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Diseases of the autonomic nervous system 

Diseases of the autonomic nervous system

Chapter:
Diseases of the autonomic nervous system
Author(s):

Christopher J. Mathias

and David A. Low

DOI:
10.1093/med/9780199204854.003.02414_update_001

November 27, 2014: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Intermittent autonomic dysfunction—classifications revised, including addition of diagnosis of initial orthostatic hypotension.

Prognosis—expanded discussion of prognosis of different types of autonomic disorder.

Investigations—more detailed discussion, in particular of physiological and pharmacological tests.

Particular conditions—updates on postural tachycardia syndrome (PoTS) and initial orthostatic hypotension.

Treatment—use of l-dihydroxyphenylserine (L-DOPS).

Updated on 28 Nov 2012. The previous version of this content can be found here.
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date: 25 March 2017

The autonomic nervous system innervates all organs, producing predominantly involuntary and automatic actions that are mediated by two principal efferent pathways, the sympathetic and parasympathetic, which are neurochemically and anatomically distinct. Numerous synaptic relays and neurotransmitters allow the autonomic control of organ function at local and central levels to be integrated with the requirements of the whole body.

The peripheral and central components of the autonomic nervous system are frequently affected by diseases, conditions, or toxins. Autonomic disorders are described as (1) primary—without defined cause, including multiple system atrophy and acute/subacute dysautonomias; or (2) secondary—with specific defects or as a consequence of other conditions, including diabetes mellitus, Riley–Day syndrome, amyloid neuropathy, dopamine β‎-hydroxylase deficiency, spinal cord injury, and many drugs.

Clinical features

Failure of the autonomic nervous system—manifestations may be (1) sympathetic—adrenergic failure causes postural hypotension and (in men) disturbed ejaculation; cholinergic disturbances interfere with sweating; (2) parasympathetic—causing a fixed heart rate, erectile failure, and disturbed emptying of the urinary bladder and large intestine.

Overactivity of the autonomic nervous system—manifestations may be (1) sympathetic—characterized by hypertension, tachycardia and excessive sweating; (2) parasympathetic—leading to bradycardia. Mixed effects, peripherally and centrally, lead to complex clinical manifestations.

Investigation

Autonomic screening tests include (1) cardiovascular—(a) physiological—e.g. head-up tilt, heart rate responses, (b) biochemical—e.g. plasma noradrenaline, adrenaline, and dopamine levels, (c) pharmacological—e.g. clonidine growth-hormone stimulation; (2) sweating—e.g. thermoregulatory response to increasing core temperature by 1 °C. Autonomic dysfunction may also be suggested by a wide variety of other tests, including those of gastrointestinal, urinary/renal, sexual, respiratory and eye function.

Treatment

Symptomatic—(1) Orthostatic hypotension—management requires an approach combining (a) nonpharmacological measures—e.g. avoidance of sudden standing, high salt intake; and (b) pharmacological measures—e.g. fludrocortisone, sympathomimetics (e.g. ephedrine, midodrine). (2) Other symptoms—combined pharmacological and physical interventions can improve urinary incontinence, gastrointestinal motility disorders, and sexual dysfunction. Care is required to manipulate autonomic activity in patients with parkinsonian manifestations because the autonomic aspects are frequently exacerbated by antiparkinsonian agents.

Specific—some causes of autonomic dysfunction are treatable, e.g. infusions of immunoglobulin and plasmapheresis for immune-mediated neuropathy; hepatic transplantation in familial amyloid polyneuropathy.

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