EFFECTS OF INDUCED HYPERTHERMIA IN MULTIPLE SCLEROSIS: DIFFERENCES IN VISUAL ACUITY DURING HEATING AND RECOVERY PHASES

Visual acuity in five multiple sclerosis (MS) patients was quantitatively monitored during the induction of hyperthermia and the subsequent spontaneous return of body temperature to base line (“cooling”). During heating acuity decreased monotonically. During “cooling” acuity was restored but, in three of the five patients, along a different temperature-acuity trajectory; that is, acuity at any temperature during “cooling” tended to be better than acuity at the same temperature reached during heating. In two patients acuity upon return to base-line temperature was significantly better than it had been before the induction of hyperthermia; in one case the difference was striking and significant at the .001 level. The difference in the second case was smaller but also significant (p < 0.02). The significance of these findings in helping to better understand the physiologic basis of temperature effects in MS is discussed.