Comparison of TMS-induced arm activation and upper limb functional tests in hemiparetic stroke

Stroke has a major impact in the total cost of healthcare in the Western world as stroke is the most common cause of long-term disability [1]. In attempts to enhance motor recovery after stroke effective treatment strategies have been developed in recent years. Appropriate evaluation of the intervention programs requires comprehensive and accurate assessment of the residual abnormal function. In the present study we compare two well-known clinical functional scoring tests developed for the assessment of hemiparetic upper limb function due to stroke and navigated transcranial magnetic stimulation (nTMS), which measures involuntary target muscle response to cortical stimulation. The aim is to investigate the equivalence of these methods and thus add objective evidence of the limb function to strengthen evidence-based practice. In addition to functional tests, four muscles of both arms were studied in twenty chronic stroke patients. Those patients without motor evoked potentials (MEP) to nTMS in the affected upper limb had significantly lower total score in Action Research Arm Test and Wolf Motor Function Test and longer performance time than those patients with MEP. Patients, in whom MEP in each of the four target muscles was elicitable, had better than average scores in clinical functional tests while patients, in whom no MEP was elicitable in any target muscle, had worse than average scores. Transcranial magnetic stimulation adds crucial information when clinical assessment based on voluntary activation by command is challenging, e.g. in patients suffering from cognitive deficits.