Abstract
IntroductionStudies have reported autonomic impairment in patients with idiopathic REM sleep behaviour disorder (iRBD), which is considered a prodromal stage of alpha-synucleinopathies. It is still debated whether central or peripheral pathologies are first manifestations of alpha-synucleinopathies. This study aimed to characterize autonomic and somatosensory function in iRBD patients.MethodsThis cross-sectional prospective case–control study included 17 iRBD patients (mean age 66.3 ± 9.2 years) and 16 healthy controls (HCs, 66.6 ± 11.3 years). Quantitative sensory testing, neurological and neuropsychological assessments, norepinephrine blood plasma levels, tilt table examination with orthostatic blood pressure, and heart rate variability were carried out. Longitudinal data of 10 iRBD patients, including neurological, neuropsychological, and tilt table examination, were assessed.ResultsiRBD patients more frequently presented with orthostatic dysfunction than HCs (70.6% vs. 6.3%, p < 0.0001). Supine norepinephrine plasma levels were normal, but lower in iRBD (249.59 ± 99.78 pg/ml iRBD, 354.13 ± 116.38 pg/ml HCs, p < 0.05). Quantitative sensory testing revealed impaired cold (CDT) and vibration detection thresholds (VDT) on the foot in iRBD (CDT foot iRBD − 1.24 ± 0.31, HCs − 9.89E-17 ± 0.25, VDT iRBD − 1.11 ± 0.47, HCs − 1.46E-16 ± 0.25, p < 0.05). Cold detection thresholds differed between the foot and hand among iRBD patients (foot − 1.24 ± 0.31, hand − 0.56 ± 0.25, p < 0.05). Longitudinal data revealed an increase in maximum systolic and diastolic orthostatic blood pressure changes and a decrease in the Valsalva ratio in the follow-up group (p < 0.05).ConclusionThis study revealed autonomic dysfunction with somatosensory impairment, and decreased norepinephrine levels in iRBD, which may serve as a possible prodromal marker for developing alpha-synucleinopathy.
Highlights
Studies have reported autonomic impairment in patients with idiopathic REM sleep behaviour disorder, which is considered a prodromal stage of alpha-synucleinopathies
In nine idiopathic REM sleep behaviour disorder (iRBD) patients, cranial MRI scans were able to be performed without any signs of structural abnormalities
This study demonstrates autonomic dysfunction in the form of somatosensory impairment and decreased supine NE levels in iRBD patients compared to those in healthy control (HC)
Summary
Studies have reported autonomic impairment in patients with idiopathic REM sleep behaviour disorder (iRBD), which is considered a prodromal stage of alpha-synucleinopathies. It is still debated whether central or peripheral pathologies are first manifestations of alpha-synucleinopathies. Quantitative sensory testing, neurological and neuropsychological assessments, norepinephrine blood plasma levels, tilt table examination with orthostatic blood pressure, and heart rate variability were carried out. Conclusion This study revealed autonomic dysfunction with somatosensory impairment, and decreased norepinephrine levels in iRBD, which may serve as a possible prodromal marker for developing alpha-synucleinopathy. We characterized peripheral autonomic and somatosensory functions in iRBD by means of noninvasive quantitative sensory testing (QST), norepinephrine (NE) blood plasma levels, orthostatic BP, and heart rate changes
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