Autonomic Neuropathy

How the autonomic nervous system works

The autonomic nervous system works without conscious control. Its two branches, the sympathetic ("fight or flight") and parasympathetic ("rest and digest") systems, balance heart rate, blood pressure, digestion, bladder emptying, sexual function, pupil size and body temperature. In autonomic neuropathy, the small nerve fibers carrying these signals are damaged, so organs respond slowly, too much or not at all.

Symptoms

Symptoms depend on which organs are affected and often build slowly over years.

Causes

Diabetes

Long-standing, poorly controlled diabetes, type 1 or type 2, is the leading cause. Cardiovascular autonomic neuropathy is found in a significant share of people who have had diabetes for many years. It usually occurs alongside peripheral neuropathy in the feet. Risk rises with high blood sugar, high blood pressure, smoking, obesity and high cholesterol.

Other causes

• Amyloidosis: abnormal protein deposits, including hereditary transthyretin (ATTR) amyloidosis
• Autoimmune conditions: Sjögren's syndrome, lupus, rheumatoid arthritis, celiac disease, and autoimmune autonomic ganglionopathy
• Guillain-Barré syndrome: can cause dangerous swings in blood pressure and heart rate
• Infections: HIV, Lyme disease, botulism, leprosy
• Alcohol misuse
• Medicines: chemotherapy (vincristine, cisplatin), some heart medicines
• Paraneoplastic syndromes linked to cancer
• Inherited conditions: familial dysautonomia and hereditary sensory and autonomic neuropathies
• Brain disorders that affect autonomic control, such as Parkinson's disease and multiple system atrophy (these are not neuropathies but cause similar symptoms)

Diagnosis

A doctor will review symptoms system by system, examine for peripheral neuropathy and check medicines that can cause similar problems. Tests include:

• lying and standing blood pressure and heart rate, measured after 1 and 3 minutes of standing
• heart rate variability tests: response to deep breathing and the Valsalva maneuver, often in an autonomic lab
• tilt-table test
• quantitative sweat tests (QSART) or thermoregulatory sweat test
• gastric emptying study for suspected gastroparesis
• bladder ultrasound after voiding and urodynamic testing
• blood tests: HbA1c, B12, thyroid, protein electrophoresis, and tests for amyloidosis or autoimmune disease
• skin biopsy to count small nerve fibers

People with diabetes should be screened for autonomic neuropathy as recommended, often starting 5 years after type 1 diagnosis and at diagnosis of type 2.

Treatment

Treat the cause

• Good blood sugar control, along with control of blood pressure, cholesterol and weight, slows progression in diabetes.
• Specific treatment for amyloidosis, autoimmune conditions or vitamin deficiencies.
• Stopping alcohol and reviewing medicines.

Dizziness on standing

• Stand up slowly, use leg-crossing and muscle-tensing maneuvers.
• Drink more fluid and, if your doctor agrees, increase salt.
• Compression stockings or an abdominal binder.
• Raise the head of the bed.
• Medicines such as midodrine, fludrocortisone or droxidopa.
• Review blood pressure medicines that may be worsening it.

Digestive symptoms

• Smaller, more frequent, low-fat, low-fiber meals for gastroparesis, with medicines that help the stomach empty or reduce nausea.
• Fiber, fluids and laxatives for constipation, and antidiarrheal medicines or treatment for bacterial overgrowth for diarrhea.

Bladder

• Timed voiding and double voiding.
• Intermittent self-catheterization if the bladder does not empty.
• Prompt treatment of urinary infections.

Sexual function

• PDE5 inhibitors for erectile dysfunction (not with nitrates), vacuum devices or injections.
• Vaginal lubricants and moisturizers.

Sweating and temperature

• Avoid overheating and dress in layers, because reduced sweating raises the risk of heat illness.
• Treatments for excessive upper-body sweating.

Low blood sugar awareness

Continuous glucose monitors with alarms help people who no longer feel warning signs.

Complications and outlook

Cardiovascular autonomic neuropathy is linked to a higher risk of heart rhythm problems, silent heart attacks and earlier death in people with diabetes, so regular heart checks matter. Falls, malnutrition from gastroparesis, urinary infections and dangerous hypoglycemia are other risks. The nerve damage is usually permanent, but early detection and good control of the cause can slow it, and symptom treatments help most people stay active.

Frequently asked questions

What are the symptoms of autonomic neuropathy?

Common symptoms are dizziness or fainting when standing, feeling full quickly, nausea and vomiting, constipation or diarrhea, bladder problems, erectile dysfunction, abnormal sweating, heat intolerance and a fast resting heart rate. People with diabetes may lose the warning signs of low blood sugar.

What is the most common cause of autonomic neuropathy?

Diabetes is the most common cause. Years of high blood sugar damage the small nerves controlling automatic functions. Other causes include amyloidosis, autoimmune diseases, alcohol misuse, HIV, chemotherapy and inherited conditions.

Can autonomic neuropathy be reversed?

Usually not completely. Good blood sugar control and treatment of other causes can slow or sometimes partly improve it, especially early on. Autonomic neuropathy caused by treatable conditions, such as some autoimmune forms, may improve with treatment.

How is autonomic neuropathy diagnosed?

Doctors measure blood pressure and heart rate lying and standing, test heart rate responses to deep breathing, and may use tilt-table, sweat, stomach emptying and bladder tests. Blood tests look for causes such as diabetes and amyloidosis.

Is autonomic neuropathy the same as dysautonomia?

Dysautonomia is a broad term for any disorder of the autonomic nervous system, including POTS and multiple system atrophy. Autonomic neuropathy is one type of dysautonomia, caused specifically by damage to the autonomic nerves.