The effect of induced hyperthermia on the blink reflex in multiple sclerosis.

In 76 patients with multiple sclerosis, the blink reflex was elicted electrically at normal body temperature and during induced hyperthermia to observe the effect on conduction within the reflex pathway through the brainstem. Special attention was directed to 31 patients with electrophysiologic evidence of reflex slowing, presumably because of demyelination in the reflex pathway. Hyperthermia did not induce any significant changes in mean reflex latency, amplitude, or duration in either the overall group of 76 or in the 31 patients with baseline blink reflex abnormalities. While the mean reflex latency did not change, 13 (33 percent) of 39 abnormal R1 responses from the 31 patients changed by 1.5 msec or more during hyperthermia, whereas change of similar magnitude was noted in only three (3 percent) of 90 normal R1 responses.