Thermal reflex sweating in normal and paraplegic man

¹ Department of Physiology, Stritch School of Medicine, and the Graduate School, Loyola University, Chicago, Illinois

Ten normal subjects and five patients with anatomically complete lesions of the spinal cord (T₃-T₈) were exposed to similar alterations in environmental temperature in a controlled climate chamber while sweating and temperature changes were recorded. In both groups, sweating was recruited in a similar pattern, starting first on the distal portions of the lower extremities and then successively on the thigh, trunk, upper extremities, and head. Sweating was far less intense on the paraplegic patient's lower extremity, but it illustrates positive sweating reflexes to thermal stimulation mediated by the "isolated" spinal cord. Sweating was dramatically inhibited when the subject was suddenly chilled by introducing relatively cool air (20–25 C) into the chamber. The normal subject reported a sensation of cooling, and sweating decreased before there occurred any detectable alteration in oral or rectal temperatures. Although multiple recordings of skin temperature were made, they were found to be quite unreliable at high environmental temperatures and cannot be considered reliable indexes of the presence or absence of relatively minute sweating responses. The functional participation of cutaneous thermoreceptors and the spinal cord in the mediation of thermal reflex sweating appears a certainty, but the low intensity of such sweating suggests that higher central nervous (hypothalamic) facilitation is essential for normal intensity.