No effect of cooling on cognitive fatigue, vigilance and autonomic functioning in multiple sclerosis

Abstract

Background: Fatigue is a common symptom in Multiple Sclerosis (MS) and body cooling may be an important non-pharmacological treatment strategy for fatigue by, for instance, reducing the loss of axonal conduction efficiency due to Uhthoff’s phenomenon. However, up to now, no studies have demonstrated such a treatment effect for mentally induced fatigue. Methods: In this single-blinded randomized placebo controlled cross-over design we studied the effects of cooling on cognitive fatigue and autonomic functioning (heart rate variability and sympathovagal balance measures) during a vigilance task in 31 MS patients and 10 controls. Results: Task performance, fatigue and sympathovagal balance did not differ between verum- and placebo condition after controlling for depressive mood. MS patients showed more omissions on the vigilance test than controls; their performance declined during the task and this correlated significantly with cognitive fatigue. Cardiac sympathetic drive remained unchanged during vigilance testing in MS patients, but it increased significantly in controls. Conclusion: Cooling has no impact on experienced cognitive fatigue and on cognitive performance in MS patients. Vigilance testing seems to be an appropriate behavioural measure of cognitive fatigue. Cardiac sympathetic drive to compensate for mental strain is reduced in MS patients, indicating an autonomic dysfunction.