Objective: We aimed to characterize cardiac MIBG uptake patterns in patients with an initial diagnosis of PAF (iPAF) and assess their role as a prognostic tool in stratifying risk of phenoconversion.

Background:

Cardiac metaiodobenzylguanidine (MIBG) scintigraphy helps distinguish Lewy body disorders (LBD) from multiple system atrophy (MSA). In LBD, cardiac MIBG uptake is reduced due to postganglionic sympathetic denervation, whereas uptake is typically preserved in MSA, reflecting predominantly preganglionic pathology. Abnormal MIBG uptake has been reported in most patients with pure autonomic failure (PAF).

Method: As part of our longitudinal natural history study on PAF, consecutive patients with iPAF underwent prospective clinical and autonomic assessments, including cardiac MIBG scintigraphy. Patients were followed until conversion to LBD or MSA, or to last available follow-up set in 2025.

Results: Among 106 patients with iPAF, 63 (59%) maintained a stable PAF phenotype for at least 3 years. Of these, 62 (98%) showed abnormal MIBG uptake; the only patient with normal uptake was a man under 50 with severe urogenital dysfunction requiring catheterization. Thirty-four patients (32%) converted to LBD (Parkinson’s disease or dementia with Lewy bodies); 33 (97%) had abnormal MIBG uptake up to 9 years before phenoconversion, while one patient had normal uptake without atypical clinical features. Eight patients (8%) converted to MSA, all with normal MIBG uptake prior to conversion. The sole patient with parkinsonian features and no definitive diagnosis after 3 years of follow up also had normal uptake.

Conclusion: In this large iPAF cohort, cardiac MIBG scintigraphy proved highly sensitive in detecting cardiac sympathetic denervation and accurately predicted disease trajectories years before phenoconversion, supporting its clinical utility for risk stratification and counseling in iPAF.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnosing-prodromal-synucleinopathies-what-is-the-role-of-cardiac-mibg-scintigraphy/