The effects and underlying mechanisms of mirror therapy – literature review

Abstract

Background: Mirror therapy is a relatively new therapeutic modality, where movement of the unaffected limb is used to facilitate performance of the affected limb. Literature review of clinical studies regarding the effectiveness of mirror therapy in different groups of patients was performed. The review focussed on randomised controlled trials and studies, which explore the underlying mechanisms of mirror therapy. Conclusions: The majority of randomised controlled trials were done in stroke patients. In these, mirror therapy improved the velocity and accuracy of the impaired upper limb movement and sensation. No significant effect was found on spasticity, gait and hand function. The effect of mirror therapy on active range of motion, hand grip, function of the upper limb and reduction of pain intensity was not fully conclusive. For complex regional pain syndrome type I, mirror therapy improved hand grip and function, and reduced pain intensity and hand oedema. There is also evidence that mirror therapy reduces pain in a phantom limb. Most of the reviewed studies included small sample size. Studies on the underlying mechanisms of mirror therapy suggested as more likely the effect of increased forced attention and motor imagery rather than increased activation of mirror neurons in healthy subjects. Probably, the underlying mechanisms of mirror therapy differ in patients with sensory-motor impairments compared to healthy subjects.