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Dysautonomia (or autonomic dysfunction, autonomic neuropathy) is a condition in which the autonomic nervous system (ANS) malfunctions. It is an umbrella term for various forms of ANS malfunction. 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, such as difficulty adapting to changes in posture, as well as 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
- Excessive sweating or lack of sweating (ahydrosis)
- Heat intolerance brought on with activity and exercise
- Sexual problems including erectile dysfunction in men and vaginal dryness and orgasmic difficulties in women
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:
- Autoimmune disorders including Sjogren'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
- Chronic alcohol misuse
- Some bacterial infections (Lyme disease and tuberculosis)
- 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.
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 may be done to check for disorders that can cause the autonomic disorder include:
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.
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.
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.
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.
- Familial dysautonomia
- Postural orthostatic tachycardia syndrome
- Dopamine beta hydroxylase deficiency
- Peripheral nervous system
- Autonomic nervous system