Cardiovascular reflex testing contributes to clinical evaluation and differential diagnosis of Parkinsonian syndromes

The differentiation between Parkinson's disease (PD). progressive supranucl ear palsy (PSP), and multiple system atrophy (MSA) may be difficult but is important for prognostic and therapeutic purposes. Varying degrees of auton omic failure have been described in PD and MSA, whereas its involvement in PSP remains controversial. The aim of this study was to investigate autonom ic function in patients fulfilling strict clinical diagnostic criteria for the disorders;above, to evaluate the diagnostic capacity of laboratory auto nomic rests. The study group was consecutively recruited among patients ref erred to a movement disorder unit. Thirty-four patients with PD, 15 patient s with PSP, and 47 patients with MSA were compared with 18 healthy age-matc hed controls. Autonomic tests included analysis of heart rate variability ( HRV) in temporal domain, at rest and during forced respiration, as well as blood pressure (BP) changes during 75 degrees head-up tilt. HRV did not differ between groups during quiet breathing but was significan tly reduced during forced respiration in MSA (P < 0.01), while PD and PSP g roups did not differ from controls. Hypotensive responses during orthostati c provocation were seen in PD (P < 0.01) and MSA (P < 0.001), whereas BP re mained stable in most PSP patients, not differing from the healthy control group. On an individual basis, decreased HRV and severe hypotensive respons es were seen in MSA patients regardless of age and disease duration, wherea s PD patients showed this combination only at high age and long duration. I n PSP, only a few cases with decreased HRV and limited hypotensive response s were found. We conclude that cardiovascular reflex tests can supplement t he clinical differentiation of Parkinsonian syndromes. <(c)> 2001 Movement Disorder Society.