Thermoregulatory Sweat Test (TST)

A thermoregulatory sweat test (TST) measures your ability to sweat in a special chamber/lab/room that has controlled temperature, humidity and airflow regulation.

Why Would You Get a TST

The TST is helpful in identifying autonomic involvement in many neurologic disorders, including:

• Primary autonomic failure
• Secondary autonomic failure due to neuropathy (diabetes, primary systemic amyloid, lepromatous, idiopathic small fiber, and paraneoplastic)
• Myelopathy (syrinx, spinal cord injury, and multiple sclerosis)
• Surgical sympathectomy
• Disorders of sweat glands and skin. 

A TST can help monitor disease progression and recovery. 

Autonomic Conditions

The autonomic nervous system (ANS) controls many automatic functions in our bodies that we don't think about, helping keep everything balanced and working properly. This system is essential for survival and helps us deal with different situations in our environment. Dysautonomia is a disorder that affects how the ANS works. 

Symptoms Indicating a TST

• Inability to sweat properly, leading to heat intolerance
• Loss of bladder control, leading to infection or incontinence
• Dizziness, lightheadedness or fainting because of a loss of control over blood pressure
• Diarrhea, constipation or incontinence related to nerve damage in the intestines or digestive tract 
• Difficulty eating or swallowing 
• Life-threatening symptoms, such as difficulty breathing or irregular heartbeat

How a TST Works

If you sweat abnormally, a TST, along with other tests, can identify whether the dysfunction is in your peripheral or central nervous system and how severe it is. This test will help your doctor make a diagnosis and determine treatment options.

The TST is designed like a sauna. Heat and humidity are controlled in the room to help you produce sweat in all skin regions that are capable of sweating. You must reach a fever temperature.

A video camera allows your technologist and physician to monitor you continuously. A picture will be taken at the end of the test that the physician will analyze to see how your autonomic system reacted to the room's condition.

What to Expect and How to Prepare

You will have access to a shower and changing room for testing. We provide swimwear to wear during the testing, but you can bring your own — please be aware that your items could be permanently stained by the dye we use. 

The patient should have a light meal and be hydrated for the test. We will provide water, juice and a light snack if needed. Follow all medication instructions from your ordering physician. No over-the-counter allergy medications should be taken. A medication list will be mailed to and placed in you MyChart that explains what not to take and for how long.

The test can last up to an hour. The test can be uncomfortable.

After the test, it is important to rehydrate and get some rest.

Getting Your Results

Your doctor will provide your results in seven to 10 business days and will be given by the ordering provider.