater diagnostic uncertainty and in those with less severe cognitive impairment. The findings suggest that FDG-PET is a useful adjunct for the management of suspected dementing disorders in appropriately selected patients.