INTRODUCTION:
“When I look in the mirror, I see strength, learned lessons, and pride in myself”.
Viewing oneself through a mirror can evoke peculiar experiences. This has led to a novel modality called mirror therapy for a variety of pain and disability states especially involving the hands and feet, in particular phantom limb pain, stroke, complex regional pain syndrome and focal dystonia. Graded motor imagery is a sequential process of rehabilitation which provides essentially a series of brain exercises. The process is made up of (i) laterality reconstruction (ii) motor imagery and (iii) mirror therapy. Hence mirror therapy is the final stage of graded motor imagery. It is a simple, non invasive modality used for rehabilitation of the above mentioned conditions. Mirror theory is based on the evidence that action observation activates the same motor areas of the brain as action execution.
Definition of Mirror Therapy:
Mirror therapy is ground breaking non invasive treatment, in which the mirror is used to present the reverse image of a body part to the brain. This therapy was unveiled by Vilayanur S. Ramachandran and Rogers in 1996. Under this therapy, a patient is allowed to feel the imaginary movement of the removed / paralysed body part behaving as normal body through a mirror. The mirror image of the normal body part helps reorganize and integrate the mismatch between proprioception and visual feedback of the removed / paralysed body2.
Figure: 1 – Represents Mirror Therapy
Equipment used in Mirror Therapy:
Mirror Box:
In this mirror therapy mirror box is used, which is a box with one mirror in the centre where on each side of it, hands are placed in a manner that the affected limb is kept covered always and the unaffected limb is kept on the other side whose reflection can be seen on the mirror2.
Figure: 2
Figure: 3
Figure: 2 and 3 – Represents Mirror Box
Biological basis of mirror therapy – Mirror Neurons:
Our brain consists of billions of neurons and trillions of connections. Rizzolatti3 used a MIRROR NEURON to explain the fundamentals of a mirror therapy. At first, a mirror neuron was found in the monkey premotor cortex and later Rossi discovered that humans also have similar mirror neuron system in the frontal and parietal lobes. These areas are rich in motor command neurons each of which fires to orchestrate a sequence of muscle twitches to produce simple skilled movements.
These mirror neurons may be important for understanding the actions of other people, and for learning new skills by imitation.
The use of mirror visual feedback in restoring brain function:
The mirror visual feedback paves the way for a paradigm shift in the way we approach neurological disorders. Instead of resulting entirely from irreversible damage to specialized brain modules, some of them may arise from short term functional shifts that are potentially reversible. The mirror visual feedback is used in restoring brain function especially for stroke, phantom limb and complex regional pain syndrome.
1. Mirror Therapy and Stroke:
Unlearned Learned
Paralysis
Mirror Therapy
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Stroke paralysis results form actual permanent damage to the internal capsule and also from a form of learned paralysis. This learned paralysis can be potentially unlearned by using a mirror. An additional possibility is that the lesions are not always complete, there may be residue of mirror neurons that have survived but are dormant or whose activity is inhibited and does not reach threshold (motor areas may have become temporarily inactive as a result of the same mechanism as learned paralysis – a failure of visual feedback to close the loop). Mirror visual feedback might owe part of its efficacy to stimulate these neurons, thus providing the visual input to revive the motor neurons.
Stroke
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Revive Motor Neurons
Figure: 4 – Schematic representation of the Mirror Therapy and Stroke
Mirror Therapy and Phantom Limb Pain:
When an arm or leg is amputated, many patients continue to experience the vivid presence of the limb, hence the evocative term ‘Phantom limb’ coined by Mitchell (1872). Large proportion of amputees experience severe intractable pain in their phantom limb that can persist for years after amputation. The pain can be burning, cramping, crushing or lancinating. It can be intermittent or unrelenting, severely compromising the patient’s life.
Ramachandran predicted the learned paralysis theory of phantom limbs. Phantom limb pains may be induced by a conflict between visual feedback and proprioceptive representations of the amputated limb. Thus illusion or imagery movement of the amputated limb might alleviate phantom limb pain. Pain relief associated with mirror therapy may be due to the activation of mirror neurons in the hemisphere of the brain that is contra lateral to the amputated limb. These neurons fire when a person either performs an action or observes another person performing an action.
Amputations
Mismatch between visual feedback and
proprioception of the amputated limb
Severe, burning, cramping, crushing,
lancinating pain, phantom limp pain (Vivid presence of the limb)
Learned pain
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Learned immobilization
Through a mirror visual feedback
Activation of mirror neurons
Mirror neurons fire and start to imitate
the action performance through visual illusion
Learned pain, learned
immobilization Unlearned
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Patient is free from phantom limb pain
Figure: 5 – Schematic representation of the Mirror Therapy and phantom limb pain
Mirror Therapy and Reflex Sympathetic Dystrophy or Complex Regional Pain Syndrome:
This syndrome was first described by the physician Mitchell who described the phantom limbs (Mitchell 1864). The hallmark of the disorder is the persistence – indeed progressive increase in pain, swelling and inflammation in a limb long after the inciting injury has gone, despite the trivial nature of the original injury and despite the absence of any current infection or tissue damage.
Original inflammation
Any attempt to move the arm would cause severe pain
Corollary discharge from these very attempts get linked in a Hebbian memories
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Though inflammation is not there, even an accidental signal to limb evokes or amplifies the associated memories of learned pain learned immobilization
MIRROR VISUAL FEEDBACK
Conveys the visual illusion
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Painful arm is moving in response to motor commands
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Un learning of learned pain and learned immobilization
Figure: 6 – Schematic representation of the Mirror Therapy and Reflex Sympathetic Dystrophy or Complex Regional Pain Syndrome
Other uses of Mirror Therapy:
Mirror Therapy is used in
· Focal dystonias
· Dejerrine Roussy syndrome (thalamic pain)
· Trigeminal neuralgia
· Parkinsons’ disease
