Thermal sensitivity is not changed by acute pain or afferent stimulation.

The effect of conditioning stimulation on thermal sensitivity and clinical pain was studied in 40 patients and six healthy subjects. Thresholds regarding cold, warm and heat pain perception did not differ significantly between the painful and non-painful skin areas in patients or between patients and healthy subjects before stimulation. The patients received either 100 Hz TENS, 2 Hz TENS, 100 Hz vibration, or placebo. No significant changes in thermal sensitivity were observed during and after conditioning stimulation in any of the test groups, although 24/40 (60%) of the patients reported reduction of their clinical pain intensity. The results indicate that (a) thermal sensitivity is not influenced by the presence of clinical pain, (b) the effects of stimulation on thermal sensitivity (thresholds) and clinical pain are not closely related, (c) central inhibitory effects of TENS and vibration are crucial for their pain relieving capacity.