Spinal mediation of thermally induced sweating.

The sweat responses of nine patients with physiologically complete lesions of the spinal cord (six cervical and three thoracic) were recorded by two different techniques while the patients were exposed to elevated environmental temperatures. Oral temperatures, heart rate and respiration were monitored throughout the observational periods. Oral temperature invariably rose during exposure to heat and both heart rate and respiration tended to increase. Sweating was detected on all of the test areas by both the iodine-starch-paper technique and the quinizarin technique, but it was of widely varying intensity in different portions of the body. In the patients with cervical lesions sweating was generally profuse on the head and neck and occurred in progressively decreasing intensity down to the level of the umbilicus. It was invariably present, but only in very low intensity, on the lower extremity. Sweating was frequently present as a result of manipulation of the patient during the initial preparations, but this generally declined or stopped before the heat was turned on. With application of heat, sweating was recruited on previously dry areas or increased in intensity on those areas in which it was previously present. After oral temperature had increased moderately, the heat was turned off and the doors of the chamber opened widely so that the heat stimulus was suddenly removed. Despite a continued rise in oral temperature, sweating stopped or decreased dramatically. These results are interpreted to indicate the direct mediation by the isolated spinal cord of reflex sweating responses to a heat stimulus applied to the skin. The general distribution of sweating was similar to that associated with distension of the urinary bladder, and careful attention was taken to avoid this complication. The distribution of sweating on the patients with lesions in the thoracic cord was quite different, being most obvious and profuse on the lower extremities and lower trunk and completely absent from the upper trunk, head and upper extremities.