Evidence for a central mechanism in the process of fatigue in people with multiple sclerosis

Abstract

The study aimed to establish quantitative and qualitative aspects of fatigue among a group of people with multiple sclerosis (MS) who had identified fatigue as a troublesome symptom and a control group of healthy adults. An interview, a fatigue diary and a fatigue-inducing experiment were designed and the Nottingham Health Profile was employed. People with MS experienced significantly more fatigue than healthy adults, on a daily basis. Factors noted to cause and to relieve fatigue were similar in people with MS and healthy adults. The only differences were that a hot bath improved fatigue in healthy adults and accentuated it in people with MS and that more of the healthy adults mentioned lack of sleep as a cause of fatigue. Physiological muscular fatigue during a quadriceps test was of similar magnitude in the two studied groups but the perceived fatigue levels were disproportionally high in the patient group. The results support the view that central mechanisms are responsible both for muscle weakness and for the sense of fatigue experienced so frequently in multiple sclerosis. This central mechanism is likely to reside in motor pathways within the nervous system. Further studies, measuring corticomotor conduction times, motor unit firing frequencies and metabolic factors, are recommended.