Use of Accelerometer for Quantification of Neurogenic Orthostatic Hypotension Symptoms

Inclusion Criteria:

* Male and female subjects, age 40-80 years.
* Possible or probable Multiple Systems Atrophy, Pure Autonomic Failure, or Parkinson's disease with neurogenic orthostatic hypotension.
* Neurogenic orthostatic hypotension defined as a ≥ 30 mmHg decrease in systolic blood pressure within 3 minutes of standing associated with impaired autonomic reflexes determined by autonomic testing in the absence of other identifiable causes.
* Patients on treatment for neurogenic orthostatic hypotension with either midodrine or atomoxetine, who have experienced some improvement in their orthostatic symptoms, but still remain symptomatic (Orthostatic hypotension symptom assessment \[OHSA\] score of 1 to 5 while on medication).
* Patients who are able to stay with their caregiver during study participation.
* Able and willing to provide informed consent.

Exclusion Criteria:

* Bedridden, physically disabled, or unable to walk.
* Patients with Orthostatic hypotension symptom assessment (OHSA) score ≥ 6, or orthostatic systolic blood pressure drop ≥ 30 mmHg on their regular treatment.
* Patients taking more than one medication for the treatment of neurogenic orthostatic hypotension (concomitant use of pyridostigmine or fludrocortisone are accepted).
* Pregnancy
* Systemic illnesses known to produce autonomic neuropathy, including but not limited to diabetes mellitus, amyloidosis, monoclonal gammopathies, and autoimmune neuropathies.
* Clinically unstable coronary artery disease (recurrent angina despite medical therapy), or major cardiovascular or neurological event in the past 6 months (myocardial infarction, stroke).
* Concomitant use of anticoagulants.