Autonomic disorders

Definition

Autonomic disorders, also called dysautonomia, are disorders of the autonomic nervous system (ANS), the part of the nervous system that controls certain activities in the body automatically without any effort from the individual. Involuntary functions such as heart beat, blood pressure , swallowing, breathing and many others are regulated by the ANS.

Description

Autonomic nervous system disorders affect many body parts, organs and body functions. The ANS controls nerves in internal organs such as the heart, lungs, blood vessels, stomach, intestines, liver, kidneys and bladder; it also controls body temperature, blood pressure, heart rate, breathing rate, metabolism and digestion, urination and bowel movements, sexual responses, eye muscles and glands that produce tears, sweat, saliva and digestive secretions.

Two main divisions of the ANS, sympathetic and parasympathetic divisions, respond to information received from the body or the body's outside environment. Chemical messengers secreted by nerve fibers (neurotransmitters acetylcholine and norepinephrine) deliver information through the autonomic nerve pathway and nerve cells in the brain, in or near the spinal cord, or in body organs. Stimulation or speeding of body processes is a task of the sympathetic division, and inhibition or slowing of processes is a parasympathetic division task. In health, the divisions work together, allowing the body to respond properly to different situations. Sexual responses, for example, are influenced by both sympathetic and parasympathetic control along with the somatic nervous system that controls transmission of skin sensations. Heart rate and blood pressure are increased by the sympathetic division and decreased by the parasympathetic, helping to maintain a consistent heart beat and stable blood pressure. In stressful situations or emergencies, the sympathetic division responds by increasing heart rate and opening (dilating) airways, as well as increasing muscle strength through the release of stored energy. Sweaty palms, dilated pupils, and hair standing on end are other responses made by the sympathetic division in emergency situations. The parasympathetic division influences ordinary body functions such as metabolism of food and nutrients, a process that stimulates the digestive tract (gastrointestinal tract) to promote digestion, assimilation of nutrients, and the excretion of waste products.

A third division of the ANS is the enteric nervous system, which is made up of nerve cells in the intestinal walls that control muscle contractions of the walls (peristalsis) to propel waste through the intestines. Intestinal motility disorders (dysmotility) may develop if parasympathetic nerve cells of the intestines or the enteric nervous system are damaged.

Dysfunction of autonomic nerves or of any division of the ANS can develop on its own, or be influenced by other conditions and diseases such as alcoholism, diabetes, atherosclerosis or tetanus.

These conditions may damage the autonomic nerves, resulting in some type of autonomic dysfunction. The whole autonomic system may be involved, producing a range of symptoms, or only part of the system may be affected. Although there is no cure for autonomic disorders, some can be corrected by treating an underlying disease, and others can be relieved by drug therapy. Some may involve progressive damage and dysfunction.

Common autonomic disorders include blood pressure abnormalities (orthostatic hypotension or pure autonomic failure), sweating disorders, complex regional pain syndromes, urinary system disorders such as urine retention and urinary incontinence , erectile dysfunction or impotence, swallowing disorders (glossopharyngeal neuralgia ), eye movement problems (oculomotor paresis), gastrointestinal or digestive disturbances, and heart rate irregularities (cardiac arrhythmia, tachycardia). Some autonomic disorders may actually begin in the peripheral or central nervous systems and may involve central nervous system activity as well as ANS activity.

Demographics

Middle aged and elderly adults of both sexes and all races may develop autonomic disorders. Typical age of onset is between ages 40 and 60. Orthostatic hypotension occurs more frequently in women than in men.

Causes and symptoms

Autonomic disorders are the result of autonomic nerve damage that can stem from known or unknown causes. Some causes of autonomic nerve damage are genetic, derived from gene patterns that may influence specific autonomic disorders (familial dysautonomia); some are a combination of genetic and environmental causes; and others are related to a degenerative condition of aging related to the loss of neurons in groups of autonomic nerve cells (ganglia). Underlying diseases and conditions that damage autonomic nerves may cause autonomic disorders; examples include diabetes, tetanus, autoimmune diseases and alcoholism.

In tetanus, the tetanus toxin in an infected wound is carried by autonomic nerve cells (neurons) to the spine where it may damage sources of autonomic control. Atherosclerosis, the presence of hard, fatty build up on blood vessel walls, can involve the carotid artery in the neck or the cervical spine at the back of the neck, resulting in Horner's syndrome, a disorder of the sympathetic nervous system. A tumor in the carotid area can press on sympathetic and parasympathetic nerve fibers, resulting in heart and blood pressure irregularities. Autonomic disorders can also occur in connection with degenerative nervous system diseases such as Parkinson's disease. Depression has been known to suppress contractions in the esophagus and colon, interfering with digestion and elimination. Injury to peripheral nerves may cause complex regional pain syndrome, a condition in which an individual experiences severe pain with simple touches to the skin such as placing a sheet or piece of clothing on the affected area. Previous spinal injuries may later result in autonomic nerve damage in addition to central nervous system injury. Ingestion of certain medications and drugs, contact with or ingestion of poisons such as insecticides or rat poison, or exposure to environmental toxins may also alter ANS functioning and can sometimes cause acute or chronic failure of the autonomic nervous system.

Symptoms vary with the body part or organ system affected by nerve damage. Some individuals have some degree of involuntary urination (incontinence) or the opposite condition, difficulty emptying the bladder (urinary retention). Men may complain of difficulty achieving or maintaining an erection. The most disabling symptom associated with autonomic disorders is reported to be dizziness on standing from a sitting or reclining position due to an abrupt change in blood pressure (orthostatic hypotension). Other possible symptoms include dry eyes and mouth, difficulty swallowing, reduced sweating, feelings of stomach fullness, vomiting, and constipation or losing control of bowel movements (fecal incontinence ). The pupils of the eyes may be of different size or may not respond to changes in light, and eye movements may be limited.

Diagnosis

The doctor will take a careful history of previous illnesses and surgeries, current and prior medications, injuries, environmental exposures, and a family health history . A physical examination usually reveals signs and symptoms of autonomic disorders. The eyes are examined for pupil size, movement and responses to changes in light. Speech and ability to swallow may be checked. Body temperature is taken. Blood pressure is measured and measurements between sitting and standing are compared. Electrocardiography (ECG) is sometimes performed to evaluate heart rate changes during deep breathing or forceful exhale as in moving the bowels (Valsalva maneuver). If Horner's syndrome is suspected, x rays or magnetic resonance imaging (MRI) may be ordered to examine the carotid artery and the cervical discs of the spine. Nervous system functioning is usually tested using the quantitative sudomotor axonreflex test. Sweat tests are performed by stimulating sweat glands and measuring volume of sweat to indicate effectiveness of production. The ability of the anal sphincter muscle to contract normally is tested by an anal wink reflex test that involves scratching skin near the anus. Laboratory tests done to evaluate general health include a complete blood count (CBC) and specific blood chemistries such as electrolytes (e.g., sodium , potassium, calcium ) blood glucose and liver enzymes. A urinalysis is performed on a single urine specimen to determine kidney function, and a 24-hour urine test may be done to determine if urine output is normal.

Treatment

Treatment of autonomic disorders may involve treating an underlying disease. If there are no underlying conditions or the underlying illness can not be treated or managed, symptom relief is the goal of treatment. Drug therapy is common for autonomic disorders affecting the stomach and intestines, including metoclopramide that stimulates contractions of the stomach and intestines to help move food and waste through more quickly. Motility throughout the digestive tract, from the esophagus to the colon, may be improved when antidepressants are given. When limited intestinal contractions result in constipation, fiber supplements and stool softeners are often used to speed intestinal waste product movement. Urinary incontinence is treated by drugs that relax the muscles of the bladder (oxybutin, tolterodine), and urinary retention can be treated by drugs that stimulate bladder contractions and ease release of urine (bethanechol).

Several drugs are effectively used to restore erectile function (sildenafil, tadalafil, vardenafil) when there are no other complicating factors such as prostate enlargement or cancer . Drugs that help the body balance sodium and potassium to regulate blood volume and blood pressure can relieve orthostatic hypotension (fludrocortisone, midodrine), and another drug, pyridostigmine, helps maintain blood pressure during standing, but does not increase pressure when an individual lies down. Ongoing research to identify genes and gene functions involved in autonomic disorders may lead to more specific and effective drug therapies for autonomic disorders.

Complex regional pain syndrome is not always relieved by pain medications and may require a procedure to block damaged sympathetic nerves in the affected region.

QUESTIONS TO ASK YOUR DOCTOR

• Can I recover from this condition?
• Will my symptoms improve or go away?
• Are there medications to relieve my symptoms?
• How often do you see this kind of nervous system disorder?
• How many of your patients with this condition recover?

Nutrition/Dietetic concerns

Individuals with orthostatic hypotension are often encouraged to drink more water and increase salt intake to help maintain blood volume and stabilize blood pressure. For digestive problems, a high-fiber diet with whole grains, whole fruit and leafy greens is recommended to bulk the stool and encourage normal contractions of the intestines. A soft or mechanical diet with mashed or chopped foods may be required for individuals who have difficulty swallowing or whose stomach secretions do not break up food sufficiently. Fluid intake, especially water and clear fluids, is essential for individuals with dry mouth and eyes, while fluids that dehydrate such as coffee and alcohol should be avoided.

Therapy

Some autonomic disorders respond to treatment methods that involve physical therapy or the use of supportive devices to aid or restore function. Individuals with orthostatic hypotension are urged to stand up slowly and to wear a support garment such as abdominal binder, body compression suit or compression stockings. Elevating the head of the bed several inches may also help blood circulate during sleep and cause less of a change in blood pressure on waking and standing. When sweating is reduced or absent because of an autonomic disorder, warm environments and overheating should be avoided. Individuals with urine retention can often be instructed in the use of catheters to help empty the bladder regularly.

Prognosis

There is no cure for autonomic disorders. However, if an underlying condition or disease can be corrected or managed, autonomic disorders may be corrected or controlled as well, reducing symptoms. Autonomic disorders that are not directly related to an underlying condition may involve progressive autonomic nerve damage and worsening of symptoms. Autonomic disorders that affect heart rate, breathing rate and blood pressure can become life threatening.

KEY TERMS

Arrythmia —Loss of the normal rhythm of the heart beat.

Dysmotility —Reduced or absent movement of the intestinal walls for the purpose of propelling food and waste through the intestines.

Electrocardiography —A method used to trace and record the heart's electrical activity in order to evaluate heart function.

Ganglia —Groups of nerve cell bodies in the peripheral nervous system. Also referred to as neuroganglion.

Neuron —A small component of the nervous system composed of a nerve cell body with branch-like processes called dendrites and an axon that conducts nerve impulses. Also referred to as a neurocyte.

Neurotransmitter —A chemical messenger secreted by nerve fibers. Neurotransmitters communicate between nerve cells, influencing the nervous system's response to information from the body or the body's outside environment.

Orthostatic —A term that describes standing erect. Orthostatic hypotension is low blood pressure that occurs in some people on standing up.

Peristalsis —Wave-like movements of the intestine that propel food and waste toward the colon and rectum for elimination.

Somatic nervous system —The part of the nervous system that controls voluntary motions and sensations of the skin.

Tachycardia —An abnormally rapid beating of the heart. The heart rate can be as high as 100 beats per minute or more.

Valsalva maneuver —Forced expiration or breathing out of air when the airway is closed. It is used to test the heart's response to changes in pressure.

Prevention

Since causes are not always known, no preventive methods for autonomic disorders are currently recommended. Careful avoidance of known toxins and poisons can reduce chances of nerve damage and autonomic disorders. Individuals with diabetes, infectious diseases , autoimmune diseases and other nervous system conditions should follow physician recommendations and take medications as prescribed to avoid possible involvement of the autonomic nervous system.

Caregiver concerns

Falling may be a concern if the patient experiences orthostatic hypotension with dizziness on standing up from a seated or prone position. Individuals who have difficulty swallowing must be observed at mealtimes so there is no danger of choking. When either urinary or fecal incontinence becomes a problem for the care giver, family members or the patient, help and advice is available from healthcare professionals and community homecare organizations. If the patient is experiencing anxiety or depression because of activity limitations related to symptoms, the physician should be informed.

Resources

BOOKS

“Autonomic Nervous System.” Merck Manual Professional Edition, edited by R. S. Porter. Whitehouse Station, NJ: Merck Research Laboratories, 2007.

“Autonomic Nervous System Disorders.” Merck Manual Home Edition, edited by R. S. Porter. Whitehouse Station, NJ: Merck Research Laboratories, 2007.

Saper, C. B. “Autonomic Disorders and Their Management.” Cecil Medicine, edited by Goldman et al. 23rd ed. Philadelphia: Saunders 2007.

ORGANIZATIONS

Dysautonomia Foundation, 315 W 39th St, Suite 701, New York, NY, 10018, (212) 279-1066, (212) 279-2066, [email protected], http://www.familialdysautonomia.org.

National Dysautonomia Research Foundation, PO Box 301, Red Wing, MN, 55066-0301, (651) 267-0525, (651) 267-0524.

L. Lee Culvert