A practical guide to the evaluation of the functional integrity of the corticospinal tract by transcranial magnetic stimulation in post-stroke patients

Abstract

INTRODUCTION: Transcranial magnetic stimulation (TMS) can be a particularly useful tool to assess the integrity of corticospinal tract (CST) in post-stroke patients, based on the motor evoked potential (MEP) of which we can determine the extent of brain damage and predict motor recovery after brain injuries. OBJECTIVE: To provide a practical guide to assess the functional integrity of the CST in the hand area of primary motor cortex (Hand-M1) using single-pulse TMS. RESULTS: A step by step procedure should be initiated with markings to find C3 or C4 from the 10-20 system, depending on which hemisphere is damaged, with the proper coil positioning at a 45° angle for we to properly find the MEP navigating from the original point. If no potentials are evoked at rest condition, MEP should be searched during a slight tonic contraction of the target muscle. If no voluntary movement can be produced in the affected muscles, facilitated MEPs should be searched with an isometric recruitment of the contralateral homologous target muscles. MEP will be considered absent if no visible muscle contraction is identified after the pulse. In addition, we can perform MEP search with electromyographic recordings for a peak-to-peak signal analysis. CONCLUSION: We can use this practical guide to assess the functional integrity of CST in Hand-M1 with single pulse TMS to consider a present or absent MEP and determine the extent of brain damage and predict a possible motor recovery after stroke.