Analysis of recovery processes after stroke by means of transcranial magnetic stimulation

The objective of this study was to use motor evoked potentials (MEPs) to analyze the integrity of fast corticospinal functions as the neurophysiologic basis for motor recovery in stroke patients. This was a cohort study including 44 acute stroke patients with paralysis of the upper or the lower extremity. Motor evoked potentials of the abductor digiti minimi, the biceps brachii, the vastus medialis, and the tibialis anterior were performed within 10 days (mean, 6.9 days; range, 3 to 10 days) and 40 days (mean, 27.8 days; range, 14 to 40 days) after stroke onset. A separate score was defined for proximal and distal motor functions of the upper and lower extremity within the original Fugl-Meyer motor assessment. Motor performance was evaluated simultaneously with the MEP assessments and 26 weeks after stroke. For all the muscles in which a response was present during the first investigation, obvious recovery of the fast corticospinal functions occurred. For the abductor digiti minimi amplitude ratio and the vastus medialis MEP amplitude the differences between the two investigations were significant. An MEP response could be elicited in more cases at the second than on the first MEP assessment. A present MEP response during the first registration indicated nearly always subsequent motor recovery, both for proximal and distal motor functions of the upper and lower extremity. However, motor recovery was also observed in some patients for whom no MEP response could be elicited. Regression analysis showed significant relationships between the abductor digiti minimi (P = 0.020/0.004 [t1/t2])and biceps brachii (P = 0.020/0.004 [t1/t2]) MEP amplitude parameters and the 26-week hand and arm motor scores. No relationship existed between the tibialis anterior and the vastus medialis MEP parameters and the leg motor scores. Motor recovery manifests neurophysiologically often as the recovery of fast corticospinal functions. In many cases, assessment by MEPs is more sensitive than clinical examination to detect residual corticospinal functions, which forms the pathophysiologic basis for the predictive value of MEPs for motor recovery after stroke.