Autonomic Dysfunction (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, tightens blood vessels to maintain blood pressure, increases sweating and slows digestion.
• Parasympathetic ("rest and digest"): slows the heart, stimulates digestion and controls bladder emptying and sexual function.

When these nerves or their control centers in the brain are damaged or malfunction, the body cannot adjust properly, for example when standing up, eating, or getting hot.

Symptoms

Heart and blood pressure

• lightheadedness, dizziness or blurred vision when standing, especially in the morning, after meals or in heat
• fainting or near-fainting
• a fast heart rate on standing (in POTS)
• exercise intolerance and fatigue
• high blood pressure when lying down in some types

Digestive

• feeling full quickly, nausea, bloating and vomiting (from gastroparesis)
• constipation, diarrhea or both
• difficulty swallowing

Bladder and sexual function

• urgency, frequency, incomplete emptying or retention
• erectile dysfunction and ejaculation problems
• vaginal dryness and reduced arousal

Sweating and temperature

• reduced or absent sweating, heat intolerance and overheating
• excessive sweating in some areas, sometimes to compensate for others
• cold, discolored hands and feet

Other

• pupils slow to adjust to light or dark
• dry eyes and mouth
• sleep problems, brain fog and fatigue

Types and causes

Postural orthostatic tachycardia syndrome (POTS)

In POTS, the heart rate rises by 30 beats per minute or more (40 or more in teenagers) within 10 minutes of standing, without a big fall in blood pressure. It mostly affects women aged 15 to 50 and often starts after a viral illness, including COVID-19, pregnancy or surgery. It is linked with joint hypermobility. Symptoms include lightheadedness, palpitations, fatigue and brain fog.

Vasovagal (reflex) syncope

The most common cause of fainting. Triggers such as standing for long periods, heat, pain or the sight of blood cause a sudden drop in heart rate and blood pressure. See vasovagal syncope.

Orthostatic hypotension

Orthostatic hypotension is a fall in blood pressure of at least 20 mmHg systolic or 10 mmHg diastolic within 3 minutes of standing. When caused by nerve damage (neurogenic), the heart rate does not rise to compensate. Medicines and dehydration are common non-nerve causes.

Autonomic neuropathy

Damage to the autonomic nerves themselves. Causes include:

• diabetes, the most common cause, usually after many years and alongside nerve damage in the feet
• amyloidosis
• autoimmune conditions such as Sjogren's syndrome and autoimmune autonomic ganglionopathy
• Guillain-Barre syndrome
• chemotherapy and other toxic medicines, and heavy alcohol use
• HIV and other infections
• inherited neuropathies

See autonomic neuropathy.

Brain conditions

• Parkinson's disease and Lewy body dementia: constipation, orthostatic hypotension and bladder problems are common and can come before movement symptoms.
• Multiple system atrophy: a rare, progressive condition with severe autonomic failure plus Parkinson-like or balance problems.
• spinal cord injury, which can cause dangerous spikes in blood pressure (autonomic dysreflexia) with injuries above the mid-chest level.

Diagnosis

• History and medicines review: many medicines lower blood pressure or affect heart rate.
• Lying and standing blood pressure and heart rate: measured after lying for 5 minutes, then at 1 and 3 minutes (and up to 10 minutes for POTS) of standing.
• Tilt-table test: you lie on a table that tilts upright while heart rate and blood pressure are monitored.
• Autonomic reflex tests: heart rate response to deep breathing and the Valsalva maneuver.
• Sweat tests: quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test, or skin biopsy for small nerve fibers.
• Blood tests: glucose and HbA1c, B12, thyroid function, and tests for autoimmune or amyloid disease.
• Other tests: gastric emptying studies, bladder scans, and an ECG and heart ultrasound to exclude heart causes of fainting.

Treatment

Lifestyle measures

• Fluids: about 2 to 3 liters a day, unless your doctor advises otherwise.
• Salt: increased salt intake for POTS and orthostatic hypotension, if blood pressure and heart health allow.
• Stand up slowly, sit on the edge of the bed first, and cross your legs or clench your buttocks when standing.
• Compression garments: waist-high stockings or abdominal binders.
• Exercise reconditioning: start with recumbent exercise such as rowing, recumbent cycling or swimming, and build up gradually.
• Small, frequent meals, lower in refined carbohydrates, to reduce blood pressure drops after eating.
• Raise the head of the bed for people with high blood pressure when lying down.
• Avoid triggers such as heat, hot showers, alcohol and long periods of standing.

Medicines

• Fludrocortisone to expand blood volume.
• Midodrine or droxidopa to tighten blood vessels.
• Beta-blockers or ivabradine to slow the heart rate in POTS.
• Pyridostigmine in some cases.
• Specific treatments for gastroparesis, constipation, bladder problems and erectile dysfunction.
• Treating the cause, such as improving diabetes control or immune therapy for autoimmune causes.

Outlook

The outlook depends on the cause. Vasovagal syncope and many cases of POTS improve over time, especially in young people, with lifestyle measures. Diabetic autonomic neuropathy can be slowed with good blood sugar control. Neurodegenerative causes such as multiple system atrophy progress over years, and treatment focuses on comfort and safety.

Frequently asked questions

What are the symptoms of dysautonomia?

Common symptoms are dizziness or fainting when standing, a racing heart, fatigue, brain fog, exercise intolerance, bloating, nausea, constipation, bladder problems, sexual dysfunction and abnormal sweating. Symptoms vary widely depending on which nerves are affected.

What causes autonomic dysfunction?

Common causes include diabetes, viral infections (often preceding POTS), Parkinson's disease, multiple system atrophy, amyloidosis, autoimmune conditions, some medicines, heavy alcohol use and spinal cord injury. In many people with POTS, no single cause is found.

Is dysautonomia serious?

It ranges from mild to severe. Vasovagal syncope and many cases of POTS are disruptive but not life-threatening and often improve. Autonomic failure from Parkinson's disease or multiple system atrophy can be more serious. Fainting carries injury risk, so all cases deserve assessment.

How is dysautonomia treated?

Most people start with more fluids and salt, compression garments, gradual exercise and avoiding triggers. Medicines such as fludrocortisone, midodrine or beta-blockers help when these are not enough. Treating the underlying cause, such as diabetes, is also important.