Mirror therapy is a recently developed technique used to treat chronic Phantom Limb pain. Amputees sometimes feel intense pain in the region of their amputated limb, even though it no longer exists. 80% of patients report having such symptoms at some stage.
As the name suggests, the mirror therapy technique makes use of mirrors to somehow 'trick' the patient's brain into 'believing' that the limb which they see in the mirror (the unaffected one) is actually the amputated one - and can be moved painlessly at will.
A 2017 review study found that the therapy can be effective - but there is as yet no formal explanation of how it works.
Research evidence suggests that a course of treatment (four weeks) of mirror therapy may reduce chronic pain. Contraindications and side effects are few. The mechanism of action of mirror therapy remains uncertain, with reintegration of motor and sensory systems, restored body image and control over fear-avoidance likely to influence outcome. The evidence for clinical efficacy of mirror therapy is encouraging, but not yet definitive. Nevertheless, mirror therapy is inexpensive, safe and easy for the patient to self-administer.
Source : Rev Assoc Med Bras (1992). 2017 Nov;63(11):1000-1005.