Fatigue in multiple sclerosis is associated with abnormal cortical activation to voluntary movement - EEG evidence

Converging evidence is consistent with the view that fatigue in Multiple Sc lerosis is independent from pyramidal tract involvement, suggesting a possi ble involvement of frontal areas. During voluntary movement, changes of the EEG rhythms can be observed over sensorimotor areas. Event-related desynch ronization (ERD) of the 10 and 20 Hz frequency bands occurs during motor pl anning and execution and is followed after movement termination by event-re lated synchronization (ERS), expressing cortical idling or inhibition. We e valuated the pattern of cortical activation to voluntary movement in MS pat ients complaining of fatigue assessed using the Fatigue Severity Scale. Fif teen MS patients complaining of fatigue, IS MS patients without fatigue, an d 14 normal controls were studied. The two patients groups were similar for age, sex, disease duration, and were not disabled (score <1.5 at the Expan ded Disability Status Scale). Twenty-nine channel EEG was recorded during a bout 60 self-paced extensions of the right thumb. The onset latency and amo unt of the contralateral sensorimotor (C3 electrode) 10 and 18-22 Hz ERD we re similar in the three groups. ERD was more widespread anteriorly in the f atigue group compared with normal controls (P < 0.01 over Fz electrode). Po stmovement contralateral sensorimotor 18-22 Hz ERS was significantly lower in fatigue MS patients compared with normal subjects (P < 0.005) and with n onfatigue MS patients (P = 0.02), These findings are consistent with a cent ral origin of fatigue in MS and indicate cortical dysfunction even during a simple motor task, resulting in hyperactivity during movement execution an d failure of the inhibitory mechanisms intervening after movement terminati on. (C) 2001 Academic Press.