Clinical articleReview articleMirror Box Therapy – Seeing is Believing
Introduction
In recent years, scientific research has shown that the brain is more plastic and malleable than previously suspected.1 Plasticity refers to the ability of the brain to change established neural connections. Historically, it was believed that neural pathways were secured in infancy and that adults could not change these pre-formed pathways, or develop new ones. With recent research challenging this theory, medical implications arise with regard to phantom limb pain and complex regional pain syndrome (CRPS). Phantom limb pain and CRPS are medical mysteries that support the idea that the neural connections in the brain may not be completely fixed. Mirror box therapy (MBT) and its successor, immersive virtual reality (IVR), are novel therapies for phantom limb pain, CRPS, and hemiparesis in stroke patients. These therapies may not only provide relief for thousands of patients suffering from chronic pain, but may reform the way conventional science views plasticity of the brain.2
Mirror box therapy, initially devised by Ramachandran et al.,3 is a tool that allows a person with an amputation to view a reflection of an intact limb in the visual plane of the missing limb. It was originally developed to diminish or eliminate pain and discomfort felt in phantom limbs by “tricking” the brain into believing the missing limb was actually moving. MBT has also been shown to be efficacious in CRPS and hemiparesis secondary to stroke.2 IVR is a concept that was devised with the same goals as MBT; however, it is more technologically advanced. The system detects the position and movements of the intact limb and virtually transfers the image to the space of the missing limb. The patient can then visualize, with a virtual reality screen, the intact limb in the space of the missing limb. One advantage to using IVR over MBT is that IVR allows more complete immersion into the illusion, whereas MBT requires strict focus and concentration to truly perceive the illusion as real. IVR also allows the patient to view single-handed tasks with the missing limb, something that is impossible with a mirror.3 In a preliminary study on contraindications to MBT in lower limb amputees, no absolute contraindications were found.4 However, out of 33 patients with lower limb phantom limb pain, 29 experienced adverse effects during the therapy. Most commonly, the patients experienced uncomfortable sensations during therapy, described as “confusion, dizziness, uneasiness, and sick sensations.” These side effects most often occurred when the intact limb accidentally touched the missing limb prosthesis during therapy.
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Theories on Mechanism
Although the mechanism of MBT remains unclear, there have been promising studies that attempt to define the neural basis behind its apparent success. There are several theories, which can be classified into two general categories: a primary motor cortex mechanism and a mirror neuron system mechanism.
The primary motor cortex, which is located on the posterior portion of the frontal lobe of the brain, works with premotor areas to synthesize and execute movement. Tominaga et al.5 set out to
Mirror Box Therapy and Phantom Limb Pain
Phantom limb pain is a syndrome in which pain, discomfort, nonpainful sensation, and/or movement is felt in a part of the body that no longer physically exists. Phantom limb pain occurs in at least 90% of limb amputees.8 The condition has long been recognized, but only recently has the scientific community attempted to fully understand why these symptoms occur. Some theories suggest the source of pain from chronic peripheral nerve irritation, stimulated by sensory input to the amputation stump.
Mirror Box Therapy and Complex Regional Pain Syndrome
Complex regional pain syndrome is a biological condition in which the pain experienced is disproportionate to the inciting injury. Type I is pain occurring after injury despite no obvious nerve damage, whereas Type II is pain following nerve damage even without loss of either limb.17 MBT is a promising therapy in CRPS Type I (CRPS1), as the pathophysiology is thought to be a central dysfunction in which chronic pain has persisted well beyond inflammation and repair in the limb. MBT has again
Mirror Box Therapy and Stroke Hemiparesis
Patients with stroke hemiparesis and hemineglect may also benefit from MBT. Rehabilitative therapy in hemiparesis is well established and most often encourages the use of the paralyzed part of the body to regain function. But with MBT, patients would use the functional limb in lieu of attempting to move the paralyzed limb.2 In a randomized controlled study with 36 recent stroke patients suffering from hemiparesis, Dohle et al.19 investigated whether the use of a mirror would improve motor and
Summary
Although mirror box therapy and immersive virtual reality, require further testing with randomized trials to establish efficacy, research and case studies in the 2000-2010 decade have shown great promise with these therapies in tackling phantom limb pain, CRPS, and the slow and painful recovery of paralyzed limbs secondary to stroke. In addition to physician or therapist supervised MBT, inexpensive home-based mirror therapy devices have been designed and tested and are available to the general
References (23)
- et al.
A mirror reflection of a hand modulates stimulus-induced 20-Hz activity
Neuroimage
(2009) - et al.
Mirror-induced visual illusion of hand movements: a functional magnestic resonance imaging study
Arch Phys Med Rehabil
(2009) Phantom limbs and the concept of a neuromatrix
Trends Neurosci
(1990)- et al.
Neuroscience.
(2001) Plasticity and functional recovery in neurology
Clin Med
(2005)- et al.
Investigating the efficacy of a virtual mirror box in treating phantom limb pain in a sample of chronic sufferers
Int J Disabil Hum Dev
(2006) - et al.
Mirror therapy in the rehabilitation of lower-limb amputation: are there any contraindications?
Am J Phys Med Rehabil
(2009) - et al.
Mirror therapy activates outside of cerebellum and ipsilateral M1
Neurorehabilitation
(2008) Painful memories
Eur Mol Biol Organ
(2002)- et al.
Phantom-limb pain as a perceptual correlated of cortical reorganization following arm amputation
Nature
(1995)