Autonomic Nervous System Disorders (Dysautonomia)

What the autonomic nervous system does

The autonomic nervous system works without conscious control. It has two main branches:

• Sympathetic ("fight or flight"): raises heart rate and blood pressure, tightens blood vessels, increases sweating, slows digestion.
• Parasympathetic ("rest and digest"): slows the heart, stimulates digestion, controls the bladder and sexual arousal.

These nerves constantly adjust blood pressure when you stand, regulate body temperature and move food through the gut. When they fail, the problems can affect almost any organ.

Types of autonomic disorders

See also autonomic dysfunction for a symptom-focused overview.

Symptoms by body system

• Heart and circulation: dizziness, blurred vision or fainting on standing, especially in heat, after meals or in the morning; a racing or slow heart; exercise intolerance.
• Digestive: difficulty swallowing, early fullness, nausea, vomiting (gastroparesis), bloating, constipation or diarrhea, often alternating.
• Bladder: urgency, frequency, weak stream, incomplete emptying, recurrent infections.
• Sexual: erectile dysfunction, ejaculation problems, vaginal dryness.
• Sweating and temperature: too little sweating (heat intolerance, overheating) or excessive sweating in patches.
• Eyes: slow pupil adjustment to light changes, dry eyes and mouth.
• General: fatigue, brain fog, poor sleep, headaches.
• Hypoglycemia unawareness in people with diabetes, because warning symptoms rely on autonomic nerves.

Causes

• Diabetes: the most common cause of autonomic neuropathy, after years of high blood sugar.
• Neurodegenerative diseases: Parkinson's disease, multiple system atrophy, Lewy body dementia.
• Autoimmune conditions: Sjogren's syndrome, lupus, celiac disease, autoimmune autonomic ganglionopathy, Guillain-Barre syndrome.
• After infections: POTS commonly follows viral illnesses, including COVID-19.
• Amyloidosis (inherited or acquired).
• Medicines: blood pressure drugs, diuretics, antidepressants, chemotherapy.
• Alcohol misuse, vitamin B12 deficiency, HIV, spinal cord injury.
• Ehlers-Danlos syndrome (hypermobile type), which is associated with POTS.

Diagnosis

1. Active stand test: blood pressure and heart rate lying down and at 1, 3, 5 and 10 minutes after standing.
2. Tilt-table test: monitoring while tilted upright on a table, for unexplained fainting or POTS.
3. Autonomic reflex screen: heart rate response to deep breathing and the Valsalva maneuver.
4. Sweat tests: QSART or thermoregulatory sweat testing.
5. Gastric emptying study for gastroparesis, bladder scan or urodynamics for bladder symptoms.
6. Blood tests: glucose and HbA1c, B12, thyroid, autoimmune antibodies, and tests for amyloidosis.
7. Skin biopsy to count small nerve fibers.

Treatment

There is often no cure, but symptoms can be greatly improved.

Lifestyle measures

• drink 2 to 3 liters (about 64 to 100 oz) of fluid a day and, if your doctor agrees, increase salt
• stand up slowly; sit on the edge of the bed first
• wear waist-high compression stockings or an abdominal binder
• raise the head of the bed by 10 to 15 cm (4 to 6 inches) for orthostatic hypotension
• eat small, frequent, low-fat meals for gastroparesis and post-meal dizziness
• avoid hot showers, saunas and standing still for long periods
• recumbent exercise programs (rowing, swimming, recumbent bike), building up gradually, especially for POTS

Medicines

Depending on the problem: fludrocortisone, midodrine or droxidopa to raise blood pressure; beta-blockers or ivabradine to slow the heart in POTS; medicines that speed stomach emptying; bladder medicines or catheterization; erectile dysfunction treatments.

Treat the cause

Tight blood sugar control, immunotherapy for autoimmune autonomic disorders, stopping or changing medicines, and treating amyloidosis or B12 deficiency.

Outlook

The outlook varies. POTS often improves over years, especially in younger people. Reflex syncope is benign. Diabetic autonomic neuropathy can be slowed with good control. Multiple system atrophy and pure autonomic failure are progressive and need ongoing specialist care.

Frequently asked questions

What are the symptoms of dysautonomia?

Common symptoms include dizziness or fainting on standing, a racing heart, fatigue, brain fog, bloating, nausea, constipation, bladder problems, abnormal sweating and heat intolerance. Symptoms vary depending on which autonomic nerves are affected.

What is the most common autonomic disorder?

Reflex (vasovagal) syncope and orthostatic hypotension are the most common. POTS is common in young women. Diabetic autonomic neuropathy is the most common cause of autonomic nerve damage overall.

How is an autonomic disorder diagnosed?

Doctors measure blood pressure and heart rate lying and standing, and may use a tilt-table test, breathing and Valsalva tests, sweat tests and blood tests to look for causes such as diabetes or autoimmune disease.

Can dysautonomia be cured?

Some forms improve or resolve, such as POTS after a viral infection or dysautonomia caused by a medicine. Others, linked to diabetes or neurodegenerative disease, are long-term. Treatment with fluids, salt, compression, exercise and medicines usually improves daily life significantly.

Is dysautonomia the same as POTS?

No. POTS is one type of dysautonomia. Dysautonomia is the umbrella term for any disorder of the autonomic nervous system, including orthostatic hypotension, fainting disorders, autonomic neuropathy and multiple system atrophy.