Autonomic function testing

Overview

Autonomic function testing is a set of painless tests that check how well your autonomic nervous system is working. This system controls things your body does automatically, like your heart rate, blood pressure, digestion, and sweating. The tests help doctors find out if there's a problem with this system.

Autonomic function testing is not a routine screening test. It is used when a person has symptoms that suggest a problem with the autonomic nervous system.

The test is often recommended for people who experience dizziness, fainting, rapid heartbeat, abnormal sweating, or digestive issues that cannot be explained by other causes. It can affect people of any age, but it is more common in adults with certain conditions like diabetes or Parkinson's disease.

Symptoms

Common symptoms

• Dizziness or lightheadedness when standing up
• Fainting or nearly fainting
• Rapid or irregular heartbeat
• Excessive sweating or lack of sweating
• Digestive problems like bloating or constipation

Symptoms in children

• Fainting during school or physical activity
• Complaints of feeling 'weird' or 'wobbly'
• Unexplained tiredness and trouble concentrating

Symptoms in older adults

• Falls or near-falls when standing up
• Feeling dizzy after meals
• Changes in bowel or bladder function

Causes

Main causes

• Autonomic function testing is used to evaluate symptoms that may be caused by conditions such as diabetes, Parkinson's disease, multiple system atrophy, or autoimmune disorders.
• It can also help diagnose postural orthostatic tachycardia syndrome (POTS) or neurogenic orthostatic hypotension.

Risk factors

• Having a chronic illness like diabetes or Parkinson's disease
• Being older, as the autonomic system can naturally become less efficient with age
• Having a family history of autonomic disorders

When to see a doctor

See a doctor urgently if:

• If you faint and hit your head or have chest pain
• If you have a seizure or lose consciousness for more than a minute

Book a routine appointment if:

• If you often feel dizzy when standing up
• If you have episodes of rapid heartbeat without an obvious cause
• If you notice changes in sweating or digestion that concern you

Diagnosis

Autonomic function testing is done by a specialist, often a neurologist or a cardiologist. The doctor will first discuss your symptoms and medical history, then perform one or more specific tests to check how your autonomic system reacts to different challenges.

Tests that may be done

• Tilt table test: You lie on a table that tilts upward while your heart rate and blood pressure are monitored.
• Heart rate variability test: You breathe deeply at a set pace while your heart rate is recorded.
• QSART (quantitative sudomotor axon reflex test): A small device measures how much you sweat in different spots on your skin.
• Valsalva maneuver: You blow into a tube to create pressure, and your blood pressure response is measured.

What to expect at your appointment

The tests are usually done in a clinic or hospital outpatient department. They are painless and take about an hour or two. You may be asked to wear loose clothing and avoid caffeine or certain medications beforehand. You will be monitored closely, and you can ask questions anytime.

Treatment

Treatment depends on what the tests reveal. If an underlying cause is found, such as diabetes or an autoimmune condition, that condition is treated first. For many autonomic problems, the goal is to manage symptoms and prevent complications.

Self-care at home

• Stay well hydrated, especially in hot weather or during exercise.
• Avoid sudden changes in position – sit up slowly, then stand.
• Wear compression stockings to help blood flow in your legs.
• Elevate the head of your bed to reduce morning dizziness.

Medical treatments

Depending on your specific symptoms, your doctor may suggest medicines to help raise blood pressure, control heart rate, or improve sweating. These treatments are tailored to your needs and are started at low doses to minimize side effects. Always follow your doctor's advice carefully.

When is surgery considered?

Surgery is rarely needed for autonomic problems. In very specific cases, such as a tumor affecting the autonomic nerves, surgery may be considered.

Living with this condition

Living with autonomic symptoms can be challenging, but many people find ways to adapt. Planning your day around symptoms, taking breaks when needed, and learning your triggers can help you stay active and safe.

Lifestyle tips

• Avoid very hot environments, like hot baths or saunas, which can worsen dizziness.
• Exercise regularly with gentle, seated or recumbent activities like cycling or swimming.
• Keep a diary of symptoms to identify patterns and share with your doctor.

Diet and exercise

A balanced diet with enough salt and fluids (as advised by your doctor) can help maintain blood pressure. Gentle exercise that doesn't involve sudden standing, such as yoga or stationary biking, can improve circulation and overall health.

Mental health and emotional wellbeing

Dealing with unpredictable symptoms like fainting or rapid heartbeat can cause anxiety or low mood. It's normal to feel worried, and talking to a counselor or joining a support group can be very helpful.

Prevention

Autonomic problems themselves cannot always be prevented, especially if they are linked to a chronic condition. However, managing underlying diseases like diabetes carefully can help reduce the risk of developing autonomic neuropathy.

Screening programmes

There is no routine screening for autonomic problems. Testing is done only when symptoms suggest a problem.

Complications

If left untreated

• Increased risk of falls and injuries from fainting
• Difficulty performing daily activities due to dizziness or fatigue
• Worsening of underlying conditions if left unmanaged

Long-term outlook

With proper diagnosis and management, most people with autonomic dysfunction can lead active, fulfilling lives. Treatments and lifestyle adjustments can often control symptoms effectively. Work closely with your healthcare team to find what helps you best.

Find support

International organisations

• International Autonomic Neuroscience Society

Local organisations

• NHS UK - Autonomic Disorders Information · UK

Helplines

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