Autonomic neuropathies are disorders affecting the peripheral nerves that particularly damage the nerves that automatically (without conscious effort) regulate body processes (autonomic nerves).
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 autonomic nerves, which automatically (unconsciously) regulate body processes. Peripheral nerves also include somatic nerves, the nerves that 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.
Common causes include diabetes, amyloidosis (accumulation of an abnormal protein in tissues), and autoimmune disorders (when the immune system misinterprets the body's tissues as foreign and attacks them). Viral infections may trigger an autoimmune reaction that results in destruction of autonomic nerves. Some of the 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. A similar reaction often occurs in Guillain-Barré syndrome. Other causes include cancer, drugs, excessive alcohol consumption, and toxins.
A common symptom is an excessive decrease 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 (gastroparesis). Severe constipation may occur.
When somatic nerves are damaged, people may lose sensation or feel a tingling (pins-and-needles) sensation in the hands and feet, or muscles may become weak.
Diagnosis and Treatment
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 done to check for antibodies to acetylcholine receptors, which indicate an autoimmune reaction. About one half of people with an autonomic neuropathy due to an autoimmune reaction have these antibodies.
The cause, if identified, is treated. Neuropathies due to an autoimmune reaction are sometimes treated with drugs that lessen the reaction, such as azathioprine, cyclophosphamide, or prednisone. If symptoms are severe, immune globulin (a solution containing many different antibodies collected from a group of donors) may be given intravenously, or plasma exchange (plasmapheresis) may be done. In plasmapheresis, blood is withdrawn, filtered to remove abnormal antibodies, then returned to the person.
Last full review/revision November 2006 by Phillip Low, MD