Patient Information

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

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

What does the test feel like?
ANS testing is comprised of four individual tests, each measuring a different aspect of the autonomic nervous system.  All the tests are usually done in one session that lasts less than 90 minutes. They are non-invasive 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 measure sweat production.  You may feel a slight local burning or tingling during this test.
  2. Heart Rate during Deep Breathing Test (HRDB):
    This test measures your heart rate variation during deep breathing. You will be asked to breathe deeply and steadily at 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 by 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 will not 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.  Dr. Shaibani will review your medication list.

Are there any special preparations?

  1. Avoid heavy meals before the test.
  2. Avoid alcohol, caffeine and nicotine for 4 hours before the test.
  3. Avoid vigorous exercise for 24 hours prior.
  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. Empty your bladder before the test.
  8. Do not engage in discussion with the operator during the test because this may affect your autonomic reflexes.
  9. Do not have any lotion or cream on your skin.  Do not shave legs 24 hours   prior to the test.

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 the inability to empty your bladder completely.  This can cause urinary tract infections.
  • Male impotence
  • Vaginal dryness
  • Problems with arousal and orgasm in women
  • Problems 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.  These conditions: Atrial Fibrillation, Cardiac Failure, Chronic Obstructive Pulmonary Disease (COPD).  A pacemaker also invalidates part of the test.

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.