How to perform mirror therapy after stroke? Evidence from a meta-analysis

Background: A recently updated Cochrane review for mirror therapy (MT) showed a high level of evidence in the treatment of hemiparesis after stroke. However, the therapeutic protocols used in the individual studies showed significant variability. Objective: A secondary meta-analysis was performed to detect which parameters of these protocols may influence the effect of MT for upper limb paresis after stroke. Methods: Trials included in the Cochrane review, which published data for motor function / impairment of the upper limb, were subjected to this analysis. Trials or trial arms that used MT as group therapy or combined it with electrical or magnetic stimulation were excluded. The analysis focused on the parameters mirror size, uni- or bilateral movement execution, and type of exercise. Data were pooled by calculating the total weighted standardized mean difference and the 95% confidence interval. Results: Overall, 32 trials were included. The use of a large mirror compared to a small mirror showed a higher effect on motor function. Movements executed unilaterally showed a higher effect on motor function than a bilateral execution. MT exercises including manipulation of objects showed a minor effect on motor function compared to movements excluding the manipulation of objects. None of the subgroup differences reached statistical significance. Conclusions: The results of this analysis suggest that the effects on both motor function and impairment of the affected upper limb depend on the therapy protocol. They furthermore indicate that a large mirror, unilateral movement execution and exercises without objects may be parameters that enhance the effects of MT for improving motor function after stroke.