Autonomic Testing
The autonomic nervous system is made up of a network of nerves that extend throughout the body. These nerves work together with a variety of organs to help regulate control of some of the body functions that we do not consciously control, such as: breathing, heart rate, blood pressure, sweating, body temperature, digestion etc.
Autonomic testing comes in a variety of forms and one of those is to have something called an autonomic reflex screen done. This screen gives a general overview of sweating function, heart rate function and blood pressure function.
Some of the same testing can be used to help assess a pain condition known as Complex Regional Pain Syndrome (CRPS) or Reflex Sympathetic Dystrophy (RSD).
There are many diseases that can affect the autonomic nervous system ranging from disorders affecting small nerve fibers (diabetes, amyloidosis etc.), autoimmune or inflammatory conditions (autoimmune autonomic ganglionopathy, Guillain-Barré syndrome etc.), postural orthostatic tachycardia syndrome (POTS), congenital or genetic conditions, infections (HIV, Lyme, Chagas etc.), toxins (alcohol, botulinum toxin, tetanus etc.), trauma (especially if there is spinal cord damage), tumors or even degenerative diseases such as Multiple System Atrophy, Parkinson disease or Pure Autonomic Failure.
Autonomic Reflex Screen
The autonomic reflex screen consists of a quantitative sudomotor axon reflex test (QSART), Valsalva analysis, heart rate variability to deep breathing and a tilt table test.
The QSART consists of applying some specialized capsules on the skin, followed by the application of a solution of acetylcholine and a light electrical stimulation for iontophoresis of the solution into the skin. The machine then records the sweat response that follows. There is one capsule applied to the forearm, two to your leg and one over your foot.
Valsalva analysis involves having a special blood pressure monitor attached to your fingers/hand and then having you force air into a special valve. This generates pressure which causes changes in blood pressure and heart rate. These are recorded for later analysis.
Heart rate variability to deep breathing involves you performing some directed rhythmic deep breathing, while devices record changes in your heart rate for analysis.
The tilt table test is done at the end with you strapped, for your safety, onto a table which can then tilt upwards to 70 degrees. Then your heart rate, blood pressure and symptoms are monitored for about 10 minutes.
The entire test takes between an hour to an hour and a half. Results are then generated in a report format and provided to the health care provider who ordered your study.
Complex Regional Pain Syndrome
For this pain disorder, we assess skin temperatures on the affected and contralateral (opposite) arm or leg by infrared thermography. We also assess the resting sweat levels on those limbs. Last, we perform QSART to measure stimulated sweat output in the affected and nonaffected limb. With CRPS, there is an asymmetry in stimulated sweat output between an affected and unaffected limb. The testing is not very useful if symptoms are present in both arms or both legs. We do not perform testing for pain in the face or trunk.
Reasons to Undergo Autonomic Reflex Screen
Reasons to undergo testing can range from concerns about having a small fiber neuropathy, orthostatic hypotension or orthostatic intolerance, postural orthostatic tachycardia syndrome, overt syncope, changes to sweating function, concern for degenerative disorders which can affect the autonomic nervous system etc.
For probable cardiac disorders, patients should be seen by a cardiologist and have tilt-table testing done in Cardiology for safety.
Schedule testing
To arrange for testing a prescription (order) should be obtained from your health care provider and can be sent electronically to our lab or faxed to (412) 647-5162.
The lab can be contacted by phone at (412) 647-5424.
Preparation for Testing
Once your testing is scheduled you will be contacted and provided with some written instructions regarding your testing.
Medications can affect the results of the test thus for a certain amount of time, usually 48 hours, and possibly longer, you may need to hold (stop) taking certain medications. We do recommend reaching out to your health care provider to ensure it is safe to stop taking medications and for how long.
During the 24 hours prior to your test do not drink any alcohol and do not perform any vigorous exercise or activity.
During the 8 hours prior to your test do not consume any caffeine (food or beverage) or smoke/use any tobacco/nicotine containing products.
During the 3 hours prior to your test do not consume a heavy meal, you can drink liquids and eat a light meal up to 2 hours before your test.
During your test do not wear tight stockings or an abdominal binder
Tilt testing cannot be performed on patients greater than 300 pounds. Notify the technicians if you have a history of retinal detachment as this may limiting testing, and you should ask your ophthalmologist if the Valsalva testing can be done.