Mirror therapy (MT) or mirror visual feedback (MVF) is a therapy for pain or disability that affects one side of the patient more than the other side. It was invented by Vilayanur S. Ramachandran to treat post-amputation patients who had

phantom limb A phantom limb is the sensation that an amputated or missing limb is still attached. It is a chronic condition that is often resistant to treatment. When the cut ends of sensory fibres are stimulated during thigh movements, the patient feels as ...

pain (PLP). Ramachandran created a visual (and psychological) illusion of two intact limbs by putting the patient's affected limb into a "mirror box," with a mirror down the center (facing toward a patient's intact limb). The patient then looks into the mirror on the side with the good limb and makes "mirror symmetric" movements, as a symphony conductor might, or as a person does when they clap their hands. The goal is for the patient to imagine regaining control over a missing limb. Because the subject is seeing the reflected image of the good limb moving, it appears as if the phantom limb is also moving. Through the use of this artificial visual feedback, it becomes possible for the patient to "move" the phantom limb and to unclench it from potentially painful positions. Mirror therapy has expanded beyond its origin in treating phantom limb pain to the treatment of other kinds of one-sided pain or disability, for instance,

hemiparesis Hemiparesis, also called unilateral paresis, is the weakness of one entire side of the body (''wikt:hemi-#Prefix, hemi-'' means "half"). Hemiplegia, in its most severe form, is the complete paralysis of one entire side of the body. Either hemipar ...

in post-stroke patients and limb pain in patients with

complex regional pain syndrome Complex regional pain syndrome (CRPS type 1 and type 2), sometimes referred to by the hyponyms reflex sympathetic dystrophy (RSD) or reflex neurovascular dystrophy (RND), is a rare and severe form of neuroinflammatory and dysautonomic disorder ...

Post-amputation phantom limb pain

Based on the observation that phantom limb patients were much more likely to report

paralyzed Paralysis (: paralyses; also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, r ...

and painful phantoms if the actual limb had been paralyzed prior to

amputation Amputation is the removal of a Limb (anatomy), limb or other body part by Physical trauma, trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as cancer, malign ...

(for example, due to a brachial plexus avulsion), Ramachandran and Rogers-Ramachandran proposed the "learned paralysis" hypothesis of painful phantom limbs. Their hypothesis was that every time the patient attempted to move the paralyzed limb, they received

sensory feedback Feedback occurs when outputs of a system are routed back as inputs as part of a Signal chain (signal processing chain), chain of Causality, cause and effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself ...

(through

vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...

and

proprioception Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

) that the limb did not move. This feedback stamped itself into the brain circuitry through a process of

Hebbian learning Hebbian theory is a neuropsychological theory claiming that an increase in synaptic efficacy arises from a presynaptic cell's repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain synaptic plasticity, the adaptat ...

so that, even when the limb was no longer present, the brain had learned that the limb (and subsequent phantom) was paralyzed. Ramachandran created the mirror box to relieve pain by helping an amputee imagine

motor control Motor control is the regulation of movements in organisms that possess a nervous system. Motor control includes conscious voluntary movements, subconscious muscle memory and involuntary reflexes, as well as instinctual taxes. To control ...

over a missing limb. Mirror therapy is now also widely used for the treatment of motor disorders such as

hemiplegia Hemiparesis, also called unilateral paresis, is the weakness of one entire side of the body ('' hemi-'' means "half"). Hemiplegia, in its most severe form, is the complete paralysis of one entire side of the body. Either hemiparesis or hemiplegia ...

cerebral palsy Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, spasticity, stiff muscles, Paresis, weak muscles, and tremors. There may b ...

. As Deconick et al. state in a 2014 review, the mechanism of improved motor control and pain relief may differ from the mechanism of pain relief. Deconick et al., who reviewed only the effects of MVF on sensorimotor control, found that MVF can exert a strong influence on the motor network, mainly through increased cognitive penetration in action control. Although there has been much research on MVF, authors of many review articles complain about the poor methodology often used, for example, small sample sizes or lack of control groups. For this reason, one 2016 review (based on a review of 8 studies) concluded that the level of evidence was insufficient to recommend MT as a first-line treatment for phantom limb pain. A 2018 review (based on 15 studies conducted between 2012 and 2017 out of a pool of 115 publications) also criticized the quality of many reports on mirror therapy (MT) but concluded that "MT seems to be effective in relieving PLP, reducing the intensity and duration of daily pain episodes. It is a valid, simple, and inexpensive treatment for PLP." A 2018 literature review of phantom limb pain stated that mirror therapy reduced pain in randomized controlled trials.

Post-stroke hemiparesis

Treatment with mirror therapy soon expanded beyond its origin in treating phantom limb pain to treatment of other kinds of one-sided pain and loss of motor control, for example in stroke patients with

. In 1999 Ramachandran and Eric Altschuler expanded the mirror technique from amputees to improving the muscle control of stroke patients with weakened limbs. A review article published in 2016 concluded that "Mirror therapy (MT) is a valuable method for enhancing motor recovery in poststroke hemiparesis."Kamal Narayan Arya, Underlying neural mechanisms of mirror therapy: Implications for motor rehabilitation in stroke, Neurology India,2016, Volume64, Issue 1, Pages 38-4

/ref> According to a 2017 review of fifteen studies that compared mirror therapy to conventional rehabilitation for the recovery of upper-limb function in stroke survivors, mirror therapy was more successful than CR in promoting recovery. A 2018 review based on 1685 patients recovering from hemiplegic stroke found mirror therapy provided significant pain relief, while improving motor functions and activities of daily living (ADL). Thirteen out of seventeen randomized controlled trials found that MT was beneficial for post-stroke patients' legs and feet, according to a 2019 review paper. Despite considerable research, as of 2016 the underlying neural mechanisms of mirror therapy (MT) for stroke were still unclear. As Deconick et al. state in a 2014 review, the mechanism of improved motor control may differ from the mechanism of pain relief.

Complex regional pain syndrome

Mirror therapy is also a recommended therapy for

(CRPS).

Virtual reality

Virtual reality and robotics can also provide the visual illusion of regaining control of a damaged limb, but with no advantages over standard mirror therapy.

References

{{reflist, 2

External links

Ramachandran's website

WNYC - Radio Lab: Where Am I? (May 5, 2006)
downloadable segment of radio program looks at historical examples and a present-day case of phantom limbs
Ramachandran's Reith Lecture on Phantom Limbs

The Itch
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