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Therapy Can Alter Post-stroke Brain Function

Thirteen stroke survivors are the first humans to illustrate a dramatic new finding: after neurological injury, the human brain-just as the animal brain-can be helped by therapy to rewire itself, allowing for regained use of a previously unused limb.

Until now, there has been little information on treatment-induced plastic changes in the human brain, although injury-induced cortical reorganization is widely recognized. This study aimed to evaluate reorganization induced in the motor cortex of stroke patients via rehabilitation treatment.

Researchers used focal transcranial magnetic stimulation to map the cortical motor output area of a hand muscle in both sides in the 13 patients, all in the chronic stage of their illness. They were examined before and after a 12-day period of constraint-induced movement therapy, i.e. restraint of the less affected limb and rehabilitation treatment of the affected limb during most waking hours.

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 affected limb.

Shifts of the centre of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas, the study notes.

In follow-up examinations up to six months after treatment, patients' motor performance remained at a high level, and the cortical area sizes in the two hemispheres became almost identical. This represented a return of the balance of excitability between the two hemispheres toward a normal condition, the researchers suggest.

This is the first demonstration in humans of a long-term alteration in brain function linked to therapy-induced improvement in the rehabilitation of movement after neurological injury.
Stroke. 2000;31:1210.

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