Objectives Mirror Box Therapy • How does pain affect the brain? • What is mirror box therapy/graded motor imagery? • Why do we use it? • Which patient population is the most appropriately treated with mirror box therapy Trisha Ostrander, OTD, CHT • How is mirror box therapy/GMI used and how Northwest Rehabilitation Associates does it work? The Brain The Brain Lobes/Functions • Hindbrain: brainstem and cerebellum Includes • Forebrain: lower visual cortex (occipital lobe) diencephalon, and • cerebrum • auditory cortex (temporal lobes) • Lower diecephalon: • olfactory cortex (uncus of temporal lobes) hypothalamus and thalamus • gustatory cortex (insular lobe) • primary somatosensory cortex (temperature, • Cerebrum: cortex, basal pressure, etc). ganglia, limbic system Thalamus Sensory cortex •The thalamus is situated between the cerebral cortex and the midbrain. • Its function includes relaying sensory and motor signals to the cerebral cortex 1 1 Primary sensory cortex Postcentral gyrus Sensory cortex = primary somatosensory cortex . •Located in the parietal lobe. Brain regions related to auditory, visual, olfactory, and somatosensory sensation are lateral to the lateral fissure and •It is the location of the posterior to the central sulcus. primary somatosensory cortex, the main sensory receptive Gustatory sensation – located anterior to central sulcus. area for the sense of touch. Central sulcus divides the primary motor cortex from the •Like other sensory areas, somatosensory cortex. there is a map of sensory space in this location, called the sensory homunculus. Homunculous Homunculus •A cortical homunculus is a pictorial representation of the The representation of the face anatomical divisions of the on this map on the surface of primary motor cortex and the the brain is right next to the primary somatosensory cortex. representation of the hand •The portion of the human brain directly responsible for the movement and exchange of sensory and motor information of the body. •There are two types of homunculus: sensory and motor. Homunculus distorted view Pain pathways to the brain • Distorted figure •Body region is proportional to how • Spinocortical path: thalamus -somatosensory cortex (parietal lobe) richly innervated that region is, not where pain is interpreted and intensity is interpreted (size of the to its size. area begin affected) •Because of the fine motor skills and • Know where the pain is sense nerves found in these • Spinoreticular path: brainstem -carries intensity with it particular parts of the body, they are represented as being larger on the • Spinolimbic path: limbic system-emotional part of the brain homunculus. • Hippocampus-emotion comes from memory identifies pain as particular • A part of the body with fewer kind (emotional) sensory and/or motor connections to the brain is represented to appear smaller. Psychological part of pain=misinterpreting it Need a balance between the pathways 2 2 Normal somatosensory Pathway What happens when you cut your hand? • Signals (Nociceptors) from your cut hand travel into the spinal cord through the dorsal roots. • Synapse on neurons within the dorsal horn. • Neurons then travel via spinothalmic tract into the medulla (brain stem) and synapse in the thalamus. • The thalamus is the brain’s relay center. It controls the information and relay the signal to various areas of the brain's somatosensory cortex. Neuroanatomy & Why doesn't severe pain get to brain? Pain Transmission Gate/control theory of pain •Reception •Transmission • Ronald Melzack and Patrick Wall proposed that a gating mechanism exists within the dorsal horn of the spinal cord •Modulation •Transmission • Pain can be inhibited by inhibitory neurons. •Processing & Prioritizing • These neurons help “dampen” the pain to prevent (and learning?) overwhelming the brain. •Meaning (and learning?) • Pain is dampened by fibers sending info into the pathway at • Descending inhibition the level of the spinal cord dorsal root. This prevents overload at the level of the thalamus • Other areas that dampen pain: substantia gelatinosa-opiates, brain stem -serotonin Acute and Chronic Pain NOCICEPTIVE PAIN • A nociceptor is a sensory receptor in your skin • Responds to damaging stimuli • Once activated, they transmit nerve (pain) signals to Acute: Chronic: the spinal cord and brain – Mediated by a healthy – Can refer to pain lasting • This causes the perception of pain nervous system more than 3-6 months • Nociceptive pain is usually time limited, meaning – Well defined time of – Can refer to pain that is onset and relation to not explained by physical when the tissue damage heals, the pain typically pathology findings resolves – Serves a protective role – Appears to play no protective role 3 3 NEUROPATHIC PAIN Abnormal Pain States • Examples include reflex sympathetic dystrophy / causalgia • Allodynia (nerve trauma), components of cancer pain, phantom limb pain, entrapment neuropathy, and peripheral neuropathy • Pain response to non-noxious stimuli • Often triggered by an injury, but this injury may or may not involve actual damage to the nervous system • Hyperalgesia • The pain frequently has burning or electric shock quality • Exaggerated or spontaneous response to noxious stimuli • The pain may persist for months or years beyond the apparent healing of any damaged tissues. • All associated with Central Pain Mechanisms • Pain signals no longer represent an alarm about ongoing or impending injury, instead the alarm system itself is malfunctioning. Pain causes brain changes Cortical changes and pain There is a relationship between cortical organization and pain • Impaired 2-point discrimination intensity • Loss of body schema Changes may affect hand function due to the fact that the body schema, which is influenced by pain, underlies the Inability to identify right from left performance of the hand. • Body scheme: the acquisition of an internal awareness of • Shrinkage of cortical representation of the body and the relationship of body parts to one another affected limb A Sensorimotor Performance component of occupational therapy. • Size differentiation – edema – temperature It also appears that these cortical changes can return to normal as the pain reduces Phantom limb and cortical representation Vision and Pain in “Normal” Individuals Rock & Victor, 1964 • Vision dominates touch and proprioception: If an object was made to LOOK large using a lens, while it was being palpated, it also FELT large • This is called “visual capture” • This occurs when integrating information from different senses because the brain assigns different weights to different sensory inputs depending on their statistical reliability. Vision usually dominates touch (Gibson, 1962). • Senses interact MUCH more powerfully than we previously imagined • Visual input can be used to modulate somatic pain 4 4 Brain Neuroplasticity What is neuroplasticity? • Persistent anatomical or physiological changes • RETRAIN THE BRAIN by: in a neuron that occurs during the • Repetitions development, regeneration, experimental manipulation or repeated activity across a • Challenging Activities synapse. • Rewiring occurs when new connections (synapses) are formed. • Throughout life, the brain is able to restructure itself to change by adapting. • Sensory inputs from one sense can substitute for other senses 5 R’s of Neuroplasticity and cortical Development of Mirror Box Therapy reorganization • First described by VS Ramachandran and •Remapping Hirstein in the early 1990s. •Rewiring • Discussed to restore the disruption of normal •Reorganizing interaction between intention to move the limb and the absence of appropriate sensory •Restructuring feedback •Regenerating • Began with treatment of amputation and phantom limb pain • Based on belief of neuroplasticity. Mirror Box Therapy / Graded Motor Top down training Imagery Theory Visual imagery used for relearning cognitive and planning aspect of movement • During repeated sessions, pain can be reduced because of the cortical re- Mirror and motor imagery used to re-educate organization, influencing toward normalism. or retrain the brain for basic motor skills by concentrating on the non-painful movement Smooth and controlled movements must act as example for brain to reset circuitry that mediates voluntary movement. 5 5 Mirror Neurons Mirror neurons WHAT ARE THEY? First described in the early 1990s by Rizzolatti and colleagues Mirror neurons are a special kind of brain cell that processes input to produce motor movement. Fire through both observation and imaging as well as in execution of movements. Found in the frontal lobes as well as the parietal lobes. Passive observation, goal-directed actions, and sound of action in the dark also have been shown to activate these neurons. Mirror neurons in rehab Mirror Neurons in Phantom Limb • Touch mirror neurons fire not only when you are being • Improve motor performance by using visual and touched, but also when you watch someone being touched. motor imagery • With patients with phantom limb, having them watch another person being touched on their arm may actually stimulate a • Motor imitation and motor execution excite the “touch” sensation on their missing arm. This was noted NOT, corticospinal pathway however, in the intact arm. • Movement observation may be an alternative way to • Feeling touch or pain involves more than just sensing the activate the motor system based on the mirror activation from receptors of the hand; it is a result of a neuron system