Circadian and hypothermia-induced effects on visual and auditory evoked potentials in multiple sclerosis

Objectives: Body cooling has been proposed as a symptomatic treatment for m ultiple sclerosis. This study aimed to assess the effects of body cooling a nd of circadian variations on clinical parameters and on visual and auditor y evoked potential measures in multiple sclerosis patients. Methods: Clinical status was assessed and VEPs, BAEPs and MLAEPs tall with two stimulus frequencies) were recorded a total of 4 times on two separate days (two times per day at 08:30 and 15:00 h each day) in 10 multiple scler osis patients and 10 controls. On one of these days, the subjects were subm itted to body cooling before the afternoon session. Results: Tympanic temperature was significantly higher in the afternoon. Co oling lowered the temperature by 1.4 degrees C. No clinical effects were ob served. Circadian effects were detected on VEP amplitude, which increased b oth in controls and in patients at low stimulus frequency (P < 0.01), and i ncreased in controls and decreased in patients at high stimulus frequency ( interaction: P < 0.01). Cooling determined an increase in BAEP I-V peak-to- peak time in controls, and a reduction in patients at high stimulus frequen cy (interaction: P < 0.01). In patients, cooling also determined a great in crease in MLAEP amplitude (interaction: P < 0.001). We did not find cooling effects on VEP measures. Conclusions: Visual and auditory evoked potentials showed differences in ci rcadian and cooling effects between controls and multiple sclerosis patient s. These differences are consistent with the hypothesis of temperature-depe ndent conduction blocks in demyelinated fibers. Cooling may have a clinical effect in selected patients only. (C) 2000 Elsevier Science Ireland Ltd. A ll rights reserved.