Thermal testing Q&A
Q: What is thermal testing?
A: Thermal Testing procedure is similar to that employed in such routine tests as eye and hearing examinations, where patients are asked to respond to visual or auditory stimuli. Thermal testing is performed by applying the a thermode (thermal probe) on the patient’s skin to heat or cool the skin. Patients respond to the temperature stimuli by pushing a button, and the sensory thermal threshold is recorded and automatically compared to an age-matched normative data.
Q: What would the thermal testing results show?
A: When thermal testing shows a deviation from the normal range, the indication can be an existence of peripheral nerve disease or damage due to injury, illness or toxic exposure. Thermal testing comparing contra-lateral body sites and longitudinal (or serial) evaluation before and after therapy, can also be routinely employed.
Q: What are the available modalities?
A: Thermal testing of the sensory nerve system measure the thresholds for 4 sensory sub-modalities:
Warm sensation (WS), for normal subjects, usually at 1- 2ºC above adaptation temperature (C fiber mediated sensation)
Cold sensation (CS), for normal subjects, usually at 1- 2ºC below adaptation temperature (A-delta fibers mediated sensation
Heat-induced pain (HP), threshold around 45ºC (mostly C fiber mediated sensation, with some involvement of A-delta fibers)
Cold-induced pain (CP), the most variable and difficult to assess of all previous modalities, at about 10º C (combination of both C and A-delta fiber mediated sensation)