Postural hypotension and low R-R interval variability in parkinsonism, spino-cerebellar degeneration, and Shy-Drager syndrome.

Systolic blood pressure, mean R-R interval, and R-R interval variance were studied in patients with Parkinson's disease, spinocerebellar degeneration, and Shy-Drager syndrome. Postural hypotension correlated with anhidrosis (p less than 0.05), indicating sympathetic vasomotor dysfunction. Reduction of R-R interval variance while resting supine correlated with bladder-bowel dysfunction (p less than 0.05), indicating parasympathetic impairment. Reduction of R-R interval variance after postural changes correlated with constipation (p less than 0.005), postural hypotension (p less than 0.05), and anhidrosis (p less than 0.05), indicating both parasympathetic and sympathetic involvement. Dynamic study of the R-R interval provides objective information about autonomic function in neurologic disease.