Comprehensive autonomic assessment does not differentiate between Parkinson's disease, multiple system atrophy and progressive supranuclear palsy

Differential diagnosis of parkinsonian syndromes is a major challenge in movement disorders. Dysautonomia is a common feature but may vary in clinical severity and onset. The study attempted to find a pattern of autonomic abnormalities discriminative for patients with different parkinsonian syndromes. The cross-sectional study included 38 patients with multiple system atrophy (MSA), 32 patients with progressive supranuclear palsy (PSP), 26 patients with idiopathic Parkinson's disease (IPD) and 27 age-matched healthy controls. Autonomic symptoms were evaluated by a standardized questionnaire. The performance of patients and controls was compared on five autonomic function tests: deep breathing, Valsalva manoeuvre, tilt-table testing, sympathetic skin response, pupillography, and 24-h ambulatory blood pressure monitoring (ABPM). Disease severity was significantly lower in IPD than PSP and MSA. Except for pupillography, none of the laboratory autonomic tests distinguished one patient group from the other alone or in combination. The same was observed on the questionnaire. Receiver operating characteristic curve revealed discriminating performance of pupil diameter in darkness and nocturnal blood pressure change. The composite score of urogenital and vasomotor domains significantly distinguished MSA from IPD patients but not from PSP. Our study supports the observation that even mild IPD is frequently indistinguishable from more severe MSA and PSP. Thus, clinical combination of motor and non-motor symptoms does not exclusively point at MSA. Pupillography, ABPM and the questionnaire may assist in delineating the three syndromes when applied in combination.