Primary Autonomic Failure: Three Clinical Presentations of One Disease?

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Three neurodegenerative diseases of unknown cause involve primary autonomic failure. These diseases are pure autonomic failure, in which autonomic impairment (that is, orthostatic hypotension and bladder and sexual dysfunction) occurs alone; Parkinson disease, in which autonomic failure is combined with an extrapyramidal movement disorder; and multiple-system atrophy (also called Shy–Drager syndrome), in which autonomic failure is combined with an extrapyramidal or cerebellar movement disorder or both (1).

During the early stages of multiple-system atrophy, autonomic deficits may be the sole clinical manifestation; therefore, the disease may resemble pure autonomic failure. However, after a variable period that can be as long as several years, extrapyramidal or cerebellar deficits or both invariably develop. In Parkinson disease, extrapyramidal motor problems are the presenting feature; later in the disease process, patients may develop severe autonomic failure, making it difficult to distinguish between Parkinson disease and multiple-system atrophy. To further complicate the distinction, some patients with multiple-system atrophy display motor deficits similar to those seen in Parkinson disease before autonomic failure is apparent.

In clinical practice, all of these possibilities lead to two main diagnostic problems. First, it cannot be determined whether a patient who is thought to have pure autonomic failure and whose only finding is autonomic failure will develop more widespread nonautonomic neuronal damage and be found to have multiple-system atrophy. Second, it may be difficult to determine whether a patient with autonomic failure and a parkinsonian movement disorder has Parkinson disease or multiple-system atrophy.

In addition to clinical criteria, several tests have been used to distinguish among Parkinson disease, …