Treatment-induced cortical reorganization after stroke in humans

Background and Purpose-Injury-induced cortical reorganization is a widely r ecognized phenomenon. in contrast, there is almost no information on treatm ent-induced plastic changes in the human brain, The aim of the present stud y was to evaluate reorganization in the motor cortex of stroke patients tha t was induced with an efficacious rehabilitation treatment. Methods-We used focal transcranial magnetic stimulation to map the cortical motor output ores of a hand muscle on both sides in 13 stroke patients in the chronic stage of their illness before and after a 12-day-period of cons traint-induced movement therapy. Results-Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After tr eatment, the muscle output area size in the affected hemisphere was signifi cantly enlarged, corresponding to a greatly improved motor performance of t he paretic limb, Shifts of the center of the output map in the affected hem isphere suggested the recruitment of adjacent brain areas. In follow-up exa minations up to 6 months after treatment, motor performance remained at a h igh level, whereas the cortical area sizes in the 2 hemispheres became almo st identical, representing a return of the balance of excitability between the 2 hemispheres toward a normal condition. Conclusions-This is the first demonstration in humans of a long-term altera tion in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury.