The effects of motor imagery training on upper-extremity functional reorganization in stroke patients: A fMRI study

Objective: To measure the efficacy of motor imagery training (MIT) in improving stroke patients' upper-extremity functional outcomes and to find the possible cortical reorganization patterns associated with the improvement of motor function with functional magnetic resonance imaging (fMRI) response during a passive hand task. Method: Nine stroke patients with stable, pure and motor deficits were enrolled. All patients received motor imagery training for 4 weeks (30 minutes a day, 5 days a week) and conventional rehabilitation therapy. Functional evaluation was assessed by the upper extremity of Fugl-Meyer assessment (FMA-UL) before treatment and 4 weeks after treatment. fMRI was also administered to assess cortical activation changes in regions of interest (ROIs) that included the primary and secondary motor and sensory areas while the patients executed a passive fist clutch task at the two time points before and after 4-week interventions. Result: After the interventions, FM-UL scores of the 9 stroke patients dramatically increased (22.44±11.59 vs 39.78±14.03, P=0.011). There were two types of cortical reorganization patterns existed in the patients. One pattern consisted of persistent growth in activation in contralateral sensorimotor cortex(cSMC) for most patients (6 patients), and the other pattern consisted of focusing of activation in cSMC with increasing of the laterality index of SMC (LI-SMC) for a small portion of patients (3 patients). Conclusion: This study indicated that, for the stroke patients with upper-extremity impairments, a 4-week regimen of motor imagery training resulted in functional improvement in upper-extremity. These interventions may elicit plastic changes; i.e., the possible two cortical reorganization patterns in the brain: increasing recruitment and focusing recruitment in cSMC. When the patients improved their functions, they mainly chose the cortical reorganization which was dominated by the activation in cSMC.