Mirror therapy in neurological rehabilitation
Mirror therapy in neurological rehabilitation is a sensory illusion technique classified within cognitive-behavioral therapies. It provides the individual with the illusion, through the reflection of their healthy limb in the mirror, of a normal contralateral limb. In neurological rehabilitation, the use of the mirror can be an intriguing technique to assist patients in recovering and retraining their motor and sensory functions. Several hypotheses attempt to explain the effect of mirror therapy, relying on the concept of brain plasticity, activation of mirror neurons, and the brain’s preference for utilizing visual afferents compared to somesthetic afferents (touch and proprioception). The work of Dr. Moseley’s team in Australia has significantly contributed to the widespread adoption of this technique.
Here are some ways the mirror can be utilized in this context:
Mirror for motor rehabilitation: In cases of brain injuries or neurological disorders affecting motor function, a mirror can be used to provide visual feedback during rehabilitation exercises. For example, a patient who has had a stroke and presents with hemiplegia can use a mirror to visualize the movement of their affected side during rehabilitation exercises. This can help stimulate activity in the brain regions responsible for motor control and improve coordination and muscle strength. The underlying mechanisms rely on the activation of mirror neurons. These motor neurons present in the premotor cortex activate when the person performs or imagines an action and when they observe another person performing a movement. Mirror neurons enable learning of new motor tasks through imitation. Therefore, observing the movement of the healthy hand in the mirror would activate mirror neurons that facilitate movement of the injured hand. In certain incomplete lesions, the still present mirror neurons may be “dormant” and somewhat inhibited. Mirror visual feedback would then stimulate these neurons by providing the visual input necessary for reactivation of these visuomotor neurons. The activity of mirror neurons would help bridge the gap between motor command and expected motor function, thereby unlearning paralysis.
Mirror for sensory rehabilitation: In cases where patients have sensory perception disorders, such as body schema disorders or proprioception disorders, the mirror can be used to provide visual feedback on their posture and movements. For example, a patient suffering from unilateral spatial neglect can use a mirror in addition to motor imagery to help raise awareness of their neglected side by visualizing their reflection. Additionally, hyperactivity of the healthy side may also be a consequence of brain injury. The injured hemisphere is no longer able to inhibit the healthy hemisphere, which “takes over” and exacerbates neglect. Can we then hypothesize that the subject, by observing their healthy limb move in the mirror, thus giving the illusion that it is the injured limb, stimulates activity in the affected hemisphere and consequently attenuates neglect?
Mirror for phantom limb pain and neuropathic pain: The origin of pain is believed to stem from a conflict between motor commands and sensory and proprioceptive afferents. The visual feedback provided by the mirror, by facilitating perception of the affected limb, may restore coherence between the motor system and the sensory system. Another hypothesis suggests that pain after amputation or due to paralysis of a limb may result from cortical reorganization of brain areas involved in limb control. The more significant the cortical reorganization, the more intense the pain. Mirror therapy appears to limit this pathological reorganization and consequently reduce pain by substituting for the missing limb, which can no longer send sensory messages to the cortex.
Mirror for Complex Regional Pain Syndrome: In Complex Regional Pain Syndrome (CRPS), the efficacy of mirror therapy appears to, as with phantom limb pain, rely on cortical reorganization. Another hypothesis suggests that sensory disturbances present in CRPS would modify body representations and movement programming, leading to exclusion of the limb. Mirror therapy would promote attention to the painful limb through the visual message it conveys and improve conscious perception of the limb, thereby reducing pain. Finally, building on McCabe’s work, authors propose another explanation, suggesting that mirror therapy “participates in desensitizing the painful limb by interrupting the link between limb movement and the pain caused by that movement.” In summary, experiencing painless movement, made possible by the reflection of the healthy limb in the mirror, inhibits pain associated with movement production. What the brain has memorized as painful will be “erased” thanks to the mirror.
Mirror for cognitive rehabilitation: Lastly, the mirror can also be used in cognitive rehabilitation to help patients improve their self-perception and bodily awareness following a brain injury. Working with a therapist, patients can use the mirror to explore and rebuild their body image and personal identity following physical or neurological changes.