Cerebral [18F]FDG PET in the diagnosis of Atypical Parkinson Disease

Background: Atypical parkinsonian disease (APD) often present with Parkinson symptoms bu have a much poorer long-term prognosis. such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), corticobasal disease (CBD) and Lewy body dementia (DLB). The diagnosis is presently based on clinical features but a cerebral PET scan with [18F]fluoro-2-deoxy-2-D-glucose ([18F]FDG) is part of European guidelines for the differentiation between the subtypes of APD. However, only few studies have evaluated the sensitivity and specificity of [18F]FDG PET in a mixed patient population in differential diagnosis of APD.
Purpose: We aim to measure the sensitivity and specificity of [18F]FDG PET in differential diagnosis of atypical parkinsonism in a retrospective material. .
Material and methods: We identified 170 who were referred for a cerebral [18F]FDG PET at Bispebjerg Hospital for suspicion of APD during January 1st 2017 and December 30th 2019. The study was approved by the Danish Patient Safety Authority (31-1521-255) and by the Danish Data Protection Agency (P-2020-530).
The [18F]FDG PET was analyzed using SyngoVia (Siemens-Healthineers, Scenium) by a nuclear medicine specialist with experience in neuroimaging and blinded to clinical information. The reference standard was the follow-up clinical diagnosis.
Preliminary results: In the first 40 patients, the median follow-up time to diagnosis or death was 31 months (range: 11-72). The overall accuracy in the study was 75%. Classification sensitivity, specificity, positive and negative predictive values for MSA (n=8), DLB (n=6), and CBD/PSP (n=26) respectively, were 100%, 94%, 80% and 100% for MSA, 83%, 97%, 83% and 97% for DLB and 65%, 100%, 100% and 61% for CBD/PSP.
Conclusion Our preliminary results support the use of [18F]FDG PET for the clinical diagnosis of APD with high sensitivity and specificity. Early use of [18F]FDG PET may result in earlier diagnosis, which is beneficial for prognosis and supportive treatment of the patients. No disease modifying treatment is presently available for APD, and the high specificity of [18F]FDG PET may be beneficial in the selection of patients for future treatment studies.