Dynamic Sweat Test (DST) (Autonomic Unit)

Thermoregulation is an important mechanism that concerns the control and maintenance of the body’s core temperature. It is one of the many bodily processes controlled by the autonomic nervous system.

An example of this can be seen in our decision to add or remove items of clothing according to whether we are feeling too cold or hot.

When this process is impaired, the body struggles to perform processes that help to regulate the body’s core temperature, including the ability to sweat.

In the Autonomic Unit, one of our key focus areas is sweating abnormalities caused by autonomic dysfunction.

A DST is a clinical test that is used to aid diagnosis of disorders related to thermoregulation and sweat production abnormalities in the body. The test measures sweat production on the lower legs and forearms in a controlled environment to assist the consultant in diagnosing medical conditions or planning and carrying out treatments.

A DST is a useful diagnostic test, although any clinical benefit should always outweigh the possible risks associated with the procedure.

A common concern from patients is whether the five-minute stimulation hurts. The feeling is generally described as itchy/tingly but not painful. If you do find it too painful, please inform the clinical autonomic scientist (CAS) performing your test. You may have small red patches on your skin following the procedure. These areas should not hurt and will fade over the following 48 hours.

The test requires the use of small amounts of Iodine and Pilocarpine applied to the skin. If you are allergic to either of these substances or notice signs of an allergic reaction during testing, please inform the CAS performing your test.

The decision to have a DST is entirely yours. Declining this procedure will not affect our attitude towards you or influence any other aspect of your care. It may mean, however, that your consultant cannot be as certain or specific about any future treatment or diagnosis.

Your consultant or clinical nurse specialist (CNS) will have considered the potential risks and benefits of having a DST during your initial referral. There may be some alternative methods available under certain circumstances, although the possibility of these should be discussed with your referring doctor or CNS.

You may need to stop certain medications prior to testing, although the consultant or CNS should be able to advise you during your initial consultation; if you are unsure, please call us directly or ask us when you confirm your appointment.

Please do not eat four hours prior to testing; you may drink water only.

If you are not able to lie still on your back for prolonged periods,
please inform us by telephone.

Please avoid caffeine (such as tea or coffee) and do not smoke (including e-cigarettes) four hours prior to testing.

Please do not apply body creams or lotions on the day of testing and please remove any fake tan.

Please drink at least 500ml water in the four hours before testing to ensure adequate hydration.

We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent. This confirms that you agree to have the procedure and understand what it involves.

If you are unsure about any aspect of your proposed treatment, please do not hesitate to speak with a senior member of staff again.

The testing procedure

You will be asked to lie down on your back while the CAS performing your test assesses the sweat production in your lower legs and forearms.

A weak electrical current consisting of two electrodes is passed onto a small area of your skin for five minutes to stimulate sweating. This is tingly/itchy but not painful. One electrode uses a small piece of sponge soaked in saline while another electrode uses a small piece of sponge soaked in Pilocarpine. This aids the stimulation of the sweat glands.

Iodine is then applied to each stimulated area of the skin and the sweating in each limb is measured by pressing starch paper against your arm or leg. A video camera will be used to record the sweating produced over three minutes. This test lasts approximately one hour.

Once you have completed all your clinical tests with us, the results will be analysed and discussed at a multi-disciplinary team (MDT) meeting.

A brief summary letter will then be sent to you and your referring doctor (normally your GP) detailing the results of your tests.

You will then be contacted by one of our consultants or CNS for a follow-up appointment to explain the results in more detail, and to also answer any questions you may have.

Once you have completed all your clinical tests with us, the results will be analysed and discussed at a multi-disciplinary team (MDT) meeting.

A brief summary letter will then be sent to you and your referring doctor (normally your GP) detailing the results of your tests.

You will then be contacted by one of our consultants or CNS for a follow-up appointment to explain the results in more detail, and to also answer any questions you may have.

You may find the following website useful: 

www.uclh.nhs.uk/nhnn

UCLH cannot accept responsibility for information provided by other organisations.

Address:

National Hospital of Neurology and Neurosurgery

The Autonomic Unit

2nd Floor Queen Mary Wing

Queen Square

London

WC1N 3BG

Direct tel: 0203 448 3079

Switchboard: 0203 456 7890

Fax: 0203 448 3878

Email: uclh.enquiry.autonomic.secretaries@nhs.net

Website: www.uclh.nhs.uk/nhnn

The Autonomic Unit is located on the second floor of the Queen Mary Wing at the National Hospital for Neurology & Neurosurgery, Queen Square.

Please follow signs from the main entrance towards the Queen Mary Wing and you should find the appropriate set of lifts/stairs on your right-hand side. Head to the second floor and use the intercom to contact our admin team who will let you in once you have confirmed your identity.