Objective: We examined the pattern of sweat loss in patients with normal versus abnormal MIBG and considered the implications of this in predicting phenoconversion trajectory.

Background: Normal cardiac metaiodobenzylguanidine (MIBG) scintigraphy and dynamic sweat test (DST)  in pure autonomic failure (PAF) are predictors of phenoconversion towards multiple system atrophy (MSA) rather than parkinson’s disease (PD) or dementia with lewy body (DLB). Both can be abnormal in MSA, especially in later disease, in line with a top-down model of disease. However, no study has evaluated the sequence of peripheral denervation across the cardiovascular and sudomotor domains.

Method: As part of our ongoing natural history study, consecutive patients with an initial diagnosis of PAF were systematically phenotyped and followed longitudinally until phenoconversion or death. Participants underwent cardiovascular autonomic testing, cardiac MIBG, dynamic sweat testing (DST), and thermoregulatory sweat testing (TST).

Results: 24 PAF patients, with a median follow up duration of 5.5 years, underwent both MIBG and sudomotor testing. 4/24 patients (17%) had normal MIBG uptake, of whom 1/4 (25%) had pre-ganglionic sweat loss.  This patient and 2 others (75%) later phenoconverted into MSA, while the remaining patient retained PAF diagnosis. Among the 20/24 (83%) patients with abnormal MIBG uptake, all 20/20 (100%) had evidence of post-ganglionic sudomotor dysfunction, these patients all retained a PAF diagnosis or phenoconverted to PD or DLB.

Conclusion: In PAF patients phenoconverting to MSA, cardiac sympathetic innervation appears to remain preserved even in established peripheral sudomotor denervation, possibly due to differing neuronal vulnerability to alpha synuclein deposition. These findings support a multimodal biological framework for PAF to improve prediction of phenoconversion trajectory across disease stages.

Figure 1

« Back to 2026 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/sudomotor-dysfunction-in-patients-with-normal-and-abnormal-cardiac-mibg/