The role of the basal ganglia in the CRPS and in a virtual reality treatment for CRPS
I use a very effective treatment for CRPS called visual mirror imagery (VMI). VMI uses a mirror box to hide the body part with CRPS. The patient then moves the opposite side body part which is placed in front of a mirror on the box. While moving both body part simultaneously, the patient visualizes that the reflection in the mirror is actually the body part with CRPS that is being obscured. Virtual reality visual mirror feedback back (VRVMF) is an extremely effective treatment for people suffering from CRPS that uses the same mechanism (Penelle et al., 2012; Sato et al. 2010). Instead of a mirror, VRVMF uses an avatar or an identical body double that is seen in a virtual world through goggles. The difference between the patient’s body and the avatar’s or the reflection in the mirror is in the quality of movement.
When a patient moves her or his part of the body that is affected by CRPS, the movement is smaller or slower than normal due to pain. The same body part visualized by the patient as an avatar in the virtual world moves at the same speed and through the same range or motion as the patient’s opposite unaffected body part. For example a patient with CRPS in the right hand will move their right hand up and down through the wrist joint while seeing the avatar do the same movement. The patient’s will move their right hand slower and less far up and down than the same movement of her of his left hand because their right hand hurts. The avatar, however, will move her or his right hand through same distance and at the same speed as his or her left hand. As the patient continues to do the same movement while visualizing the avatar, the speed and range of motion of the affected body part (the right hand in the example) becomes the same as the virtual avatar and the pain dissipates.
VRVMF works by fixing aberrant pain processing cells in the brain that receive input from a body part affected by CRPS (Diers et al., 2014). Chronic pain changes input signals to these pain cells from a myriad of brain circuits. This is similar to power oscillations in a circuit connected to your TV. During the oscillations, the broadcast to the TV is affected and the image on the TV becomes blurred. A surge protector will restore normal input to the TV circuits and the image reverts back to a normal clear one. VRVMF is like a surge protector that uses movement to restore normal input to the pain processing cells.
One reason that normal movement will restore normal pain processing is in connections to the brain from a mid brain structure called the basal ganglia. The basal ganglia (BG) is responsible for modulating different brain areas by providing them with varying amounts of inhibition and facilitation. There are three inhibitory centers in the BG. One of these, the putamen, receives signals from the sensorimotor and supplemental motor areas of the brain that are responsible for planning and initiating movement. The second center, the caudate nucleus, receives signals from the prefrontal cortex of the brain responsible for using memories of past experiences including painful experiences to determine how to respond emotionally and physically to current situations. The third center, the nucleus accumbans connects with the limbic areas of the brain that regulate heart rate blood pressure, cognation, attention, motivation, learning and memory. The limbic areas determine the emotional response to pain (Bushnell, Ceko & Low, 2015;Nolte, 2010).
There are also two excitatory centers in the BG. The globus pallidus and the substancia nigra. Nerve pathways or striatum pass from the putamen through the globus pallidus on their way back to the sensorimotor and supplemental motor areas of the brain. Striatum from the caudate nucleus and the nucleus accumbans, both pass through the substancia nigra on their way back to the prefrontal cortex and limbic areas of the brain. Movement, pain, emotion and subsequent responses are all regulated in interconnected parts of the basal ganglia (Bushnell, Ceko & Low, 2015;Nolte, 2010).
Studies by Baliki et al. (2012) and Geha et al. (2008) provided evidence that structures in the BG of people with chronic pain were changed. Using functional MRI imaging they found that grey matter, the cell bodies of nerves was diminished in the globus palidus and caudate nucleus.
The basal ganglia is a sub brain structure that plays a role in CRPS. Restoration of normal movement input to the basal ganglia by a virtual avatar is one of the ways that virtual reality works to decrease pain in patients afflicted with CRPS.
Karuna in San Francsico http://karunavr.com is doing research studies using virtual reality to treat CRPS
Baliki, M. N., Petre, B., Torbey, S., Herrmann, K. M., Huang, L., Schnitzer, T. J., Apkarian, A. V. (2012). Corticostriatal functional connectivity predicts transition to chronic back pain. Nature Neuroscience, 15(8), 1117-1119. doi:10.1038/nn.3153; 10.1038/nn.3153
Bushnell, M.C, Ceko, M, and Low, L.A. (2015). Cognitive and emotional control of pain and its disruption in chronic pain. National Review of Neuroscience, 2013 14(7): 502–511. doi: 10.1038/nrn3516
Diers, M., Kamping, S., Kirsh, P., Rance, M., Bekrater-Bodmann, R., Foell, J… Flor, H. (2014). Illusion-related brain activations: A new virtual reality mirror box system for use during functional magnetic resonance imaging. Brain Research, 1594(12) 173-182 doi: 10.1016/j.brainres.2014.11.001
Geha, P. Y., Baliki, M. N., Harden, R. N., Bauer, W. R., Parrish, T. B., & Apkarian, A. V. (2008). The brain in chronic CRPS pain: Abnormal gray-white matter interactions in emotional and autonomic regions. Neuron, 60(4), 570-581. doi:10.1016/j.neuron.2008.08.022; 10.1016/j.neuron.2008.08.022
Nolte, J. (2010) Basal ganglia. In Essentials of the human brain electronic resource (pp145-151: 148-149). Retrieved from http://search.lib.unc.edu.libproxy.lib.unc.edu?R=UNCb7286605; Full text available via the UNC-Chapel Hill Libraries (http://vb3lk7eb4t.search.serialssolutions.com.libproxy.lib.unc.edu/?V=1.0&L=VB3LK7EB4T&S=JCs&C=TC0000536376&T=marc)