Autonomic Nervous System Testing (ANST) Laboratory Print E-mail

What is the autonomic nervous system?

The autonomic nervous system is that part of the nervous system that controls:

  • Blood pressure and pulse rate
  • Blood flow to different parts of the body
  • Sweating
  • Bowel and Bladder function
  • Sexual function

What does the test feel like?
ANS testing is made of four individual tests each measure an aspect of the ANS. All the tests are usually done in one session that lasts less thank 90 minutes. They are non invasion and safe.

  1. Sweat Test:
    For this test, small plastic capsules are attached to the arms and legs. A machine is used to stimulate the sweat glands and measures sweat production. You may feel a slight local burning or tingling during this test.
  2. Heart Rate during Deep Breathing (HRDB)Test:
    This test measures your heart rate variation during deep breathing. You will be asked to breath deeply and steadily in a rate of 6 breaths/minutes guided by a moving green light.
  3. Valsalva Test:
    During this test you blow into a plastic tube for 15 seconds hard enough to produce a pressure of 40mm/Hg as indicated in a hanging watch that you will be asked to watch. This test measures your blood pressure and heart rate response to valsalva maneuver.
  4. The Tilt Table Test:
    After lying on a table for the first part of the test, you will be raised to a nearly upright position. You will be secured to the table so you cannot fall. The test will measure your blood pressure and pulse during different positions.

What is the utility of the obtained information?
These tests will determine whether your autonomic nervous system is working normally. The results may help to make a diagnosis and to show how you will respond to certain treatments. The type of treatment will depend on the diagnosis, and your signs and symptoms.

Are there medications I should avoid before testing?
There are a number of medications that would cause the test to be inaccurate and they should be discontinued 12-24 hours before the test if permitted by the prescribing physician. They include:

  1. Common cold remedies
  2. Drugs for depression
  3. Drugs for hypertension
  4. Parkinson’s disease
  5. Drugs for pain
  6. Proamantine and Fludrocortisone

Are there other special preparations?

  1. Avoid heavy meals before the test.
  2. Avoid alcohol, caffeine or nicotine for 4 hours before the tests.
  3. Avoid vigorous exercise for 24 hours.
  4. Wear soft, non-restrictive clothing. Avoid clothing that may restrict blood flow, including stockings and corsets. Remove elastic stockings.
  5. Avoid stressful circumstances. Your test will be more successful if you are rested and relaxed.
  6. Arrive early.
  7. Evacuate your bladder before the test.
  8. Do not engage in discussion with the operator during the test because this may affect your autonomic reflexes.

What are the common signs and symptoms of damage to the autonomic nerves?

The signs and symptoms of autonomic nerve damage depend on which parts of your autonomic system are affected. They include:

  • A drop in blood pressure when you stand. This is called orthostatic hypotension. This can cause dizziness and fainting.
  • Trouble urinating. This includes diminished feeling, urine leaking from a full bladder and inability to empty your bladder completely. This can cause urinary tract infections.
  • Male impotence
  • Vaginal dryness
  • Problems with arousal and orgasm in women.
  • Problem digesting food (gastroparesis). This can cause 
    • Diarrhea
    • Constipation
    • Abdominal bloating
    • Nausea
    • Vomiting
    • Heartburn
    • Feeling full after eating small amounts of food
    • Loss of appetite
  • Cardiovascular problems, like heart rate problems
  • Heat intolerance, especially during exercise
  • Abnormal sweating (usually decreased)
  • Slow pupil reaction to light and dark
  • Exercise intolerance. This causes your heart rate to remain the same instead of increasing or decreasing due to your activity level.
  • Lack of the usual warning signs of low blood sugar (hypoglycemia), including shakiness, sweating and palpitations.

Are there medical conditions where autonomic testing should not be done, or would be unreliable?
Yes. You should not have testing done if you have: atrial fibrillation, cardiac failure, chronic obstructive pulmonary disease (COPD), or SICCA syndrome (combination of dry eyes and mouth plus diseases such as rheumatoid arthritis or scleroderma).

Who orders the test?
These tests are usually ordered by a neurologist, but may be ordered by a patient’s primary care provider.

How is the test scheduled?
Your provider can contact  The Nerve and Muscle Center of Texas at (713) 795-0033

Are the tests covered by insurance?
We will check with your insurance company to verify coverage for autonomic testing .

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