The study of pain is a complex area, as pain isn’t just about injury. It’s also about the brain’s response to it. Thus, there is a lot we don’t yet know about things like pain sensitivity, pain habituation and the signals flying around in our brains that relate to all of it. While research continues to make advancements in this area, there is still a lot of work yet to be done. That is why a 2019 piece of research appearing in a journal dedicated to Clinical Neuroimaging is particularly interesting: it found evidence for decreased neurologic pain signature activation in people with neck pain after they received thoracic spinal manipulation.
The study is laden with significance for chiropractic care, as the area of neck pain is particularly interesting when it comes to things far removed from pain alone. Subclinical neck pain (or pain that hasn’t gotten so bad you’ve headed off to get treatment for it) can affect things like proprioception, cerebellar processing and mental task processing times. This present study was split into two parts. Part 1 used a healthy population and part 2 used a group with an “acute to subacute” level of neck pain.
In order to examine the effect of spinal manipulation on brain activity, they induced pain in the cuticle of the right index finger while examining the brain using high-tech neuroimaging equipment. Participants had a baseline pain threshold test, then they underwent spinal manipulation and redid the pain threshold test after spinal manipulation. In the first study, everyone received a High-velocity, low-amplitude (HVLA) spinal manipulation. In the second, the participants were broken up into double-blinded and randomised groups where some got the sham treatment, and some received a HVLA spinal manipulation.
The neuroimaging that examined central pain processing was accompanied by a standard numerical pain scale rating (A rating of 0 – 10 in which 0 is no pain at all and 10 is the worst pain imaginable).
While the full details of the spinal manipulation and statistical analysis of the results are available at the reference below, the key takeaways are as follows:
- All participants completed the entire study, and there were no adverse events.
- Age and gender didn’t differ significantly between groups.
- Evoked pain (brought on by the noxious stimuli to the index finger) decreased significantly post-intervention in study 1, as did the neurologic pain signature.
- In study 2 which involved the neck pain population, evoked pain didn’t change significantly, but the neurological pain signature activation did decrease significantly in the intervention group.
- This represents “preliminary evidence that [spinal manipulation] may alter the processing of pain-related brain activity within specific pain-related brain regions.”
As with every study, there are limitations to this one (which essentially offer up a plethora of opportunities for further research.) In this case, it was a small sample group, and it did not involve chronic pain patients for whom the pain-picture may be more complex. It is interesting though, that the supported brain-based biomarkers in models of neck pain and suggested that these may help us understand the mechanisms nestled in the central nervous system that respond to spinal manipulation.
The study’s authors suggested that this might help us “predict treatment response and optimize the delivery of treatment” in terms of technique, frequency and duration.
While this study certainly centres on pain and treatment, rather than optimal neural function and expression of life without subluxation, the meaning in this study certainly lends itself to both schools of thought with significant potential for explaining a central nervous system mediated response to pain management and brain function. We cannot wait to see what else comes from this line of investigation.
REFERENCES
Weber, K., Wager, T., Mackey, S., Elliot, J., Liu, W., & Sparks, C., (2019). Evidence for decreased neurologic pain signature activation following thoracic spinal manipulation in healthy volunteers and participants with neck pain. Neuroimage Clin. 2019; 24 102042, Published online Oct. DOI: 10.1016/j.nicl.2019.102042
Haavik H, and Murphy B (2011), “Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense,” JMPT Vol 34, Iss 2, Feb 2011, pp. 88-97, https://doi.org/10.1016/j.jmpt.2010.12.009
Luke M (2016), “Subclinical neck pain impairs cognitive ability which can be improved by chiropractic treatment: a four week longitudinal study with a healthy control group comparison,” Journal of Pain and Relief, DOI: 10.4172/2167-0846.C1.012, https://www.omicsonline.org/proceedings/subclinical-neck-pain-impairs-cognitive-ability-which-can-be-improved-by-chiropractic-treatment-a-four-week-longitudinal-53861.html)
Daligadu J, Haavik H, Yielder P, Baarbe J, and Murphy B (2013), “Alterations in Cortical and Cerebellar Motor Processing in Subclinical Neck Pain Patients Following Spinal Manipulation,” JMPT Vol 36, Iss 8, October 2013 pp. 527-537, https://doi.org/10.1016/j.jmpt.2013.08.003
Haavik H, Murphy B (2012), “The role of spinal manipaultion in addressing disordered sensorimotor integration and altered motor control,” J Electromyogr Kinesiol, 22(2012) pp.768-776).
Baarbe J, Holmes M, Murphy H, Haavik H, Murphy B (2016), “Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-week Longitudinal Study with a Healthy Control Group Comparison,” JMPT Vol. 39, Iss. 1, Jan 2016 pp. 23-30, https://doi.org/10.1016/j.jmpt.2015.12.002
Kelly D, Murphy B, and Backhouse D (2000), “Use of a mental rotation reaction-time paradigm to measure the effects of upper cervical adjustments on cortical processing: a pilot study,” JMPT, 23(2000), pp.246-251, DOI: https://doi.org/10.1067/mmt.2000.106099
