عملکرد حرکتی داوطلبانه در بیماران مبتلا به سندرم خستگی مزمن

Introduction: The pathogenesis of chronic fatigue syndrome (CFS) remains unknown. In particular, little is known of the involvement of the motor cortex and corticospinal system. Methods: Transcranial magnetic stimulation (TMS) was used to assess corticospinal function in terms of latency and threshold of motor-evoked potentials (MEPs) in thenar muscles. Reaction times and speed of movement were assessed using button presses in response to auditory tones. Results: Patients had higher (P<.05) self-assessed indices of fatigue (7/10) than for pain (5/10), anxiety (4/10) or depression (3/10). Mean (±S.E.M.) simple reaction times (SRTs) were longer (P<.05) in the patients (275±19 ms) than in the controls (219±9 ms); choice reaction times (CRTs) were not significantly longer in the patients. Movement times, once a reaction task had been initiated, were longer (P<.05) in the patients in both SRTs (patients, 248±13 ms; controls, 174±9 ms) and CRTs (patients, 269±13 ms; controls, 206±12 ms). There was no difference (P>.05) in threshold or latency of MEPs in hand muscles between the patients (threshold, 54.5±2.2% maximum stimulator output [% MSO]; latency 22±0.3 ms) and controls (threshold 54.6±3.6% MSO; latency 22.9±0.5 ms). Regression analysis showed no correlation (P>.05) of SRTs with either threshold for MEPs or fatigue index. Conclusion: Corticospinal conduction times and excitability were within the normal range despite a slower performance time for motor tasks and an increased feeling of fatigue. This suggests that the feeling of fatigue and the slowness of movement seen in CFS are manifest outside the corticospinal system.

Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), is characterized by the feeling of fatigue, musculoskeletal pain and many neuropsychiatric symptoms [1]. The pathogenesis of CFS remains unknown, although it does appear to be associated with neuroendocrine [2] and immunological abnormalities [3]. A number of studies have measured reaction times in CFS and have reported them to be slowed [4], [5], [6] and [7]; however, they have not all differentiated between choice and simple reaction time (SRT) paradigms. One previous study that investigated corticospinal function in CFS showed increased facilitation of motor-evoked potential (MEP) to transcranial magnetic stimulation (TMS) of the motor cortex [8] after exercise. Others have shown that the excitability of the motor cortex is unstable in CFS during sustained muscle activity [9] and speculated that this might exaggerate the perception of fatigue. In the present study, our hypothesis was that altered corticospinal function might, at least in part, be responsible for the genesis of fatigue. To test this, we have measured simple and choice reaction times (CRTs), electrophysiological indices of corticospinal function and self-assessment ratings of symptoms.