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Proprioception, the Brain and Pain
July 23, 2013 by Dr Matthew D. Long
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Proprioception, the Brain and Pain
July 23, 2013 by Dr Matthew D. Long
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Proprioception, the Brain and Pain
July 23, 2013 by Dr Matthew D. Long
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It might often seem that science is a hard master to please. How often do we hear that a given treatment is not effective, or the effect is 'not statistically significant'? Perhaps this difficulty is partly related to our incomplete understanding of the nature of spinal disorders, particularly chronic ones. This typically leads to treatment approaches that are unfocussed - a 'shot in the dark', if you will.
As science uncovers more about the underlying mechanisms of spinal pain we are increasingly drawn to the central changes occurring within the brains of these patients. A recent paper by Wand et al (1) gives us further reason to look upwards when assessing the lower back pain patient. This study examined the ability of chronic back pain patients to localise touch sensation upon their torso and thighs when deprived of visual feedback. Not surprisingly, these patients were significantly worse at performing the task (atopognosia) than individuals without a history of back pain. So what is the relevance? As the authors stated,
"Some researchers have emphasized the role of cortical mechanisms in maintaining various chronic pain states. Specifically, it has also been argued that movement-related pain may arise as a result of incongruence between predicted and actual sensory feedback by virtue of disrupted body maps and disturbed body schema. A deficit in localization of sensory information from the back is a likely contributor to a mismatch between actual and expected sensory feedback and could contribute to ongoing movement-related pain by this mechanism. In addition, poor sensory function is likely to negatively impact on control of the spine with movement and during static tasks. This may lead to abnormal and noxious loading of spinal tissue and contribute to the maintenance of peripheral nociceptive input as a driver to the chronic pain state."
They further went on to suggest that, "Sensory discrimination training, which aims to improve sensory localization ability and is likely to sharpen the somatotopically based frame of reference, has been shown to be effective in managing phantom limb pain and CRPS. Our data suggest that these or similar approaches may be worth testing in people with CLBP."
I don't think that it is too much of a leap to suggest that spinal manipulation could be seen as a novel form of 'sensory discrimination training'.
Indeed, recent discussion in the literature about the underlying mechanisms by which manipulation exerts its effects have centred on changes to somatosensory feedback. This most likely occurs due to increases in muscle spindle firing. According to Cao et al, "Spinal manipulation, low in amplitude over a wide range of thrust durations, may produce sustained and physiologically relevant increases in resting spindle input to secondary neurons in the spinal cord following the manipulation" (2). So it just might be that chronic spinal pain patients represent a spectrum of sensorimotor integration issues that ultimately destabilise the musculoskeletal system and make it vulnerable to ongoing abnormal tissue loading, and an increased vigilance to such loading.
Decades ago chiropractors conceptualised the term 'subluxation' as a form of 'sensory disconnect' between the brain and the body. While this historical model was overly simplistic and clearly incomplete, the notion of a central dysregulation seems truer now than ever. Furthermore, the literature is slowly piecing together a picture of spinal manipulation that suggests central effects might be their most important contribution. As stated by Haavik and Murphy (3),
"It is possible that the changes in cortical somatosensory processing, sensorimotor integration and motor control that have been previously documented following high-velocity, low-amplitude spinal manipulation reflect changes in central processing of proprioceptive afferent input."
Something to think about...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
As science uncovers more about the underlying mechanisms of spinal pain we are increasingly drawn to the central changes occurring within the brains of these patients. A recent paper by Wand et al (1) gives us further reason to look upwards when assessing the lower back pain patient. This study examined the ability of chronic back pain patients to localise touch sensation upon their torso and thighs when deprived of visual feedback. Not surprisingly, these patients were significantly worse at performing the task (atopognosia) than individuals without a history of back pain. So what is the relevance? As the authors stated,
"Some researchers have emphasized the role of cortical mechanisms in maintaining various chronic pain states. Specifically, it has also been argued that movement-related pain may arise as a result of incongruence between predicted and actual sensory feedback by virtue of disrupted body maps and disturbed body schema. A deficit in localization of sensory information from the back is a likely contributor to a mismatch between actual and expected sensory feedback and could contribute to ongoing movement-related pain by this mechanism. In addition, poor sensory function is likely to negatively impact on control of the spine with movement and during static tasks. This may lead to abnormal and noxious loading of spinal tissue and contribute to the maintenance of peripheral nociceptive input as a driver to the chronic pain state."
They further went on to suggest that, "Sensory discrimination training, which aims to improve sensory localization ability and is likely to sharpen the somatotopically based frame of reference, has been shown to be effective in managing phantom limb pain and CRPS. Our data suggest that these or similar approaches may be worth testing in people with CLBP."
I don't think that it is too much of a leap to suggest that spinal manipulation could be seen as a novel form of 'sensory discrimination training'.
Indeed, recent discussion in the literature about the underlying mechanisms by which manipulation exerts its effects have centred on changes to somatosensory feedback. This most likely occurs due to increases in muscle spindle firing. According to Cao et al, "Spinal manipulation, low in amplitude over a wide range of thrust durations, may produce sustained and physiologically relevant increases in resting spindle input to secondary neurons in the spinal cord following the manipulation" (2). So it just might be that chronic spinal pain patients represent a spectrum of sensorimotor integration issues that ultimately destabilise the musculoskeletal system and make it vulnerable to ongoing abnormal tissue loading, and an increased vigilance to such loading.
Decades ago chiropractors conceptualised the term 'subluxation' as a form of 'sensory disconnect' between the brain and the body. While this historical model was overly simplistic and clearly incomplete, the notion of a central dysregulation seems truer now than ever. Furthermore, the literature is slowly piecing together a picture of spinal manipulation that suggests central effects might be their most important contribution. As stated by Haavik and Murphy (3),
"It is possible that the changes in cortical somatosensory processing, sensorimotor integration and motor control that have been previously documented following high-velocity, low-amplitude spinal manipulation reflect changes in central processing of proprioceptive afferent input."
Something to think about...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
References:
1. Wand, B. M., Keeves, J., Bourgoin, C., George, P. J., Smith, A. J., O'Connell, N. E., & Moseley, G. L. (2013). Mislocalization of sensory information in people with chronic low back pain: a preliminary investigation. The Clinical journal of pain, 29(8), 737–743. doi:10.1097/AJP.0b013e318274b320
2. Cao, D.-Y., Reed, W. R., Long, C. R., Kawchuk, G. N., & Pickar, J. G. (2013). Effects of Thrust Amplitude and Duration of High-Velocity, Low-Amplitude Spinal Manipulation on Lumbar Muscle Spindle Responses to Vertebral Position and Movement. Journal of manipulative and physiological therapeutics, 36(2), 68–77. doi:10.1016/j.jmpt.2013.01.004
3. Haavik, H., & Murphy, B. (2012). The role of spinal manipulation in addressing disordered sensorimotor integration and altered motor control. Journal of Electromyography and Kinesiology, 22(5), 768–776. doi:10.1016/j.jelekin.2012.02.012
1. Wand, B. M., Keeves, J., Bourgoin, C., George, P. J., Smith, A. J., O'Connell, N. E., & Moseley, G. L. (2013). Mislocalization of sensory information in people with chronic low back pain: a preliminary investigation. The Clinical journal of pain, 29(8), 737–743. doi:10.1097/AJP.0b013e318274b320
2. Cao, D.-Y., Reed, W. R., Long, C. R., Kawchuk, G. N., & Pickar, J. G. (2013). Effects of Thrust Amplitude and Duration of High-Velocity, Low-Amplitude Spinal Manipulation on Lumbar Muscle Spindle Responses to Vertebral Position and Movement. Journal of manipulative and physiological therapeutics, 36(2), 68–77. doi:10.1016/j.jmpt.2013.01.004
3. Haavik, H., & Murphy, B. (2012). The role of spinal manipulation in addressing disordered sensorimotor integration and altered motor control. Journal of Electromyography and Kinesiology, 22(5), 768–776. doi:10.1016/j.jelekin.2012.02.012