cqvip:Objective: To evaluate motor cortex excitability changes by transcranial magnetic stimulation (TMS) following repetitive muscle contractionsE in patients with multiple sclerosis (MS); to state whether a typical pattern of post exercise motor evoked potentials (MEPs) is related to clinical fatigue in MS.Methods: In 41 patients with definite MS (32 with fatigue and 9 without fatigue according to Fatigue Severity Scale) and 13 controls, MEPs were recorded at rest: at baseline condition, following repetitive contractions until fatigue, and after fatigue, to evaluate post exerciseMEP facilitation (PEF) and depression (PED). Results: After exercise,MEP amplitude significantly increased both in patients and controls (PEF). When fatigue set in, MEP amplitude was significantly reduced in normal subjects (PED), but not in patients. Post exercise MEP findings were similar both in patients with and without fatigue. Conclusions: Our findings suggest an intracortical motor dysfunction following a voluntary contraction in MS patients, possibly due to failure of depression of facilitatory cortical circuits, or alternatively of inhibitory mechanisms.
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