Dysautonomia

Dysautonomia (or autonomic dysfunction, autonomic neuropathy) is an umbrella term for various conditions in which the autonomic nervous system (ANS) does not work correctly. Dysautonomia is a type of neuropathy affecting the nerves that carry information from the brain and spinal cord to the heart, bladder, intestines, sweat glands, pupils, and blood vessels. Dysautonomia may be experienced in a number of ways, depending on the organ system involved, for example difficulty adapting to changes in posture, or digestive symptoms.

The diagnosis is achieved through functional testing of the autonomic nervous system, focusing on the organ system affected. Investigations may be performed to identify underlying disease processes that may have led to the autonomic neuropathy that is causing the dysautonomia. Symptomatic treatment is available for many symptoms associated with autonomic neuropathy, and some disease processes can be treated directly.

Signs and symptoms

The symptoms of dysautonomia are numerous and vary widely from person to person depending on the nerves affected and underlying cause. Symptoms often develop gradually over years. Each patient with dysautonomia is different—some are affected only mildly, while others are often left disabled.

The primary symptoms present in patients with dysautonomia include:

• Excessive fatigue
• Excessive thirst (polydipsia)
• Lightheadedness or dizziness, often associated with orthostatic hypotension (abnormally low blood pressure on standing), sometimes resulting in syncope (fainting)
• Rapid heart rate or slow heart rate
• Blood pressure fluctuations
• Difficulty with breathing or swallowing
• Shortness of breath with activity or exercise
• Distension of the abdomen
• Mydriasis (abnormal dilation of the pupils) leading to blurry vision
• Urinary incontinence or neurogenic bladder dysfunction
• Gastroparesis (delayed gastric emptying) with associated nausea, acid reflux and vomiting
• Constipation
• Excessive sweating or lack of sweating (anhydrosis)
• Heat intolerance brought on with activity and exercise
• Sexual problems including erectile dysfunction in men and vaginal dryness and orgasmic difficulties in women

Causes

Dysautonomia may be due to inherited or degenerative neurologic diseases (primary dysautonomia) or it may occur due to injury of the autonomic nervous system from an acquired disorder (secondary dysautonomia). Side effects of drugs can cause abnormalities in the function of the autonomic nervous system, producing an iatrogenic form of dysautonomia.

The most common causes of dysautonomia include:

• Heavy metal poisoning
• Autoimmune disorders including Sjögren's syndrome, lupus, sarcoidosis, Anti-NMDA receptor encephalitis
• Diabetes mellitus
• Multiple sclerosis
• Parkinson's disease (in advanced parkinsonism or early in multiple system atrophy)
• HIV and AIDS
• Hereditary disorders including familial dysautonomia and Ehlers-Danlos syndrome
• Pure autonomic failure
• Amyloidosis
• Botulism
• Chronic alcohol misuse
• Some bacterial infections: (Lyme disease, tuberculosis, and Helicobacter pylori)
• Spinal cord injury
• Surgery or injury involving the nerves
• Physical trauma or injury
• Closed brain injury caused by asphyxiation, poisoning or encephalitis

Sympathetic nervous system-predominant dysautonomia is common in fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, and interstitial cystitis, raising the possibility that such dysautonomia could be their common clustering underlying pathogenesis.^[1]

Mechanism

The autonomic nervous system (ANS) is a component of the peripheral nervous system and is made up of two branches: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The SNS controls the more active "fight or flight" responses such as increasing heart rate and blood pressure. The PNS can be thought of as the "rest and digest" part of the autonomic nervous system, as it slows down the heart rate and aids in digestion. Symptoms typically arise from abnormal responses of either the sympathetic or parasympathetic systems based on situation or environment.

Diagnosis

Dysautonomia does not produce unique symptoms. It is the set of symptoms, taken together, that suggests that a dysautonomic state is present. The patient's individual complaints can each be part of another disease process which often leads to misdiagnosis. Collaboration between many specialists is often necessary. Care is primarily directed by a neurologist.

Indications for laboratory evaluation include:

• Diagnosis of generalized autonomic failure
• Diagnosis of benign autonomic disorders
• Diagnosis of distal small fiber neuropathy
• Evaluation of orthostatic intolerance
• Evaluation for autonomic dysfunction in known peripheral neuropathies
• Detection of sympathetic dysfunction in sympathetically-mediated pain syndromes

Routine autonomic nervous system dysfunction tests include:

• Valsalva maneuver
• Tilt table test
• Gastric emptying tests
• Quantitative sudomotor axon reflex test (QSART)
• Thermoregulatory sweat test
• Urodynamic testing

Other tests which may be done to check for disorders that can cause the autonomic disorder include:

• Small fiber neuropathy biopsy
• Endocrine testing

Management

Treating dysautonomia can be difficult. There is no one scientifically proven treatment for dysautonomia. Since dysautonomia is made up of many different symptoms a combination of drug therapies is often required to manage individual symptomatic complaints.

Drugs such as fludrocortisone, midodrine, ephedrine and SSRIs and anticonvulsants can also be used to treat an assortment of symptoms with varying degrees of success. 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. Proton-pump inhibitors and H2 receptor antagonists are used for digestive symptoms such as acid reflux.

For cardiovascular symptoms, a cardiac ablation, or balloon angioplasty procedure, can be performed for heart related symptoms of ANS.

Dysautonomia secondary to autoimmune diseases or multiple sclerosis (MS) can often improve if the underlying disorder is diagnosed and therapy targeted for the underlying disorder is successful. Immunosuppressive treatment regimens have varying success in alleviating autonomic symptoms.

Prognosis

The outlook for patients with dysautonomia depends on the particular diagnostic category. Some autonomic nervous system disorders get better when an underlying disease is treated or offending agent is removed.

Cases secondary to autoimmune diseases, diabetes and MS are typically not life-threatening, though minor to major limitations in activities of daily living can occur.

Patients with chronic, progressive, generalized dysautonomia in the setting of central nervous system degeneration such as Parkinson's disease or multiple system atrophy have a generally poorer long-term prognosis. Death can occur from pneumonia, acute respiratory failure, or sudden cardiopulmonary arrest in such patients.^[2]

Often there is no cure. Damage to the nerves of the autonomic system is often not reversible, and comprehensive disease management is essential to improving patient quality of life.

See also

References

External links

• New York University Dysautonomia Center
• Dysautonomia at DMOZ
• Vanderbilt Autonomic Dysfunction Center
• Mayo Clinic
• dysautonomia at NINDS
• Autonomic Disorders Consortium
• Multiple System Atrophy Coalition