ObjectiveTo evaluate the pattern and severity of autonomic dysfunction in autopsy-confirmed progressive supranuclear palsy (PSP) compared to α-synuclein pathology.MethodsAutopsy-confirmed cases of 14 patients with PSP, 18 with multiple system atrophy (MSA), and 24 with Lewy body disease (LBD) with antemortem autonomic testing were reviewed retrospectively. All patients underwent comprehensive clinical evaluations by a movement disorder specialist, formal autonomic testing, and postmortem examinations at Mayo Clinic.ResultsThe absence of orthostatic hypotension (OH) was the strongest autonomic parameter that distinguished PSP from α-synucleinopathies (0% vs 69%, p < 0.0001). Tests of adrenergic failure, which distinguish neurogenic OH, also differentiated PSP from other groups. These included the pressure recovery time (p = 0.0008), adrenergic impairment score (p = 0.001), and magnitude of change of systolic (p = 0.0002) and diastolic (p = 0.0001) blood pressures (BPs) during upright tilt. In addition, REM sleep behavior disorder was seen less frequently (p = 0.006) in PSP (33%) compared to MSA (87%) and LBD (90%). Antemortem clinical diagnostic accuracy for these phenotypically variable disorders was 57% for PSP and 83% for α-synucleinopathies.ConclusionOur results suggest that the cardiovascular adrenergic system, which sustains BP during standing, is relatively unaffected, if not spared, in PSP. These findings increase our understanding of the clinical signature of PSP and have the potential to improve diagnostic accuracy in atypical parkinsonisms by distinguishing PSP from the α-synucleinopathies.