Objective: To describe the fluorodeoxyglucose (FDG) metabolic pattern and clinical features in patients with clinical diagnose of atypical parkinsonism such as Progressive Supranuclear Palsy (PSP), Multiple System Atrophy (MSA) and Frontotemporal Dementia (FTD).

Background: The initial clinical diagnostic accuracy in cases of atypical parkinsonism or parkinson-dementia syndrome is usually low. There is a great need of biomarkers that can increase the clinical diagnostic accuracy. In particular, imaging biomarkers can help in the challenge of diagnostic specificity of clinical entities.

Methods: Medical records of patients with clinical diagnose of atypical parkinsonism and FTD (behavioral) who attended the outpatient clinic of Parkinson’s disease and Cognitive disorders clinic in the last year at CEMIC University Hospital, who received FDG PET study as part of the diagnostic work up, were included in the study. Results of cognitive tests and levodopa response were collected.

Results: There were 12 patients, 3 MSA , 3 PSP and 6 FTD. Mean age was 60.3 years (ys) in MSA patients, 63.6 ys in PSP and 67,8 in FTD. Positive levodopa response (UPDRS >20%) was absent in the majority of patients, except in 1 MSA. Cognitive profile showed cortical and behavioral compromise in FTD, subcortical impairment and behavioral symptoms in PSP as opposed to MSA who presented minor subcortical impairment.

Basal ganglia and thalamic hypometabolism was observed in all PSP and MSA patients, and in only one FTD patient who presented left thalamic hypometabolism. Cerebellar hypometabolism was observed only in MSA patients.

PSP and FTD patients presented cortical hypometabolism, which was observed only in 1 MSA patient. FTD patients presented frontal and temporal cortical hypometabolism in 4 out of 6. This changes were bilateral in 3 patients.

Conclusions: Subcortical basal ganglia and thalamic hypometabolism were more frequently observed in patients with predominant atypical parkinsonism as compared to patients with predominant dementia/behavioral symptoms in the FTD group.

FTD patients presented more frequently compromise of cortical metabolic pattern and less frequently basal ganglia abnormalities.

Positive levodopa response was absent in the majority of patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/fdg-pet-studies-in-the-differential-diagnose-of-atypical-parkinsonism-and-dementia-syndromes/