What is the role of motor evoked potentials (MEPs) for stroke motor recovery prognosis?

Updated: Aug 20, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

The recovery of motor function after a stroke varies. In the first days, the motor prognosis is difficult to establish from clinical and even head CT scan data.

The clinical application of MEPs in stroke is done mainly to evaluate the prognosis for recovery. (MEPs have a better predictive value for functional prognosis than do SEPs.) Most studies suggest that the early presence of MEPs after a stroke indicates a good recovery of daily functions. Absence of MEPs is associated with variable outcomes, usually poor. For patients who do not respond to cortical stimulation at stroke onset, the risk of poor functional recovery at 12 months is high and the probability of stroke-related death during this period is greater than for patients who do respond.

Takarada et al tested the hypothesis that transient vascular occlusion increases the excitability of the primary motor cortex during force exertion. The MEP amplitudes were enhanced with occlusion under all conditions, with the exception of 60% contraction. In contrast, no significant difference was observed between the MEP amplitudes obtained from the occluded or nonoccluded, relaxed flexor carpi ulnaris muscle. These results suggest that transient vascular occlusion increases the excitability of the motor cortex only during force exertion. [15]

Prolonged CMCT is found mainly in subcortical lesions. Severe cortical strokes are more likely to result in absent MEPs.

Reliability of intrasession MEP size is excellent in the lower limb of patients with stroke using as few as 6 MEPs, but intersession reliability is poor. Comparing MEP size measures across 2 or more sessions is questionable in the lower limb of patients with stroke. [16]

Transcranial magnetic stimulation-evoked neurophysiological parameters are useful measures for monitoring post-stroke patients. [17, 18]


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