Autonomic neuropathy

Definition

Autonomic neuropathy is a group of symptoms that occur when there is damage to nerves that regulate blood pressure, heart rate, bowel and bladder emptying, digestion, and other body functions.

Alternative Names

Neuropathy - autonomic

Causes, incidence, and risk factors

Autonomic neuropathy is a form of peripheral neuropathy. It is a group of symptoms, not a specific disease. There are many causes.

Autonomic neuropathy involves damage to the nerves that run through a part of the peripheral nervous system. The peripheral nervous system includes the nerves used for communication to and from the brain and spinal cord (central nervous system) and all other parts of the body, including the internal organs, muscles, skin, and blood vessels.

Damage to the autonomic nerves affects the function of areas connected to the problem nerve. For example, damage to the nerves of the gastrointestinal tract makes it harder to move food during digestion (decreased gastric motility).

Autonomic neuropathy affects the nerves that regulate vital functions, including the heart muscle and smooth muscles.

Damage to the nerves supplying blood vessels causes problems with blood pressure and body temperature.

Autonomic neuropathy is associated with the following:

• Alcoholic neuropathy
• Diabetic neuropathy
• Disorders involving scarring and hardening (sclerosis) tissues
• Guillain Barre syndrome or other diseases that inflame nerves
• HIV and AIDS
• Inherited nerve disorders
• Parkinson's disease
• Surgery or injury involving the nerves
• Use of anticholinergic medications

Symptoms

Symptoms vary depending on the nerve(s) affected. They usually develop gradually over years.

Symptoms may include:

Digestive tract

• Constipation
• Diarrhea
• Feeling full after only a few bites (early satiety)
• Nausea after eating
• Swollen abdomen
• Unintentional loss of more than 5% of body weight
• Vomiting of undigested food

Heart

• Blood pressure changes with position
• Dizziness that occurs when standing up

Urinary tract

• Difficulty beginning to urinate
• Feeling of incomplete bladder emptying
• Urinary incontinence (overflow incontinence)

Other symptoms

• Abnormal sweating
• Fainting
• Heat intolerance, induced by exercise
• Male impotence

Signs and tests

A medical history and general physical exam are critical. A brain and nervous system (neurological) examination may show evidence of injury to other nerves. However, it is very difficult to directly test for autonomic nerve damage.

Signs of autonomic neuropathy include:

• Abnormal sounds in the abdomen, indicating decreased gastric movement (motility)
• Decrease of blood pressure upon standing up (postural hypotension)
• Sluggish pupil reaction in the eye
• Swollen (distended) abdomen
• Swollen (distended) bladder

Occasionally, other symptoms may indicate a problem in the function of the autonomic nervous system, including:

• Difficulty swallowing
• Excessive sweating
• Irregular heart rhythms
• High blood pressure
• Rapid or slow heart rate

Special measurements of sweating and heart rate are called "autonomic testing" and can assist in diagnosis and treatment.

Other tests include:

• Measurement of blood pressure lying down, sitting, and standing
• Measurement of changes in heart rate
• Upper GI
• Esophagogastroduodenoscopy (EGD)
• Isotope study
• Voiding cystourethrogram (VCUG) or other tests of bladder function

Other tests for autonomic neuropathy are based on the suspected cause of the disorder, as suggested by the history, symptoms, and the way symptoms developed.

Treatment

Treatment is supportive and may need to be long-term. Several treatments may be attempted before a successful one is found.

Various strategies may be used to reduce symptoms in the feet, legs, and arms. These include:

• Florinef and salt tablets to increase fluid volume in blood vessels
• Fludrocortisone or similar medications to reduce postural hypotension
• Medications to help with salt and fluid retention
• Proamatine to prevent a drop in blood pressure when standing
• Sleeping with the head raised
• Use of elastic stockings

Treatments for reduced gastric motility include:

• Medications that increase gastric motility (such as Reglan)
• Sleeping with the head raised
• Small, frequent meals

Diarrhea, constipation, bladder problems, and other symptoms are treated as appropriate. These symptoms may respond poorly to treatment. Drugs that block bladder contractions may be used to help with urinary control problems.

Phosphodiesterase type 5 (PDE-5) drugs, such as sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are safe and effective for treating impotence in patients with diabetes.

Expectations (prognosis)

The outcome varies. If the cause can be found and treated, there is a chance that the nerves may repair or regenerate. The symptoms may improve with treatment, or they may continue or get worse, even with treatment.

Most symptoms of autonomic neuropathy are uncomfortable, but they are rarely life-threatening.

Complications

• Fluid or electrolyte imbalance such as low blood potassium (if excessive vomiting or diarrhea)
• Injuries from falls (with postural dizziness)
• Kidney failure (from urine backup)
• Malnutrition
• Psychological/social effects of impotence

Calling your health care provider

Call for an appointment with your health care provider if you have symptoms of autonomic neuropathy. Early symptoms might include:

• Becoming faint or light-headed when standing
• Changes in bowel, bladder, or sexual function
• Unexplained nausea and vomiting when eating

Early diagnosis and treatment increases the likelihood of controlling symptoms.

Prevention

Preventing or controlling disorders associated with autonomic neuropathy may reduce the risk. For example, diabetics should closely control blood sugar levels. Alcoholics should stop drinking.

References

Hunt D. American Diabetes Association (ADA). Standards of medical care in diabetes--2008. Diabetes Care. 2008;31:S12-S54.

Vardi M, Nina A. Phosphodiesterase inhibitors for erectile dysfunction in patients with diabetes mellitus. Cochrane Database Syst Rev. 2007;24(1):CD002187.

Benarroch E, Freeman R, Kaufman H. Autonomic nervous system. In: Goetz CG, eds. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 207: chap 21.