Quantitative thermal perception testing in adults

In 225 adults aged 18 to 80 years, normative warm and cold perception thresholds were assessed at the volar distal forearm, thenar eminence, lower medial calf, and lateral dorsal foot using the method of limits and a Thermotest (Somedic, Stockholm, Sweden). A 1.5-cm x 2.5-cm thermode, a 1°C/s stimulus change rate, and a 32°C baseline temperature were applied. Thresholds of five consecutive stimuli were averaged. At the thenar eminence a 3°C/s stimulation was applied in addition to the 1°C/s stimulation. Effects of spatial summation were studied at the calf and forearm by additional testing with a 2.5-cm x 5.0-cm thermode. To evaluate the influence of skin temperature, thresholds were correlated with the pretest skin temperature at the tested sites. Reproducibility of stimulus perception was determined by comparing the lowest to the highest response to five consecutive stimuli. Results showed sufficient accuracy of thermal perception thresholds. Thresholds were higher with the 3°C/s stimulation than with the 1°C/s stimulation. Thresholds were lower with the large than with the small probe. Skin temperature had only minimal influence on thresholds. The use of a 32°C baseline temperature and a 1°C/s stimulus change rate is recommended. The large probe should be used at body sites where the entire thermode surface adjusts planely to the skin. Warming up the tested skin area is not necessary before thermotesting.