Role of [18F]-FDG PET in patients with atypical parkinsonism associated with dementia

Purpose The present review aims to discuss indications for the use of [F-18]-FDG PET in patients with APS associated with dementia as emerged in the EANM/EAN joint recommendations for its use in dementia. New lines of evidence emerged after the EANM/EAN consensus have here been systematically reviewed. Methods We searched in the databases PubMed, PMC, Google Scholar, Medline using as text "positron emission tomography-PET", "PET/CT", "MR" and "Parkinsonian Syndromes", "Atypical Parkinsonism", "progressive supranuclear palsy", "cortico-basal syndrome", "dementia with Lewy Bodies". We selected only PET studies or multimodal imaging studies including the use of [F-18]-FDG PET. Results Atypical parkinsonian syndromes (APS) associated with dementia are complex clinical scenarios including progressive supranuclear palsy (PSP), corticobasal syndrome/degeneration (CBS/CBD) and dementia with Lewy bodies (DLB). The clinical diagnosis of these diseases is often challenging and has relevant repercussions for patients' management and prognosis. A systematic review of the articles published between December 2015 and December 2019 (so after the deadline of the literature search at the time of the EAN/EANM recommendations) was carried out. A total of further 18 papers met our inclusion criteria. Conclusion Although available studies in patients with APS and dementia suffer from methodological limitations, the expert consensus emerged from the EANM/EAN recommendations was in favor of its use for specific clinical questions in these group of patients. Studies in a larger number of patients published after the publication of the joint recommendations have further supported the use of F-18-FDG PET in patients with APS associated with dementia.