Fatigued patients with multiple sclerosis have impaired central muscle activation.
BACKGROUND
The pathogenesis of fatigue in multiple sclerosis (MS) is poorly understood.


OBJECTIVE
To elucidate the role of central motor activation we hypothesized that patients with primary fatigue have impaired central motor function and increased fatigability as compared to secondary fatigued and non-fatigued patients.


METHODS
Sixty patients with relapsing remitting MS and an Expanded Disability Status Scale score <or= 3.5 were recruited and grouped as fatigued (Fatigue Severity Scale (FSS) >or= 5.0) or non-fatigued (FSS <or= 4.0). Nineteen patients were primary fatigued, 20 secondary fatigued and 21 non-fatigued. Maximal voluntary contraction, central activation and peripheral activation were determined by percutaneous twitch interpolation of the right quadriceps muscle.


RESULTS
Maximal voluntary contraction was similar between groups but did relate to scores of fatigue. Peripheral activation was similar in all groups. Central activation was impaired in both groups of fatigued patients compared to non-fatigued patients being 0.96(0.05) in primary fatigued and 0.96(0.04) in secondary fatigued versus 0.99(0.1) in non-fatigued patients. The impairment of central motor activation was related to degree of fatigue in all patients. During fatiguing exercise there was a similar loss of strength, without any time differences between the three groups.


CONCLUSIONS
We conclude that impaired central motor activation is involved in MS-fatigue.
Andreasen
A K
AK
Department of Neurology, Aarhus University Hospital, Denmark. ak@ki.au.dk
Jakobsen
J
J
Petersen
T
T
Andersen
H
H
D000328:Adult; D002490:Central Nervous System / Q000503:physiopathology*; D004185:Disability Evaluation; D004558:Electric Stimulation; D005221:Fatigue / Q000209:etiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000150:complications / Q000503:physiopathology*; D018763:Muscle Fatigue; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D009483:Neuropsychological Tests; D052097:Quadriceps Muscle / Q000294:innervation*; D012720:Severity of Illness Index; D014836:Volition; D055815:Young Adult