Increased postural sway in persons with multiple sclerosis during short-term exposure to warm ambient temperatures.

Background: Multiple sclerosis (MS) is a neurological disease marked by demyelination and axonal loss. Individuals with MS experience increases in clinical signs and symptoms during heat exposure.

Objective: To test the hypothesis that moderate heat exposure adversely affects postural sway in individuals with MS.

Methods: Ten individuals with relapsing-remitting MS (50±8y) and nine controls (47±10y) were examined under a Thermal and a Time Control trial. Following a 30min thermoneutral baseline (25°C, 30% relative humidity (RH)), stand tests randomized with eyes open and closed, were performed. For Thermal, subjects were first exposed to 60min of heating (40°C, 30%RH) followed by 60min of cooling (20°C, 30%RH). For Time Control, subjects remained in a thermoneutral environment throughout. Stand tests were repeated at consistent times in both trials.

Results: No difference in skin and core temperatures between groups were observed for any trial (P>0.05). During heating, postural sway was higher in MS relative to control subjects (eyes open, P=0.03; eyes closed, P=0.011). No differences in postural sway, regardless of eye status, were observed during the Time Control trial for either group (P>0.05).

Conclusion: These data demonstrate that exposure to a moderate heating environment increases postural sway in patients with MS.