Treatment-Induced Cortical Reorganization After Stroke in Humans

TLDR

Injury‑induced cortical reorganization is well documented, yet little is known about treatment‑induced plastic changes in the human brain. This study aimed to assess motor‑cortex reorganization induced by an effective rehabilitation treatment in stroke patients. Thirteen chronic stroke patients underwent focal transcranial magnetic stimulation mapping of hand‑muscle motor output before and after a 12‑day constraint‑induced movement therapy. Post‑therapy, the affected hemisphere’s hand‑muscle representation expanded, motor performance improved, adjacent areas were recruited, and six‑month follow‑up showed sustained function with cortical areas equalizing, demonstrating long‑term therapy‑induced brain plasticity.

Abstract

Background and Purpose —Injury-induced cortical reorganization is a widely recognized phenomenon. In contrast, there is almost no information on treatment-induced plastic changes in the human brain. The aim of the present study was to evaluate reorganization in the motor cortex of stroke patients that was induced with an efficacious rehabilitation treatment. Methods —We used focal transcranial magnetic stimulation to map the cortical motor output area 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 constraint-induced movement therapy. Results —Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After treatment, the muscle output area size in the affected hemisphere was significantly enlarged, corresponding to a greatly improved motor performance of the paretic limb. Shifts of the center of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas. In follow-up examinations up to 6 months after treatment, motor performance remained at a high level, whereas the cortical area sizes in the 2 hemispheres became almost 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 alteration in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury.