The advancement of chiropractic-specific stroke research is truly a cause for celebration, as those with a little bit of historical memory will attest. Not only has research found no evidence for causation when it comes to chiropractic care and cervical artery dissection, but a new stream of research is revealing the potential for chiropractic to yield significant positives when it comes to rehabilitation of stroke survivors (1,2).
A new study has appeared in the journal ‘Frontiers in Neurology’, and the title definitely gives away the punchline: “Chiropractic Spinal Adjustment Increases the Cortical Drive to the Lower Limb Muscles in Chronic Stroke Patients.” It’s the latest in an exciting stream of research emerging from our friends at the New Zealand College of Chiropractic.
It is no secret that stroke is the second leading cause of death worldwide, and for those who do survive, the extent of recovery varies. Stroke has a relatively high prevalence, affecting 200 per 100,000 people and often requires extensive rehabilitation. (1).
Stroke-induced impairment in motor function is common, with almost half of stroke survivors having limitations in walking ability. While there are many rehabilitation techniques available that are shown to enhance motor recovery post stroke, including Physical Therapy, brain-computer interface-based approaches, motor relearning techniques, awareness and evidence for the role of chiropractic care for the rehabilitation of stroke is very much in its infancy.
So far, research has indicated that spinal adjustment may be another approach to improve post-stroke motor recovery, and that it may support the plasticity of neurons of the Central Nervous System to adapt and rewire. Research has also indicated the following (2-7):
- A single session of chiro can modify central processing, inducing somatosensory processing, sensorimotor integration, motor control, and pain, suggesting chiro can rapidly affect neural and neuromuscular function in multiple ways
- The spine is the biomechanical and neurological connection between the brain (control centre) and the limbs/outer body. Changes in afferent signals from the spine alter central neural processing, impacting the motor control of the limbs.
- Strength increases have been documented to occur following chiropractic High Velocity Low Amplitude adjustments.
- Spinal adjustments resulted in significantly increased maximum motor evoked potentials (MEPs)
- The results from the current study suggest the changes after adjustment occurred at least partially at the supra-spinal level.
- Other studies have come to a similar hypothesis and showed increased muscle strength in individuals with SCSP, elite taekwondo athletes, and stroke survivors. This suggests spinal adjustment affects motor preparation and commands from the cortical regions to have more efficient control over force production.
Altogether, these studies suggest that chiropractic spinal adjustments may affect central cortical processing which thereby increases motor control efficacy. This, put simply, is big news for stroke recovery – especially when early intervention post stroke is a possibility.
So lets look at the current study, which looked at the neural plastic effects of a single session of chiropractic spinal adjustment on corticospinal excitability following spinal adjustment using MEPs in stroke survivors.
Method:
The study was a double blinded, randomised control trial with a parallel design. 29 stroke patients participated, with at least 12 weeks between the study and when they suffered the stroke which left them with some degree of lower limb impairment. To be part of the study, they had their motor performance assessed by Fugl-Meyer motor assessment scale, and had to have some kind of spinal dysfunction (for example, subluxations, but not contraindications to chiropractic care such as a fracture or a tumor).
They were divided into two groups: The control group and the chiropractic intervention group. Each session consisted of recording MEPs elicited by Transcranial Magnetic Stimulation (TMS) before and immediately after intervention.
The intervention group received High Velocity Low Amplitude adjustments to the spine. These thrusts rapidly stretch the surrounding paraspinal tissues and, in particular, the deep small paraspinal muscles. This results in a bombardment of proprioceptive input to the Central Nervous System which is thought to elicit the changes in central neural excitability and motor control changes.
MEPs were elicited using a single-pulse TMS and recorded by surface electromyography. The same chiropractor adjusted both the intervention group and the sham group. In a measure used to check the effectiveness of the study’s blinding, 14 of the 16 control group members considered the intervention they received was active, but they just got the control.
Results:
On average 5.25 levels of the spine were adjusted in the intervention group. Chiropractic spinal adjustment resulted in a significantly larger MEP size, which is noteworthy given the amount of control group members who believed themselves to be in the intervention group.
The increased MEP amplitude following adjustment implies increased excitability of motor pathways to the targeted muscle. The authors noted that:
“Furthermore, chiropractic spinal adjustment-induced changes in all the above measures occurred with minimal or no change in the H-reflex (11, 18, 28) with no change in F-wave (21, 30). The H-reflex represents the excitability of the synapse between large, fast-conducting Ia fibres and lower motor neurons (53) and is mainly altered by presynaptic inhibition and lower motoneuron excitability (54). The F wave represents the antidromic activation of a portion of the lower motor neurons at the spinal cord level (53). This indicates that the changes seen are due to supra-spinal neuroplastic changes rather than changes in spinal excitability.”
It is worth noting that increased MEP amplitudes can also indicate improved sensorimotor integration and functional connectivity in stroke survivors following spinal adjustment – all of which would be unsurprising given the chiropractic research on sensorimotor integration (See references).
But the question remains, what are the possible mechanisms behind the improvements?
Motor recovery following stroke depends on adaptive and maladaptive neuroplasticity changes. Research has indicated that subluxations can cause ongoing maladaptive neural plastic changes in the central nervous system. Thus, correcting them results in central neural plastic changes.
Therefore, it is possible that the increases in MEP following chiropractic adjustments were due to the changes in maladaptive neuroplasticity.
We are very excited about the direction this line of research is taking.
REFERENCES:
- Navid Muhammad Samran, Niazi Imran Khan, Lelic Dina, Amjad Imran, Kumari Nitika, Shafique Muhammad, Holt Kelly, Rashid Usman, Drewes Asbjørn Mohr, Haavik Heidi (2022). Chiropractic Spinal Adjustment Increases the Cortical Drive to the Lower Limb Muscle in Chronic Stroke Patients , Frontiers in Neurology. 12. https://www.frontiersin.org/article/10.3389/fneur.2021.747261
- Church E, Sieg E, Zalatimo O, Hussain N, Glantz M, Harbaugh R (2016) “Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation,” Penn State Neurosurgery Channel, http://www.cureus.com/articles/4155-systematic-review-and-meta-analysis-of-chiropractic-care-and-cervical-artery-dissection-no-evidence-for-causationretrieved 29 March 2017
- Holt K, Niazi IK, Nedergaar RW, Duehr J, Amjad I, Shafique M, Anwar MN, Ndetan H, Turker KS and Haavik H (2019), “The effects of a single session of chiropractic care on strength, cortical drive, and spinal excitability in stroke patients,” Scientific Reports, 9, Article Numbers: 2673(2019), https://www.nature.com/articles/s41598-019-39577-5retrieved 26 February 2019
- Christiansen, T.L. Niazi, I.K. Holt, K. Nedergaard, R.W. Duehr, J. Allen, K. Marshall, P. Türker, K.S. Hartvigsen, J. Haavik, H. The effects of a single session of spinal manipulation on strength and cortical drive in athletes. Eur. J. Appl. Physiol. 2018. 118;737–749
- Joo S, Lee Y, and Song C, (2018), “Immediate Effects of Thoracic Spinal Manipulation on Pulmonary Function in Stroke Patients: A Preliminary Study,”Journal of Manipulative and Physiological Therapeutics, https://doi.org/10.1016/j.jmpt.2017.12.005
- Holt K, Niazi IK, Amjad I, Kumari N, Rashid U, Duehr J, et al. The Effects of 4 Weeks of Chiropractic Spinal Adjustments on Motor Function in People with Stroke: A Randomized Controlled Trial. Brain Sci. 2021. 11(6):676.
