Objective: The aim of this study was to evaluate the brain magnetic resonance imaging (MRI) findings and ¹⁸F-FDG positron emission tomography/magnetic resonance imaging (PET/MRI) hypometabolism patterns across subtypes of Parkinson-plus syndromes and to determine the distribution of imaging findings across diagnostic groups.

Background: Despite the complementary nature of structural and metabolic imaging, the degree of concordance between MRI and PET/MRI hypometabolism patterns in Parkinson-plus syndromes and related dementias remains unclear.

Method: Patients with neurodegenerative disorders were included in the study.The diagnoses were established according to criteria reported in the literature.Patients were grouped as FTD (with or without amyotrophic lateral sclerosis [ALS]), dementia with Lewy bodies (DLB), corticobasal syndrome (CBS), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). Atrophic regions on MRI were decoded from coded data and classified as frontal, temporal, parietal, occipital, cerebellar, brainstem, and diffuse cerebral atrophy. Regions showing hypometabolism on PET/MRI were identified.

Results: In the diagnostic distribution, Alzheimer’s disease (AD) was the most frequent diagnosis (n = 31), followed by FTD (n = 11), DLB (n = 9), and MSA (n = 7). CBS (n = 3), PSP (n = 3), and ALS (n = 2) were observed less frequently. 

On brain MRI, the most common pattern was diffuse cerebral atrophy (n = 14).

On PET/MRI, hypometabolism was most frequently detected in the temporal lobe (n = 52), followed by the parietal (n = 45) and frontal lobes (n = 42). Occipital (n = 25) and cerebellar (n = 23) hypometabolism were less frequent. Hypometabolism patterns were mostly observed as widespread involvement affecting multiple cortical areas.

Regional involvement patterns were temporoparietal-predominant hypometabolism in AD; frontal and temporal-predominant in FTD; and widespread cortical hypometabolism with occipital involvement in DLB. In MSA and PSP cases, heterogeneous patterns with accompanying cerebellar and brainstem involvement were observed.

Conclusion: In Parkinson-plus syndromes and related dementia subtypes, ¹⁸F-FDG PET/MRI reveals disease-specific metabolic patterns and contributes to differential diagnosis. When evaluated alongside MRI, FDG PET/MRI emerges as a complementary imaging modality that enhances diagnostic reliability.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/regional-distribution-and-concordance-of-structural-mri-and-18f-fdg-pet-mri-findings-in-parkinson-plus-syndromes/