A consensus statement generated by the American Autonomic Society and the American Academy of Neurology defines the various primary neurogenic causes of autonomic dysfunction. Implicit in this document is the need to bid good-bye to the use of the term "Shy-Drager syndrome" to identify a condition that was first described in 1962.
Milton Shy and Glen Drager detailed the clinical features of two patients who had both orthostatic hypotension and central nervous system signs, and they carefully studied the neuropathologic changes in one of these patients. Their conclusion that orthostatic hypotension and central nervous system dysfunction were probably related is obvious today but at the time seemed prescient. Although some previous reports had described these disparate phenomena in the same patients, no one had claimed that the two were related. Shy and Drager described several aspects of autonomic dysfunction -- in addition to orthostatic hypotension -- and meticulously delineated various signs of degeneration of the cerebellar, extrapyramidal, and pyramidal systems. Since their seminal report, burgeoning interest in autonomic disorders has spawned studies outlining the clinical and neuropathologic findings in such patients. This research resulted in a far greater understanding of the interplay between structural defects and functional outcomes but inevitably added to a confusing array of terms.
"Multiple system atrophy" is now the favored term; the condition is defined as a sporadic, progressive, adult-onset disorder characterized by autonomic dysfunction, parkinsonism, and ataxia in any combination. Its features include "parkinsonism (usually with a poor response to Levodopa), cerebellar or corticospinal signs, and orthostatic hypotension, impotence, and urinary incontinence, or retention ... when autonomic failure predominates, the term Shy Drager syndrome is often used".
The current nosology for autonomic disorders is best summarized as follows:
Complicating this construct is the fact that some patients with pure autonomic failure may progress after a period of stability into multiple system atrophy, which affects some but not all areas of the central nervous system in various ways. Graham and Oppenheimer accordingly wondered if there were more than one disease process. A key feature, autonomic dysfunction (with its resultant orthostatic hypotension), may or may not be associated with cerebellar or parkinsonian features, attributed to either olivopontocerebellar atrophy or striatonigral degeneration. This complex classification was not well served by the term "Shy-Drager syndrome"; thus, some consensus on new terminology was needed. An agreement was hammered out in which "multiple system atrophy" was substituted for "Shy-Drager syndrome." At the very least, this nomenclature implies that more than one area in the central nervous system is involved in the process.
Multiple system atrophy had to be divided into three categories:
Eponyms in medicine have a curious history. Some are retained even though they may mean substantially different things to different people (for example, Parkinson disease, Parkinson syndrome, and parkinsonism). A few disappear relatively quickly -- only older cardiologists know that the Barlow syndrome is the same as mitral valve prolapse. The current fashion, however, is to be as descriptive as possible. Dopamine beta-hydroxylase deficiency accurately and precisely recounts the mechanism of this rare disease; because of inadequate amounts of this substance, patients with the disorder have autonomic dysfunction, including orthostatic hypotension. If it had been named "Robertson disease" (after the author of the original description), as indeed it might have been not too many years ago, what would have been gained in honoring an astute observation would have been more than lost in not providing an instantaneous description of its basic mechanism. McKusick and colleagues rightly emphasize that "... a desideratum in nomenclature is terminology based on the nature of the fundamental defect." Nonetheless, some eponyms are so ingrained in common medical usage that they are impossible to eradicate. Addison disease and Chagas disease immediately come to mind, and, although these conditions have alternative and more precise titles, the eponyms will always be with us. It seems likely that as causes and pathogenetic mechanisms become better understood, the resulting nomenclature will be more precise and the naming of conditions for persons will become rare.
Is all of this of more than marginal interest to the practicing internist? In fact, the consensus committee that drafted the document included neurologists, cardiologists, endocrinologists, and clinical pharmacologists. Orthostatic hypotension is more and more frequently recognized as a serious problem; recent data show that the prevalence of this condition in independently living, elderly Japanese-American men ranges from 5.1% to 10.9%. The evaluation of syncope in the cardiac electrophysiology laboratory, with the ubiquitous use of the tilt Table to induce postural blood pressure and heart rate changes, is commonplace. Distinguishing among neurocardiogenic syncope, vasovagal syncope, and orthostatic hypotension is complex and confusing for many internists. In patients who turn out to have a clinically significant and symptomatic decrease in blood pressure when they stand up, the physician must then tease out the various causes of this clinical defect, including pure autonomic failure, with its relatively good prognosis; Parkinson disease, in which the patient's condition may be stable for long periods; and multiple system atrophy, which imparts a 4- to 6-year downhill course.
Although a perfect nomenclature in this area does not yet exist, the suggested changes are a step forward. The goal will be to establish a terminology that clearly reflects both cause and dysfunction. Further sorting of these varied neurologic disorders may take some time, but it is hoped that the newer techniques of proton magnetic imaging spectroscopy and positron emission tomography may bring important clues to cause and pathogenesis. In the meantime, we must make do with "multiple system atrophy," and, a little reluctantly, bid a fond farewell to the "Shy-Drager syndrome."