Quantitative sudomotor abnormalities in clinically isolated rapid eye movement sleep behavior disorder

Post-ganglionic sudomotor abnormalities are common in Parkinson's disease (PD), however data in clinically isolated REM sleep behavior disorder (iRBD) are limited. To determine the prevalence of sudomotor abnormalities in a cohort of patients with iRBD. We performed a retrospective review of patients seen in our autonomic clinic who underwent testing with the quantitative sudomotor axon reflex test (QSART). We identified three groups for comparison: 1.) iRBD, 2.) PD with RBD (PDwRBD) 3.) PD without RBD (PDwoRBD). PDwRBD (n = 27) patients demonstrated the greatest sudomotor abnormalities (sudomotor CASS 1.44 ± 1.24), followed by PDwoRBD (n = 23, 0.57 ± 0.5) and iRBD (n = 20, 0.55 ± 0.94) (p = 0.015). Twenty percent of patients with iRBD had an abnormal result, compared to 67% PDwRBD and 35% PDwoRBD. Sudomotor abnormalities are common in patients with iRBD, supporting the concept that peripheral autonomic impairment occurs early in the course of disease.