Tests and diagnosis

By Mayo Clinic Staff

Autonomic neuropathy is a possible complication of a number of diseases, and the tests you'll need often depend on whether or not you have known risk factors for autonomic neuropathy.

When you have known risk factors for autonomic neuropathy

If you have conditions that increase your risk of autonomic neuropathy, such as diabetes, your doctor can often make the diagnosis based on your signs and symptoms. Similarly, if you have cancer and it's being treated with a drug known to cause nerve damage, your doctor will be on the lookout for signs of neuropathy.

When you don't have risk factors for autonomic neuropathy

If your symptoms point to autonomic neuropathy and you're unaware of an underlying cause, the diagnosis is more difficult. Your doctor is likely to review your medical history, ask for a thorough description of your symptoms and do a physical exam. Tests that your doctor may use to help with diagnosis will evaluate the reaction of several body functions controlled by the autonomic nervous system. These may include:

  • Breathing tests. These tests measure how your heart rate and blood pressure respond to breathing exercises such as the Valsalva maneuver, in which you exhale forcibly.
  • Tilt-table test. This test monitors how your blood pressure and heart rate respond to changes in posture and position, simulating what occurs when you stand up after lying down. You lie flat on a table, which is then tilted to raise the upper part of your body. Normally, your body compensates for the drop in blood pressure that occurs when you stand up by narrowing your blood vessels and increasing your heart rate. This response may be slowed or abnormal if you have autonomic neuropathy. A simpler way to test for postural changes in blood pressure involves standing for a minute, then squatting for a minute and then standing again. Blood pressure and heart rate are monitored throughout this test.
  • Gastrointestinal tests. Gastric-emptying tests are the most common tests to check for slowed movement of food through your system, delayed emptying of the stomach and other abnormalities. These tests are usually done by a doctor who specializes in digestive disorders (gastroenterologist).
  • Quantitative sudomotor axon reflex test (QSART). This test evaluates how the nerves that regulate your sweat glands respond to stimulation. A small electrical current passes through four capsules placed on your forearm, foot and leg, while a computer analyzes how your nerves and sweat glands react. You may feel warmth or a tingling sensation during the test.
  • Thermoregulatory sweat test. During this test, you're coated with a powder that changes color when you sweat. You then enter a chamber with slowly increasing temperature, which will eventually make you perspire. Digital photos document the results. Your sweat pattern may help confirm a diagnosis of autonomic neuropathy or other causes for decreased or increased sweating.
  • Urinalysis and bladder function (urodynamic) tests. If you have bladder or urinary symptoms, a series of urine tests can evaluate bladder function.
  • Ultrasound. If you have bladder symptoms, your doctor may do an ultrasound, in which high-frequency sound waves create an image of the bladder and other parts of the urinary tract.
July 12, 2012

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