Multiple system atrophy.

MSA is a complex disorder, with regard to its pathology and cause as well as its clinical diagnosis and treatment. Although a number of clinical treatments may improve quality of life for these patients, given the widespread pathology present, symptomatic treatment, particularly that involving neurotransmitter replacement, is likely to remain difficult. Truly effective treatment for these patients is likely to depend on an understanding of the underlying pathogenic mechanisms and methods to halt or reverse disease progression. A firm understanding of the classification of these disorders is the first step to understanding the relevant pathogenic mechanisms. The finding of intracytoplasmic glial inclusion bodies provides a compelling piece of evidence that SND, OPCA, and SDS do, in fact, belong to one nosologic entity. These inclusions do not seem to be present in familial cases of OPCA; thus, they may provide a means to improve diagnostic specificity as well as sensitivity. With the ability to define clearly the entity of MSA, an understanding of the pathophysiology can be developed along with other degenerative neurologic diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's disease.