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At a glance

A rare and devastating neurodegenerative disorder presenting clinically with severe autonomic failure, parkinsonism, cerebellar ataxia, and corticospinal tract signs in varying combinations. Now better known as multiple system atrophy.

Synonyms

Idiopathic Orthostatic Hypotension Syndrome; Olivopontocerebellar Atrophy (OPCA); Striatonigral Degeneration; Multiple System Atrophy.

History

Initially described in 1960 by G. M. Shy, an American Neurologist, and G. A. Drager, an American physician, in Houston, Texas.

Classification:

A new classification for the autonomic disorders has been best summarized as follows:

  • Primary or Cause Unknown: Described as a pure autonomic failure (previously called idiopathic orthostatic hypotension or the Bradbury-Eggleston Syndrome. It is clinically characterized by the absence of other neurological defects besides the autonomic dysfunction.

  • Multiple System Atrophy: A sporadic, progressive, adult-onset disorder characterized by the association of autonomic dysfunction, parkinsonism and ataxia in any combination.

Incidence

1.9 to 4.9/100,000, more common in males.

Genetic inheritance

Autosomal dominant.

Pathophysiology

Buildup of abnormally folded alpha-synuclein proteins in oligodendrocytes. Postmortem examination demonstrates degeneration of autonomic neurons in the intermediolateral columns, putamen, substantia nigra, locus ceruleus, inferior olivary nuclei, and degenerative change in peripheral ganglia. Loss of central sympathetic tone results in inability to vasoconstrict or to mount a tachycardia in response to posture changes causing hypotension. Involvement of the corticospinal, corticocerebellar, and pyramidal tracts later in the disease process gives rise to symptoms of parkinsonism.

Diagnosis

A consensus statement generated by the American Autonomic Society and the American Academy of Neurology, defining the various neurogenic causes of autonomic dysfunction, suggested abandonment of the term “Shy-Drager” Syndrome in 1996. History, demonstration of postural hypotension, and special investigations to demonstrate sympathetic insufficiency. Must exclude all other possible causes of orthostatic hypotension. It usually ends in death 7 to 10 years after the onset of symptoms.

Clinical aspects

Symptoms include dizziness on rising, syncope, and anhydrosis. Sexual dysfunction, urinary incontinence, fecal incontinence, dysphagia, unequal pupils, atrophy of the iris, external ophthalmoplegia, and wasting of distal limb muscles all reflect the degenerative changes within the central nervous system and autonomic ganglia. Nocturnal polyuria and natriuresis are present early in the natural history of the disease and cause relative hypovolemia and exacerbation of hypotension on rising from bed. Central sleep apnea has been demonstrated on rare occasions. Signs and symptoms of bradykinesia, rigidity, and tremor occur following a variable interval (ranging from weeks to years) after development of orthostatic hypotension. An abnormal response to the Valsalva maneuver is easily demonstrated. Special investigations include stress tests to show absent sympathetic response; demonstration of lack of response to atropine; assessment of ability to sweat; infusion of direct-acting sympathomimetic agents, which causes hypertension ...

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