This has led to different varieties of MSA receiving different names, depending on which area of the brain has predominant involvement. In patients in whom changes in autonomic function dominates the initial presentation, particularly changes in blood pressure regulation, the MSA form is often called Shy-Drager syndrome. Between 25,000 and 100,000 American have multiple system atrophy. However, many will not receive the correct diagnosis during their lifetime. MSA usually occurs after age 50, with a slightly higher incidence in males.
Patients usually have autonomic nervous system dysfunction first.
In spite of low blood pressure while standing, it is common for MSA patients to have high blood pressure when lying down. A fall in blood pressure following meals or in hot weather or following infection is quite common. When MSA begins with non-autonomic features, imbalance is the most common feature. This difficulty in maintaining balance may be due to either cerebellar or Parkinsonian abnormalities. The concurrent involvement in MSA of multiple brain systems subserving movement, including the striatum, cerebellum, and cortex, leads to the movement disorder as often being the most profound disability.