Autonomic Neuropathy -Causes, Signs and symptoms

Autonomic Neuropathy

Also called: Autonomic Nerve Damage, Visceral Nerve Damage, Visceral Neuropathy

Summary

Autonomic neuropathy describes the symptoms that occur when nerves of the autonomic nervous system (ANS) have been damaged. The ANS regulates involuntary functions of the body such as heart rate, blood pressure, digestion and perspiration. Although autonomic neuropathy affects the internal organs and patients may experience discomfort, the condition is rarely life-threatening.

Autonomic neuropathy often results from diabetes. Experts do not completely understand how diabetes damages nerves, but high blood sugar is believed to be a likely cause. Many other health disorders are also associated with autonomic neuropathy.

Patients with autonomic neuropathy may experience a number of symptoms related to their condition. These include a tendency to experience rapid drops in blood pressure upon standing (orthostatic hypotension), as well as urinary, cardiovascular and digestive problems. They may also develop an intolerance to heat. 

Autonomic neuropathy may be difficult to diagnose, as other conditions that cause similar symptoms must first be ruled out. Various tests may help a physician confirm a diagnosis. In many cases, treatment of autonomic neuropathy focuses on treating the underlying disorder that is causing symptoms, such as diabetes, Parkinson’s disease or an autoimmune disorder. Medications also can treat symptoms and complications associated with autonomic neuropathy.

Autonomic neuropathy usually cannot be prevented. Nevertheless, people can take steps to reduce their vulnerability to this condition, such as controlling diabetes, exercising regularly and avoiding smoking.

About autonomic neuropathy

Autonomic neuropathy is damage to the nerves of the autonomic nervous system (ANS). It is a type of neuropathy, which is the term used for damage, disease or inflammation to the nerves of the body. Autonomic neuropathy is considered to be a collection of symptoms rather than a specific disease.

The body’s nervous system is divided into two parts. The central nervous system (CNS) is made up of the brain and spinal cord. The peripheral nervous system (PNS) includes nerves that extend from the CNS to the rest of the body. The PNS itself is also divided into two systems. One part of the PNS, the somatic nervous system, is under conscious control and is activated when a person wishes to move a body part. The somatic nervous system also processes the information received from the senses. The other part of the PNS is the ANS.

The ANS regulates involuntary functions of the body such as heart rate, blood pressure, digestion, respiration (breathing), genital and urinary functioning and perspiration. In a healthy body, ANS nerves transmit messages between the brain and the blood vessels, skin and internal organs. Damage to the nerves of the ANS can short-circuit these messages, preventing them from being sent or causing them to be sent too slowly or at the wrong time. For example, a patient who experiences damage to ANS nerves in the gastrointestinal tract is likely to have problems properly digesting food. This can lead to symptoms such as abdominal bloating, constipation, diarrhea, nausea and vomiting.

Numerous complications are associated with autonomic neuropathy. Sudden drops in blood pressure may cause patients to faint, which can lead to fall-related injuries. Low blood pressure can also cause mental and physical fatigue. Digestive system difficulties can result in malnutrition, weight loss, or fluid or electrolyte imbalances such as hypokalemia (insufficient potassium levels).

The prognosis for patients with autonomic neuropathy varies. Some patients may notice improvement over time while others may experience a worsening of their condition despite treatment. Although symptoms associated with autonomic neuropathy are often uncomfortable, they are rarely life-threatening. However, damage to autonomic nerves can be potentially fatal if it impairs functions such as breathing or normal heartbeat.

Risk factors/causes of autonomic neuropathy

There are numerous conditions and diseases that can cause autonomic neuropathy, including:

  • Parkinson’s disease
  • Multiple system atrophy 
  • Autoimmune diseases
  • Alcoholism
  • Amyloidosis (abnormal buildup of protein in the organs)
  • Injury or surgery involving the nerves
  • Disorders involving a hardening of body tissue
  • Medication use (e.g., anticholinergics, chemotherapy drugs)
  • Tumors

One of  the most significant risk factors for autonomic neuropathy is diabetes. The longer a person has the disease, the greater the risk of neuropathy. People with the greatest vulnerability include those who are older than 40, have had diabetes for more than 25 years and who have difficulty controlling their blood sugar.

Other factors that increase the risk of developing autonomic neuropathy include:

  • Excessive body weight
  • High blood pressure
  • High levels of blood fat
  • Smoking

Signs and symptoms of autonomic neuropathy

Patients with autonomic neuropathy may experience a number of symptoms related to their condition. Symptoms may be mild to severe and can vary from person to person, depending on which nerves are damaged.

One of the most common groups of symptoms associated with autonomic neuropathy results from damage to nerves that affect blood vessels. People who have damage to these nerves may experience blood pressure and body temperature abnormalities. For example, patients may experience a rapid drop in blood pressure upon standing (orthostatic hypotension), which can lead to dizziness and fainting. Furthermore, some patients may find that their heart rate does not adjust appropriately during physical exertion. High blood pressure can also result from damage to the nerves that supply blood vessels. 

Additionally, if blood vessels of the skin are not able to dilate effectively to reduce body heat, it can result in a reduced ability to sweat, which can lead to overheating and heat stroke. In some cases, ANS nerve damage may cause extreme sweating at night or while eating.

Additional symptoms associated with autonomic neuropathy include:

  • Bladder and bowel dysfunction. People with autonomic neuropathy may experience difficulty emptying their bladder (urinating) or bowel (defecating). This may lead to conditions such as urinary tract infections and urinary or fecal incontinence.
  • Sexual problems. Men may experience impotence, while women may experience vaginal dryness and difficulties becoming aroused or achieving orgasm.
  • Gastrointestinal problems. A wide range of symptoms can result from nerve damage to the gastrointestinal system, including symptoms associated with gastroparesis (delayed gastric emptying). Symptoms may include constipation, nausea, vomiting, abdominal bloating, loss of appetite and early satiety (feeling of fullness). Other parts of the gastrointestinal system may also be damaged. For example, nerve damage affecting the esophagus may cause difficulty swallowing and nerve damage affecting the intestines may cause diarrhea.
  • Lack of indicators of hypoglycemia (low blood sugar). Patients may not display the signs that typically accompany this condition, such as shakiness, sweating and palpitations. In people who have diabetes, this may make the condition difficult to manage.
  • Poor performance of the pupils in the eye. Pupils may react sluggishly to changes in light or dark.

Symptoms of autonomic neuropathy may be uncomfortable, but are rarely life-threatening.

Diagnosis methods for autonomic neuropathy

In diagnosing autonomic neuropathy, a physician is likely to perform a physical examination and compile a medical history of the patient. Autonomic neuropathy may be difficult to diagnose because many of its symptoms are similar to those of other medical conditions.

A physician will start by looking for physical signs that may indicate autonomic neuropathy. This may include abdominal distention or abdominal sounds that indicate decreased movement of food through the digestive tract. An examination of the eyes may indicate sluggishness in pupil reaction. Patients will likely be asked about their symptoms, including their ability to sweat, urinate or have regular bowel movements.

A physician may also conduct autonomic testing, which are a group of tests designed to measure a patient’s heart rate, blood pressure and flow, skin temperature and ability to sweat. Autonomic testing may include:

  • Breathing tests. These tests record heart rate and blood pressure in response to breathing exercises. For example, a patient may be asked to take deep breaths for a minute or blow into a tube to increase pressure in the chest (the Valsalva maneuver).

  • Tilt-table test. The patient lies on a table that is tilted to raise the upper part of the body. This stresses the autonomic nervous system (ANS), and the ANS response is measured through blood pressure and heart rate. Lower than normal rates may indicate autonomic neuropathy.

  • Thermoregulatory sweat test. The patient is coated with a special powder and then asked to enter a chamber. As the temperature inside the chamber is increased, the powder on the patient changes color in response to perspiration. Abnormal perspiration activity may indicate autonomic neuropathy.

  • Quantitative sudomotor axon reflex test (QSART). This may be used to measure a patient’s ability to sweat. Electrodes are placed on the patient’s arms and/or legs. Then, a small electrical current is passed through the electrodes to activate the ANS nerves that affect a person’s sweat glands to induce sweating.

An important element in the diagnosis of autonomic neuropathy is ruling out other conditions that may have similar symptoms. Additional tests that may be used in this manner include:

  • Barium contrast studies. X-rays of the gastrointestinal tract are taken after a patient has consumed a special liquid (barium). This test may be used to identify physical obstruction or other abnormalities within the digestive tract that may be causing the patient’s gastrointestinal symptoms.

  • Radionuclide imagingSpecial radioactive chemicals are introduced into the patient’s body and then imaging tests are conducted in order to identify changes in size, shape, position or function of internal organs. This type of test may be performed to identify abnormal gastric movement, which may indicate autonomic neuropathy or other conditions.

  • Esophagogastroduodenoscopy (EGD). Also called an upper endoscopy, this test is performed by inserting a small, flexible tube with an attached camera through the mouth and into the digestive tract (after a patient has been sedated). This test may identify other causes of a patient’s gastrointestinal symptoms.

  • Ultrasound. Uses high frequency sound waves to produce an image of the bladder and other parts of the urinary tract, which are then analyzed for irregularities.

  • Bladder function tests. These may include a voiding cystourethrogram (VCUG), in which x-rays are taken as the bladder fills and empties. Bladder function tests may indicate whether a patient’s bladder can effectively contract and empty.  

Additional diagnostic tests may be warranted, depending on the suspected cause of a patient’s symptoms.

Treatment options for autonomic neuropathy

In many cases, treatment of autonomic neuropathy focuses on treating the underlying disorder that is causing a patient’s symptoms such as diabetes, Parkinson’s disease or autoimmune disorders. Depending on the medical condition involved, treatment may be needed for the rest of a patient’s life.

Treatment may also focus on alleviating the symptoms of autonomic neuropathy. This may include medications to treat complications and symptoms such as urinary tract infections, gastrointestinal problems, orthostatic hypotension, sexual dysfunction and sweating problems. Early diagnosis and treatment may improve the likelihood of being able to control a patient’s symptoms.

People who have trouble emptying their bladder may be asked to undergo periodic urinary catheterization. In this procedure, a tube is placed in the urethra to help empty the bladder. This can help lower the risk of developing urinary tract infections.

Patients also may be urged to take various self-care measures to help relieve symptoms. Patients who have trouble digesting foods may be advised to eat several smaller meals rather than three large meals. Avoiding fats and reducing dietary fiber also may aid digestion. Drops in blood pressure upon standing can be relieved by wearing elastic stockings and sleeping with the head elevated. Any changes in posture (e.g., rising from a sitting or lying position) should be made slowly.

Prevention methods for autonomic neuropathy

In most cases, autonomic neuropathy cannot be prevented because of the nature of the underlying cause. For example, there is no way to prevent degenerative diseases such as multiple system atrophy that can cause autonomic neuropathy.

People with diabetes can reduce their risk of nerve damage by closely controlling their blood sugar levels. Research has found that the higher a person’s blood sugar levels, the greater the odds of experiencing nerve damage.

Other methods of preventing autonomic neuropathy include:

  • Avoiding smoking
  • Exercising regularly
  • Maintaining a healthy weight level
  • Not drinking excessive amounts of alcohol
  • Seeking treatment for disease that cause autonomic neuropathy, such as autoimmune disorders.

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following questions related to autonomic neuropathy:

  1. What are the first symptoms of autonomic neuropathy that I am likely to notice?
  2. How will you diagnose my autonomic neuropathy?
  3. What is the likely cause of my autonomic neuropathy?
  4. Do I need to be tested for diabetes?
  5. How fast is my autonomic neuropathy likely to progress?
  6. What are my treatment options?
  7. What are the side effects of these treatments?
  8. Are there self-care steps that I can take to reduce my symptoms?
  9. What signs should I look for that might indicate my condition is worsening?
  10. What is my long-term prognosis?
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