An instrument for measurement of thermal thresholds in man

Routine clinical electrophysiological techniques assess function in the large diameter, motor and sensory nerve fibres, but not in the smaller diameter fibres subserving pain, thermal sensation and autonomic function. The instrument we describe measures thermal sensation thresholds to both cooling and warming thus providing an index of function in the small diameter thinly myelinated A delta fibres and unmyelinated C fibers respectively. A commercial version, the Thermal Threshold Tester (TRIPLET) provides a portable instrument for routine clinical use. It has a particularly important role in the sequential and quantitative monitoring of small nerve fibre function as for example in diabetic neuropathy. It can also be applied to the study of small nerve fibre function in persons exposed to potentially neurotoxic substances either as medication or in industry.