Mapping clinically relevant plasticity after stroke

After stroke, patients show a wide range in the degree of recovery. Recovery occurs on the basis of discrete physiologic events. Identifying and measuring these events will be useful for a better understanding of stroke recovery mechanisms. The most extensive experience mapping these events has been with positron emission tomography, functional magnetic resonance imaging, and transcranial magnetic stimulation. This article reviews brain mapping studies that have examined stroke recovery. Serial assessment of patients during recovery raises the need for control studies evaluating the effect of intra-subject variability over time. The clearest insights into the significance of bilateral activation during unilateral movements by the stroke-affected hand will come from studies that include bilateral electromyographic measurements. Most brain imaging studies have focused on patients with very good recovery; further study of patients with a wide range of outcomes is needed. The described brain mapping methods have complementary strengths. Insights into the biological basis of recovery may best be achieved when results are considered together. With the advent of treatments targeting stroke recovery, measurement of post-stroke restorative events may also have value as a surrogate end point in clinical trials.