Using surface electromyography to guide the activation during motor-evoked potential measurement: An activation control method for follow-up studies

Objective: This study evaluated the reliability and validity of a convenient method that uses the real-time feedback surface electromyography (sEMG) to control muscle activation while measuring the MEP recorded from the quadriceps muscle in patients with stroke.Methods: It measured the MEP parameters as well as the clinical assessment at initial test. Participants were directed to adjust their quadriceps contraction to extend the knee isometrically and maintain the EMG amplitude at 0.2 mV. MEPs were measured 2 weeks after the initial test again to assess the reliability of this measurement.Results: A good test-re-test reliability was demonstrated with an intra-class correlation coefficient (ICC) > 0.8 for the motor threshold and a moderate reliability (ICC > 0.6) for the MEP latency and MEP amplitude, for both paretic and non-paretic legs. Patients with present MEPs had significantly higher scores in muscle power, the Fugl-Meyer assessment, the balance sub-scale of performance-oriented mobility assessment and the Barthel index; and lower NIHSS scores than those of patients with absent MEPs (all p <0.05).Conclusion: The sEMG-guided low level muscle activation is suitable for MEP assessment in patients with leg weakness after a stroke and may be used for long-term follow-up studies.