Differences in skin sympathetic involvements between two chronic autonomic disorders: multiple system atrophy and pure autonomic failure.

ABSTRACT

OBJECTIVE: Certain stimuli evoke increased sweat secretion (sympathetic sweat response; SSwR) and reduced skin blood flow (skin vasomotor reflex; SkVR) in the palm/sole. We evaluated SSwR and SkVR in patients with multiple system atrophy (MSA) and pure autonomic failure (PAF). METHODS: SSwR and SkVR on the palm in response to deep inspiration and mental arithmetic were recorded in 11 MSA patients, 11 PAF patients, and 11 healthy controls. In addition, the head-up tilt test was performed, and the coefficient of variation of R-R intervals (CV(R-R)) was obtained. RESULTS: SSwR amplitudes were significantly lower in the MSA and PAF patients than the controls. SkVR amplitudes in the PAF patients were significantly lower than the controls, but preserved in the MSA patients. In head-up tilt tests, all MSA and PAF patients showed orthostatic hypotension, with similar severity. CV(R-R) was low in the MSA and PAF patients, but a significant difference was found only between the PAF and control groups. CONCLUSION: In the MSA patients, SkVR was preserved, but SSwR was diminished. In the PAF patients, both SkVR and SSwR were attenuated. The combination of SkVR and SSwR tests may differentiate MSA and PAF.