Autonomic neuropathy: Tests and diagnosis - MayoClinic.com<
Autonomic neuropathy: Tests and diagnosis - MayoClinic.com
By Mayo Clinic Staff
April 15, 2008
Tests and diagnosis
Autonomic neuropathy is a possible complication of several diseases. You'll most likely be getting medical care for diabetes, for example, before you develop signs and symptoms suggesting autonomic neuropathy, so the diagnosis will be fairly straightforward. 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.
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 aid in diagnosis will help to 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.
* Gastrointestinal tests. Gastric emptying tests are the most common test to check for slowed movement of food through your system, delayed emptying of the stomach and other abnormalities. The testing can take various forms. One test may measure the rate at which food leaves your stomach, while another checks how well your stomach muscles relax after you eat.
* 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. It causes your body temperature to increase 1 to 1.5 degrees Celsius, which makes most people sweat. 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. 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.
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