 - with neurogenic orthostatic hypotension associated with primary autonomic failure Parkinson Disease, Multiple System Atrophy and Pure Autonomic Failure. Orthostatic hypotension will be defined as 20 mmHg decrease in systolic BP or 10 mmHg of diastolic BP within 3 minutes on standing associated with impaired autonomic reflexes determined by autonomic testing in the absence of other identifiable causes Freeman et al., 2011. 