An improved automated method for the measurement of thermal thresholds. 1. Normal subjects.

Abstract

SUMMARY Clinical tests of thermal sensation are poorly quantified and not strictly modality specific. Previous automated thermal testing systems have had limited usefulness with high intraand inter-individual variability. This paper describes an automated thermal system (Glasgow system) which is an extensive modification of previous techniques to answer these criticisms. It comprises a microprocessor-driven Peltier element and utilises the forced choice method of psychophysical analysis to determine the thresholds to thermal stimulation. In a control group of 106 healthy subjects the mean heat threshold for the wrist was found to be 0 23°C (SD = 0.06°C) and the mean cold threshold 0 15°C (SD = 0.05°C). Repeated determinations showed a maximum of 5% intra-individual variation in comparison to previously reported values of up to 150%. through the element to maintain background skin temperature, allowing the heat pumping capacity of the thermode to be reserved exclusively for the test studies.6Simple measurements of thresholds were superseded by the "Marstock method" where the temperature interval between the perceptual thresholds for warm and cold stimuli was defined as the most sensitive index of neural abnormality.79 In this interval, the "warm-cold difference limen", no thermal sensation is appreciated. These short-term studies were repeated over periods of minutes but longer term studies repeated over days showed an unsatisfactory intra-individual variation of up to 150% between estimations.'0 This variability was attributed to central processing mechanisms although variation due to patient bias and reaction time had not been excluded.The most recent studies have used automated control systems to operate the Peltier element and

Hypoxia increases the cutaneous threshold for the sensation of cold

“…The difference may be due to either different methods by which thermosensitivity is assessed, various thermal sensitivity of skin areas, or both. Thermosensitivity has been often determined on other body sites (Jamal et al 1985;Meh and Denislic 1994), but data on thermal sensitivity of the toes is lacking. Regional differences in thermosensitivity (Nadel et al 1973;Crawshaw et al 1975;Tipton and Golden 1987;Burke and Mekjavic 1991) may also contribute to the observed difference in thresholds between studies.…”

Sensory neuropathies including painful and toxic neuropathies

“…Although the test results are reliable, the requirement of a specialized testing site and expertise may make the method less easily accessible in a clinical setting. Another quantitative method of testing for thermal cutaneous sensation is based on the measurement of temperature perception thresholds for warmth and cold using a thermode at the ventral side of the wrist [39].…”

Inert gas narcosis has no influence on thermo-tactile sensation

“…Whereas some studies have observed no signiWcant diVerence in the thermo-tactile sensation between male and female subjects (Gray et al 1982;Jamal et al 1985;Dyck et al 1987), others have reported that female subjects appeared to have lower thermo-tactile discrimination thresholds (Meh and Denislic 1994;Golja et al 2003), or have found lower warm thresholds and higher cold thresholds in females than in males (Kenshalo 1986;Doeland et al 1989;Lautenbacher and Strian 1991;Liou et al 1999;Seah and GriYn 2008). One possibility for the gender diVerence observed by some studies has been oVered by Gøransson et al (2004), who conWrmed on a sample of older and professionally more heterogeneous individuals than included in the present study, gender diVerences in the density of epidermal nerve Wbres in healthy people.…”

“…Based on these Wndings, we can assume that changes of local skin temperatures at the testing sites were due to the insulation provided by the thermode, preventing heat dissipation. Stevens and Choo (1998) showed that at all ages, some regions of the body are more sensitive to temperature than others, and in addition, that the human integument is uniformly more sensitive to cold than to warm as assessed by cutaneous thresholds (Jamal et al 1985;Fowler et al 1987;Doeland et al 1989). Our results do not conWrm this, because the overall median thresholds across subject and experimental conditions were the same (0.4°C) for cold and warm thresholds and for upper (i.e.…”