Autonomic Nervous System Diseases

Definition

Definition of Autonomic Nervous System Diseases
The autonomic nervous system (ANS) is a very complex, multifaceted neural network that maintains internal physiologic homeostasis. This network includes cardiovascular, thermoregulatory, gastrointestinal (GI), genitourinary (GU), and ophthalmologic (pupillary) systems (see the following image). Given the complex nature of this system, a stepwise approach to autonomic disorders is required for proper understanding.

Symptoms

Symptoms of Autonomic Nervous System Diseases
In men, difficulty initiating and maintaining an erection (erectile dysfunction) can be an early symptom of an autonomic disorder. Autonomic disorders commonly cause dizziness or light-headedness due to an excessive decrease in blood pressure when a person stands (orthostatic hypotension).

People may sweat less or not at all and thus become intolerant of heat. The eyes and mouth may be dry.

After eating, a person with an autonomic disorder may feel prematurely full or even vomit because the stomach empties very slowly (gastroparesis). Some people pass urine involuntarily (urinary incontinence), often because the bladder is overactive. Other people have difficulty emptying the bladder (urine retention) because the bladder is underactive. Constipation may occur, or control of bowel movements may be lost.

Causes

Causes of Autonomic Nervous System Diseases
The etiology of autonomic dysfunction can be primary or idiopathic and secondary causes. Autonomic failure is seen in multiple system atrophy, pure or progressive autonomic failure, Parkinson and other neurodegenerative diseases, metabolic diseases such as Wernicke and cobalamin deficiency, diabetes mellitus, hyperlipidemia, trauma, vascular diseases, neoplastic diseases, and multiple sclerosis. In addition, autonomic dysfunction is associated with various medications.

In addition to diabetes, autonomic dysfunction is associated with other neuropathies, including Guillain-Barr é syndrome, Lyme disease, human immunodeficiency virus (HIV) infection, leprosy, acute idiopathic dysautonomia, amyloidosis, porphyria, uremia, and alcoholism. Besides nerve localization in the peripheral nervous system, it occurs in diseases of the presynaptic neuromuscular junction such as botulism and myasthenic syndrome.

In addition to the acquired causes, inherited disorders like hereditary sensory-autonomic neuropathy (HSAN), familial amyloid polyneuropathy (FAP), Tangier disease, and Fabry disease also exist.

Diagnosis

Diagnosis of Autonomic Nervous System Diseases
Doctors can check for signs of autonomic disorders during the physical examination. They measure blood pressure and heart rate while a person is lying down or sitting and after the person stands. They examine the pupils for abnormal responses or lack of response to changes in light.

Other tests can provide additional information. Tilt table testing may be done to check blood pressure and heart rate responses to changes in position (see Diagnosis of Heart and Blood Vessel Disorders: Tilt Table Testing). Blood pressure is measured after the person, who is lying flat on a pivoting table, is tilted into an upright position. Blood pressure is also measured continuously while the person performs a Valsalva maneuver (forcefully trying to exhale without letting air escape, as during a bowel movement). Electrocardiography is done to determine whether the heart rate changes as it normally does during deep breathing and the Valsalva maneuver.

Treatment

Treatment of Autonomic Nervous System Diseases
Disorders that may be contributing to the autonomic disorder are treated. If no other disorders are present or if such disorders cannot be treated, the focus is on relieving symptoms.

Simple measures can help relieve some symptoms:

1. Orthostatic hypotension: People are advised to elevate the head of the bed by about 4 inches (10 centimeters) and to stand up slowly. Wearing a compression or support garment, such as an abdominal binder or compression stockings, may help. Consuming more salt and water helps maintain blood volume and thus blood pressure. Sometimes drugs (midodrine, pyridostigmine, or fludrocortisone taken by mouth) are used.
2. Decreased or absent sweating: If sweating is reduced or absent, avoiding warm environments is useful.
3. Urinary retention: If urinary retention is caused by inability of the bladder to contract normally, people can be taught to insert a catheter into the bladder themselves. They insert it several times a day and remove it after the bladder is empty. Bethanechol can be used to increase bladder tone and thus ease bladder emptying.
4. Constipation: A high-fiber diet and stool softeners are recommended. If constipation persists, enemas may be necessary.
5. Erectile dysfunction: Usually, treatment consists of drugs such as sildenafil, tadalafil, or vardenafil taken by mouth.

Prognosis

Prognosis of Autonomic Nervous System Diseases
Consult with your doctor.

Prevention

Prevention of Autonomic Nervous System Diseases
Consult with your doctor.