Understanding the pattern of functional recovery after stroke: facts and theories.

Longitudinal studies show that almost all stroke patients experience at least some predictable degree of functional recovery in the first six months post stroke. However, the non-linear pattern as a function of time is not well understood. Several mechanisms are presumed to be involved, such as recovery of penumbral tissues, neural plasticity, resolution of diaschisis and behavioural compensation strategies. Rehabilitation is believed to modulate this logistic pattern of recovery, probably by interacting with these underlying processes. However, prediction models that are adjusted for the effects of time after stroke onset suggest that outcome is largely defined within the first weeks post stroke, although functional improvement has been found to extend beyond six months post stroke. In addition, kinematic studies show that functional improvement is more than recovery from impairments alone, suggesting that patients are able to improve in terms of gait or dexterity deficits using behavioural compensation strategies. Therefore, understanding the impact of task-dependent cortical activation patterns in non-invasive methods requires not only information derived from longitudinal studies pertaining to functional outcomes, but also a better understanding of what is kinematically learned during the acquisition of new skills.