Tests For Autonomic Neuropathy

Today's post from mayoclinic.org (see link below) is the first of two posts from the Mayo Clinic regarding that most mysterious, yet very common form of neuropathy: Autonomic neuropathy. Autonomic means affecting parts of your body that are out of your control and behave instinctively and automatically. We take them for granted but if the nerves in these areas are damaged then the consequences can be serious and lead of a dramatic drop in the quality of life. Testing for this form of neuropathy is not taken for granted: many doctors first ascertain nerve damage of some sort and then, based on the patient's own symptoms and story, conclude that autonomic functions are also being affected. However, there are tests which can both confirm the diagnosis and measure the extent of its effect on the system. This useful, short article gives you an idea of what you can expect and maybe ask for.

Autonomic neuropathy: Tests and diagnosis
By Mayo Clinic Staff June 2015

Autonomic neuropathy is a possible complication of a number of diseases, and the tests you'll need often depend on your symptoms and 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) and have symptoms of the condition, extensive testing may not be necessary. Your doctor may perform a physical exam and ask about your symptoms.

If you are undergoing cancer treatment with a drug known to cause nerve damage, your doctor will check for signs of neuropathy.
When you don't have risk factors for autonomic neuropathy

If you have symptoms of autonomic neuropathy but don't have risk factors, the diagnosis may be more involved. Your doctor will probably review your medical history, discuss your symptoms and do a physical exam.

Your doctor may perform tests to evaluate autonomic functions, which may include: 

Breathing tests. These tests measure how your heart rate and blood pressure respond during exercises such as forcefully exhaling (Valsalva maneuver).
Tilt-table test. This test monitors the response of blood pressure and heart rate 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 narrows blood vessels and increases heart rate to compensate for the drop in blood pressure. This response may be slowed or abnormal if you have autonomic neuropathy.
A simpler way test for this response involves standing for a minute, then squatting for a minute and then standing again while blood pressure and heart rate are monitored.

Gastrointestinal tests. Gastric-emptying tests are the most common tests to check for digestive abnormalities such as slow digestion and delayed emptying of the stomach (gastroparesis). These tests are usually done by a doctor who specializes in digestive disorders (gastroenterologist). 

Quantitative sudomotor axon reflex test. 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 the response of your nerves and sweat glands. 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. While lying in a chamber with slowly increasing temperature, digital photos document the results as you begin to sweat. Your sweat pattern may help confirm a diagnosis of autonomic neuropathy or suggest 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. 

http://www.mayoclinic.org/diseases-conditions/autonomic-neuropathy/basics/tests-diagnosis/con-20029053