|Classification and external resources|
Dysautonomia (or autonomic dysfunction) is any disease or malfunction of the autonomic nervous system (ANS). The autonomic nervous system controls a number of functions in the body, such as heart rate, blood pressure, digestive tract peristalsis, and sweating, amongst others. Dysfunction of the ANS can involve any of these functions.
A number of conditions are forms of dysautonomia: postural orthostatic tachycardia syndrome (POTS), inappropriate sinus tachycardia (IST), vasovagal syncope, pure autonomic failure, neurocardiogenic syncope (NCS), neurally mediated hypotension (NMH), orthostatic hypotension, orthostatic hypertension, autonomic instability, and a number of lesser-known disorders such as cerebral salt-wasting syndrome. Dysautonomia may occur as the result of other diseases, such as diabetes mellitus, multiple system atrophy (Shy-Drager syndrome), Guillain-Barré syndrome and a number of other conditions that may affect the nervous system.
Signs and symptoms 
The symptoms of dysautonomia are numerous and vary widely from person to person. Since dysautonomia is a full-body condition, a large number of symptoms may be present that can greatly alter a person's quality of life. Each patient with dysautonomia is different—some are affected only mildly, while others are left completely bed-ridden and disabled.
The primary symptoms present in patients with dysautonomia are:
- Excessive fatigue
- Excessive thirst (polydipsia)
- Lightheadedness, dizziness or vertigo
- Feelings of anxiety or panic (not mentally induced)
- Rapid heart rate or slow heart rate
- Orthostatic hypotension, sometimes resulting in syncope (fainting)
Other symptoms frequently associated with dysautonomia include: Gastroparesis (delayed gastric emptying), headaches, pallor, malaise, facial flushing, salt cravings, mydriasis (abnormal dilation of the pupils), constipation, diarrhea, nausea, acid reflux, visual disturbances, orthostatic hypotension, numbness, nerve pain, trouble breathing, chest pains, in some cases loss of consciousness and seizures. Dysautonomia can also present with orthostatic hypertension. A full list of symptoms may be found at the Dysautonomia Information Network.
Causes of dysautonomias are not fully understood, but they are thought to include:
- Autoimmune disorders
- Lyme disease
- Diabetes mellitus
- Brain injury
- Degenerative neurological diseases such as Multiple System Atrophy and Parkinson's disease
- Genetic factors
- Hereditary connective tissue diseases, especially Ehlers-Danlos Syndrome. In a study on orthostatic intolerance and EDS, it is suggested that the co-occurrence of these syndromes can be attributed to the abnormal connective tissue in dependent blood vessels of those with EDS, which permits veins to distend excessively in response to ordinary hydrostatic pressures. This in turn leads to increased venous pooling and its hemodynamic and symptomatic consequences.
- Physical trauma or injury which damages the autonomic nervous system, as with Cerebral salt-wasting syndrome.
- Mitochondrial diseases
- Spinal cord injury (autonomic dysreflexia)
- Hereditary forms, often together with a sensory neuropathy (hereditary sensory and autonomic neuropathy, five types)
In some cases, a cardiac ablation procedure can be performed to stop the heart symptoms completely. It is not recommended in POTS patients, and can in fact worsen tachycardia. Medications are also used to stabilize the condition on a long-term basis. Benzodiazepines can be used for some of the physical problems such as anxiety. In many cases treatment of primary dysautonomia is symptomatic and supportive. Measures to combat orthostatic intolerance include elevation of the head of the bed, frequent small meals, a high-salt diet, fluid intake, and compression stockings. Drugs such as fludrocortisone, midodrine, ephedrine and SSRIs can also be used to treat symptoms. Treating dysautonomia can be difficult and usually requires a combination of drug therapies.
The outlook for patients with dysautonomia depends on the particular diagnostic category. Some forms of dysautonomia resolve over time and are not life threatening, even if life-changing in the form of minor to major limitations in activities of daily living. Patients with chronic, progressive, generalized dysautonomia in the setting of central nervous system degeneration have a generally poor long-term prognosis. Death can occur from pneumonia, acute respiratory failure, or sudden cardiopulmonary arrest in such patients. 
See also 
- Dopamine beta hydroxylase deficiency
- Familial dysautonomia
- Postural orthostatic tachycardia syndrome
- Tierney, Lawrence M.; McPhee, Stephen J.; Papadakis, Maxine A. (2006). Current Medical Diagnosis and Treatment 2007 (Current Medical Diagnosis and Treatment). McGraw-Hill Professional. p. 1010. ISBN 0-07-147247-9.
- Baguley IJ, Heriseanu RE, Cameron ID, Nott MT, Slewa-Younan S (2008). "A critical review of the pathophysiology of dysautonomia following traumatic brain injury". Neurocrit Care 8 (2): 293–300. doi:10.1007/s12028-007-9021-3. PMID 17968518.
- Wishart, Steven, and Graeme J. A. Macphee. “Evaluation and Management of the Non-Motor Features of Parkinson’s Disease.” Therapeutic Advances in Chronic Disease 2, no. 2 (March 2011): 69–85. doi:10.1177/2040622310387847. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3513877/?report=reader#section15-2040622310387847title
- J Pediatr. 1999 Oct;135(4):494-9. Orthostatic intolerance and chronic fatigue syndrome associated with Ehlers-Danlos syndrome. Rowe PC, Barron DF, Calkins H, Maumenee IH, Tong PY, Geraghty MT.
- Alexander MS, Biering-Sorensen F, Bodner D, et al. (January 2009). "International standards to document remaining autonomic function after spinal cord injury". Spinal Cord 47 (1): 36–43. doi:10.1038/sc.2008.121. PMID 18957962.
- Axelrod FB (2002). "Hereditary sensory and autonomic neuropathies. Familial dysautonomia and other HSANs". Clin Auton Res. 12. Suppl 1 (7): I2–14. doi:10.1007/s102860200014. PMID 12102459.
- "Dysautonomia". NINDS. Retrieved 2012-04-03.
- Dysautonomia at the Open Directory Project
- dysautonomia at NINDS
- Dysautonomia Youth Network of America, Inc.
- 12 More Pages-Live & Cope with Dysautonomia
- Dysautonomia Information Network
- Handbook for Patients with Dysautonomia, by Dr. David S. Goldstein, MD, PhD and Linda J. Smith - Free chapter by chapter PDF download