INTRODUCTION: Autonomic dysfunction (AD) can be a feature of both multiple 
system atrophy (MSA) and idiopathic Parkinson's disease (IPD), conditions that 
are frequently misdiagnosed in life. Most studies on AD in MSA and IPD are based 
on clinical cases without pathological verification.
MATERIAL AND METHODS: We retrospectively analysed AD in 135 pathologically 
confirmed cases of IPD and in 33 of MSA from the UK PD Society Brain Bank.
RESULTS: MSA started at a younger age than IPD (54.4 +/- 10.7 yrs versus 60.6 
+/- 10.8 yrs), and AD began earlier in the course of the illness All MSA 
patients had some degree of AD in life whereas AD was absent in 24% of IPD 
patients. Although each of five autonomic domains was affected in variable 
numbers of IPD patients, AD in MSA generally involved more autonomic domains 
than in IPD, and to a more severe degree, in particular with regard to 
inspiratory stridor.
CONCLUSIONS: These results indicate that the presence of autonomic disturbance 
alone does not distinguish between MSA and IPD in individual cases. However, the 
presence of severe AD, of AD preceding parkinsonism, or of inspiratory stridor, 
are all individually suggestive of MSA.