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Expectation and Pain
December 07, 2011 by Dr Matthew D. Long
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Expectation and Pain
December 07, 2011 by Dr Matthew D. Long
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Expectation and Pain
December 07, 2011 by Dr Matthew D. Long
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I have written previously about the role that expectation plays in clinical practice. Indeed, mastering 'expectation management' is a core part of effective 'doctoring' and can easily make the difference between the success and failure of most forms of treatment, particularly when pain is involved. But there's more to this phenomenon than simply recognising the possibility of placebo analgesia. Recent studies have shown that a patient's expectation of treatment success influences their nociceptive system all the way from the cortex to the brainstem and spinal cord...
Most clinicians involved in treating pain would understand the concept of descending inhibition. That is, specific regions of the brainstem, such as the periaqueductal gray and the nucleus raphe magnus, project downwards to the dorsal horn of the spinal cord to inhibit nociception before it has a chance to travel to the brain and be interpreted as pain. More relevant for chiropractors, it is these brainstem regions that are thought to respond to manipulation and produce many of the benefits that we see on a daily basis (1,2,3,4). But it now appears that simply activating the brainstem modulatory centres with an adjustment is not enough to guarantee success. If the patient expects that this is going to be painful, or harmful, then you may actually increase their pain experience.
A study by Goffaux et al (5) entitled "Descending analgesia – When the spine echoes what the brain expects" looked at the phenomenon of patient expectation upon pain control. They wrote,
"These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice."
They also stated;
"This means that a valid pain treatment can lose its clinical efficacy if patients do not expect pain relief. A logical extension of this would be that previous experiences with ineffective treatments will induce expectations of failure, which may interfere with the efficacy of future treatments."
So what are the implications of this for you and your patients?
Firstly, you need to address any concerns or fears that a patient has before you start treatment. Failure to do so might mean failure to get results. You should listen to your patients and understand the beliefs that they might hold about manipulation. Secondly, you need to demonstrate to your patients your confidence and competence. The best way to do this is via a thorough clinical examination and by offering a prognosis. Patients take great comfort from knowing that you've seen their problem before. Experience equates to expertise. They also take comfort from information about how long it should take for them to feel better. So offer a prognosis based on sound science and the best available data.
Clearly factors such as patient expectation lead to huge variability between individuals and their response to treatment. This is part of the problem that researchers face when attempting to determine which treatments work best for any particular condition. It's just too hard to find a homogeneous sample of patients to study. Interestingly though, researchers are now trying to take this into account by recognising the fact that we should be attempting to determine the type of person who will respond to manipulation, rather than focussing too heavily upon the specific diagnosis that would respond. The literature now suggests that there are certain types of person who are more likely to benefit from manipulation, or acupuncture, or drugs, or surgery. The trick is finding out ahead of time what their characteristics are and then using these criteria to make an appropriate patient selection. This is the field of clinical prediction rules. We are now trying to create a set of features that will allow us to identify those who will respond to any given treatment, and this approach does seem to have promise... but that's for another article.
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
Most clinicians involved in treating pain would understand the concept of descending inhibition. That is, specific regions of the brainstem, such as the periaqueductal gray and the nucleus raphe magnus, project downwards to the dorsal horn of the spinal cord to inhibit nociception before it has a chance to travel to the brain and be interpreted as pain. More relevant for chiropractors, it is these brainstem regions that are thought to respond to manipulation and produce many of the benefits that we see on a daily basis (1,2,3,4). But it now appears that simply activating the brainstem modulatory centres with an adjustment is not enough to guarantee success. If the patient expects that this is going to be painful, or harmful, then you may actually increase their pain experience.
A study by Goffaux et al (5) entitled "Descending analgesia – When the spine echoes what the brain expects" looked at the phenomenon of patient expectation upon pain control. They wrote,
"These findings provide direct evidence that the modulation of pain by expectations is mediated by endogenous pain modulatory systems affecting nociceptive signal processing at the earliest stage of the central nervous system. Expectation effects, therefore, depend as much about what takes place in the spine as they do about what takes place in the brain. Furthermore, complete suppression of the analgesic response normally produced by descending inhibition suggests that anti-analgesic expectations can block the efficacy of pharmacologically valid treatments which has important implications for clinical practice."
They also stated;
"This means that a valid pain treatment can lose its clinical efficacy if patients do not expect pain relief. A logical extension of this would be that previous experiences with ineffective treatments will induce expectations of failure, which may interfere with the efficacy of future treatments."
So what are the implications of this for you and your patients?
Firstly, you need to address any concerns or fears that a patient has before you start treatment. Failure to do so might mean failure to get results. You should listen to your patients and understand the beliefs that they might hold about manipulation. Secondly, you need to demonstrate to your patients your confidence and competence. The best way to do this is via a thorough clinical examination and by offering a prognosis. Patients take great comfort from knowing that you've seen their problem before. Experience equates to expertise. They also take comfort from information about how long it should take for them to feel better. So offer a prognosis based on sound science and the best available data.
Clearly factors such as patient expectation lead to huge variability between individuals and their response to treatment. This is part of the problem that researchers face when attempting to determine which treatments work best for any particular condition. It's just too hard to find a homogeneous sample of patients to study. Interestingly though, researchers are now trying to take this into account by recognising the fact that we should be attempting to determine the type of person who will respond to manipulation, rather than focussing too heavily upon the specific diagnosis that would respond. The literature now suggests that there are certain types of person who are more likely to benefit from manipulation, or acupuncture, or drugs, or surgery. The trick is finding out ahead of time what their characteristics are and then using these criteria to make an appropriate patient selection. This is the field of clinical prediction rules. We are now trying to create a set of features that will allow us to identify those who will respond to any given treatment, and this approach does seem to have promise... but that's for another article.
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
References:
1. Wright A. Hypoalgesia Post-Manipulative Therapy - A Review of a Potential Neurophysiological Mechanism. Manual Therapy. 1995:6.
2. Skyba DA, Radhakrishnan R, Rohlwing JJ, Wright A, Sluka KA. Joint manipulation reduces hyperalgesia by activation of monoamine receptors but not opioid or GABA receptors in the spinal cord. Pain. 2003;106(1-2):159–168.
3. Schmid A, Brunner F, Wright A, Bachmann LM. Paradigm shift in manual therapy? Evidence for a central nervous system component in the response to passive cervical joint mobilisation. Manual Therapy. 2008;13(5):387–396.
4. Bialosky JE, Bishop MD, Price DD, Robinson ME, George SZ. The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model. Manual Therapy. 2009;14(5):531–538.
5. Goffaux P, Redmond WJ, Rainville P, Marchand S. Descending analgesia--when the spine echoes what the brain expects. Pain. 2007;130(1-2):137–143.
1. Wright A. Hypoalgesia Post-Manipulative Therapy - A Review of a Potential Neurophysiological Mechanism. Manual Therapy. 1995:6.
2. Skyba DA, Radhakrishnan R, Rohlwing JJ, Wright A, Sluka KA. Joint manipulation reduces hyperalgesia by activation of monoamine receptors but not opioid or GABA receptors in the spinal cord. Pain. 2003;106(1-2):159–168.
3. Schmid A, Brunner F, Wright A, Bachmann LM. Paradigm shift in manual therapy? Evidence for a central nervous system component in the response to passive cervical joint mobilisation. Manual Therapy. 2008;13(5):387–396.
4. Bialosky JE, Bishop MD, Price DD, Robinson ME, George SZ. The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model. Manual Therapy. 2009;14(5):531–538.
5. Goffaux P, Redmond WJ, Rainville P, Marchand S. Descending analgesia--when the spine echoes what the brain expects. Pain. 2007;130(1-2):137–143.