Dysautonomias: clinical disorders of the autonomic nervous system.
The term dysautonomia refers to a change in autonomic nervous system function that adversely affects health. The changes range from transient, occasional episodes of neurally mediated hypotension to progressive neurodegenerative diseases; from disorders in which altered autonomic function plays a primary pathophysiologic role to disorders in which it worsens an independent pathologic state; and from mechanistically straightforward to mysterious and controversial entities. In chronic autonomic failure (pure autonomic failure, multiple system atrophy, or autonomic failure in Parkinson disease), orthostatic hypotension reflects sympathetic neurocirculatory failure from sympathetic denervation or deranged reflexive regulation of sympathetic outflows. Chronic orthostatic intolerance associated with postural tachycardia can arise from cardiac sympathetic activation after "patchy" autonomic impairment or blood volume depletion or, as highlighted in this discussion, from a primary abnormality that augments delivery of the sympathetic neurotransmitter norepinephrine to its receptors in the heart. Increased sympathetic nerve traffic to the heart and kidneys seems to occur as essential hypertension develops. Acute panic can evoke coronary spasm that is associated with sympathoneural and adrenomedullary excitation. In congestive heart failure, compensatory cardiac sympathetic activation may chronically worsen myocardial function, which rationalizes treatment with beta-adrenoceptor blockers. A high frequency of positive results on tilt-table testing has confirmed an association between the chronic fatigue syndrome and orthostatic intolerance; however, treatment with the salt-retaining steroid fludrocortisone, which is usually beneficial in primary chronic autonomic failure, does not seem to be beneficial in the chronic fatigue syndrome. Dysautonomias are an important subject in clinical neurocardiology.
Goldstein
David S
DS
Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 10, Room 6N252, 10 Center Drive MSC-1620, Bethesda, MD 20892-1620, USA.
Robertson
David
D
Esler
Murray
M
Straus
Stephen E
SE
Eisenhofer
Graeme
G
D001341:Autonomic Nervous System / Q000503:physiopathology; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology*; D002319:Cardiovascular System / Q000503:physiopathology; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D016584:Panic Disorder / Q000503:physiopathology