Minimum temperature felt as hot (MTH)--a new concept for grading the loss of temperature sensation in leprosy patients.

In order to grade the loss of the temperature sensation in the skin of leprosy patients, a newly designed instrument called the Temperature-Sensation-Testing-and-Grading device has been employed to determine the minimum temperature felt as hot (MTH) at the skin area. The MTH in normal subjects was observed to vary from one region of the body to another; it was generally higher on the distal parts of the extremities compared to the proximal parts; and it was also higher on the lower extremities compared to the upper ones. The abdomen and the back generally had the lowest values. There were no variations according to age (11-80 years) or sex and no differences on symmetrical sites of the body. The MTH value, however, showed a dependence on the environmental temperature, the values being lower at low environmental temperatures and higher at high environmental temperatures. But at the same site and the same environmental temperature, the MTH value was found to be almost constant. Different individuals had different MTH values at the same body site and even at the same environmental temperature. The unaffected skin of leprosy patients showed values comparable to the controls. At the leprosy lesions, however, the degree of sensory loss could easily be determined in comparison with the MTH at the contralateral/adjoining unaffected skin. Out of 54 leprosy patients, 7 patients had no sensory loss; in 27 patients the loss varied between 1 degree C and 20 degrees C; while in 20 patients the loss was complete--they could not perceive even 50 degrees C as hot.(ABSTRACT TRUNCATED AT 250 WORDS)