Compensatory contribution of the contralateral pyramidal tract after stroke.

Stroke is a leading cause of long-term disability with early accelerated followed by gradual recovery during the first 6 months after the ictus. The most important mechanism concerning early recovery is thought to be brain plasticity provided by anatomical and functional reorganization of the central nervous system after injury. Recent advances in noninvasive, functional brain imaging techniques provided some insight indicating the contribution of ipsilateral uncrossed corticospinal tracts in motor recovery after stroke. Since motor tracts vary considerably among subjects, the ratio of contralateral corticospinal tract fibers and their interhemispheric control versus the amount and function of ipsilateral corticospinal tract fibers may affect the scale of motor recovery after stroke. Further studies are needed to clarify the mechanisms of motor recovery after stroke in humans.