Autonomic Neuropathies - Autonomic Neuropathies - Merck Manual Consumer Version (original) (raw)

Autonomic neuropathies are disorders affecting the peripheral nerves that automatically (without conscious effort) regulate body processes (autonomic nerves).

• Causes include diabetes, amyloidosis, autoimmune disorders, cancer, excessive alcohol consumption, and certain drugs.
• People may feel light-headed when they stand and have urination problems, constipation, and vomiting, and men may have erectile dysfunction.
• Doctors do a physical examination and various tests to check for autonomic malfunction and possible causes.
• The cause is corrected or treated if possible.

(See also Overview of the Autonomic Nervous System.)

The nervous system has central and peripheral parts. The central nervous system includes the brain and spinal cord. The peripheral nervous system includes the nerves that connect the body’s tissues with the brain and spinal cord. Peripheral nerves include the following:

• Autonomic nerves, which automatically (unconsciously) regulate body processes
• Somatic nerves, which connect with muscles under voluntary (conscious) control or with sensory receptors in the skin.

Autonomic neuropathies are a type of peripheral neuropathy, a disorder in which peripheral nerves are damaged throughout the body. In autonomic neuropathies, there is much more damage to the autonomic nerves than to the somatic nerves.

Causes of Autonomic Neuropathies

Common causes of autonomic neuropathies include

• Diabetes
• Amyloidosis (accumulation of an abnormal protein in tissues)
• Autoimmune disorders (when the immune system misinterprets the body’s tissues as foreign and produces antibodies that attack those tissues)

Viral infections may trigger an autoimmune reaction that results in destruction of autonomic nerves.

Some of the antibodies produced by the immune system attack the surface of a nerve fiber or the tissues that wrap around the fiber and enable it to conduct impulses quickly and accurately. (These tissues are called the myelin sheath.)

Sometimes antibodies produced by the immune system attack acetylcholine receptors (the part of nerve cells that enables them to respond to acetylcholine). Acetylcholine is one of the chemical messengers (neurotransmitters) used to communicate within the autonomic nervous system.

Other causes of autonomic neuropathies include cancer and drugs (including alcohol in excessive amounts and toxins).

Symptoms of Autonomic Neuropathies

A common symptom of autonomic neuropathies is

• An excessive drop in blood pressure when the person stands (orthostatic hypotension)

As a result, the person feels light-headed or as if about to faint.

Men may have difficulty initiating and maintaining an erection (erectile dysfunction). Some people involuntarily pass urine (urinary incontinence), often because the bladder is overactive. Other people have difficulty emptying the bladder (urine retention) because the bladder is underactive. After eating, some people feel prematurely full or even vomit because the stomach empties slowly (called gastroparesis). Severe constipation may occur.

When somatic nerves are also damaged, people may lose sensation or feel a tingling (pins-and-needles) sensation in the hands and feet, or muscles may become weak.

Diagnosis of Autonomic Neuropathies

• A doctor's evaluation
• Sometimes blood tests

Doctors may suspect an autonomic disorder based on symptoms. A physical examination and certain tests are done to check for signs of autonomic disorders and possible causes (such as diabetes or amyloidosis).

Blood tests are sometimes done to check for antibodies to acetylcholine receptors, which indicate an autoimmune reaction. About half of people with an autonomic neuropathy due to an autoimmune reaction have these antibodies.

Treatment of Autonomic Neuropathies

• Treatment of the cause if identified
• Sometimes immunosuppressants
• For severe symptoms, sometimes immune globulin or plasma exchange

If symptoms of autoimmune autonomic neuropathy are severe, immune globulin (a solution containing many different antibodies obtained from the blood of people with a normal immune system) may be given intravenously, or plasma exchange may be done. In plasma exchange, blood is withdrawn, filtered to remove abnormal antibodies, then returned to the person.