Effects of a mirror-induced visual illusion on a reaching task in stroke patients: implications for mirror therapy training

Abstract

Background: Although most mirror therapy studies have shown improved motor performance in stroke patients, the optimal mirror training protocol still remains unclear.

Objective: To study the relative contribution of a mirror in training a reaching task and of unilateral and bimanual training with a mirror.

Methods: A total of 93 stroke patients at least 6 months poststroke were instructed to perform a reaching task as fast and as fluently as possible. They performed 70 practice trials after being randomly allocated to 1 of 5 experimental groups: training with (1) the paretic arm with direct view (Paretic-No Mirror), (2) the nonparetic arm with direct view (Nonparetic-No Mirror), (3) the nonparetic arm with mirror reflection (Nonparetic Mirror), (4) both sides and with a nontransparent screen preventing visual control of paretic side (Bilateral-Screen), and (5) both sides with mirror reflection of the nonparetic arm (Bilateral-Mirror). As baseline and follow-up, patients performed 6 trials using only their paretic side. Primary outcome measure was the movement time.

Results: We found the largest intervention effect in the Paretic-No Mirror condition. However, the Nonparetic-Mirror condition was not significantly different from the Paretic-No Mirror condition, while the Unaffected-No Mirror condition had significantly less improvement than the Paretic-No Mirror condition. In addition, movement time improved significantly less in the bimanual conditions and there was no difference between both bimanual conditions or between both mirror conditions.

Conclusion: The present study confirms that using a mirror reflection can facilitate motor learning. In this task, bimanual movement using mirror training was less effective than unilateral training.

Keywords: physical therapy; recovery of function; rehabilitation; stroke; upper limbs.