Chiropractic, Chronic Back Pain and Brain Shrinkage:


A better understanding of Alzheimer’s, Dementia, Schizophrenia, Depression and Cognitive Disorders and Chiropractic’s Role


A Review of the Mechanisms


A report on the scientific literature 


William J. Owens DC, DAAMLP

Frank Zolli DC, EdD



Reference: Studin M., Owens W., Zolli F., (2015) Chiropractic, Chronic Back Pain and Brain Shrinkage:A better understanding of Alzheimer’s, Dementia, Schizophrenia, Depression and Cognitive Disorders and Chiropractic’s Role, A Literature Review of the Mechanisms, The American Chiropractor, 37(10) 36-38, 4042, 44-45


Since its inception in 1895, Chiropractic has been focused on the spine and its role in the total health and function of the human body.  Throughout its history, the profession has moved from a “bone on nerve” model to a “biomechanical/functional” model however as we evolve (through scientific findings) in our understanding of the true nature of the chiropractic principles, we now conclusively know that chiropractic results are based on the central nervous system and the detrimental role of spinal dysfuntion in the maintenance of homeostasis and “dis-ease” in the human body.  This article bridges the gap between the foundational chiropractic principles taught by the Palmers and their predecessors and today’s breakthrough findings and the correlation between unchecked spinal dysfunction AKA chronic spine pain and its effect on the brain. 



Peterson ET. AL. (2012) reported, “The … prevalence of low back pain is stated to be between 15% and 30%, the 1-year period prevalence between 15% and 45%, and a life-time prevalence of 50% to 80%” (pg. 525). While acute pain is a normal short-lived unpleasant sensation triggered in the nervous system to alert you to possible injury with a reflexive desire to avoid additional injury, chronic pain is different. Chronic pain persists and fundamentally changes the patient’s interaction with their environment. In chronic pain it is well documented that aberrant signals keep firing in the nervous system for weeks, months, even years.1 Baliki Et. AL. (2008) stated “Pain is considered chronic when it lasts longer than 6 months after the healing of the original injury. Chronic pain patients suffer from more than pain, they experience depression, anxiety, sleep disturbances and decision making abnormalities that also significantly diminish their quality of life” (pg. 1398). Chronic pain patients also have shown to have changes in brain function in sufferers with Alzheimer’ disease, depression, schizophrenia and attention deficit hyperactivity disorder giving further insight into disease states. In addition, chronic pain has a cause and effect on the morphology of the spinal cord and the brain in particular resulting in a process termed “linear shrinkage”, which has been suggested to cause ancillary negative neurological sequella.  


Apkarian Et. Al. (2004) reported that “Ten percent of adults suffer from severe chronic pain. Back problems constitute 25% of all disabling occupational injuries and are the fifth most common reason for visits to the clinic; in 85% of such conditions, no definitive diagnosis can be made.” (pg. 10410) Apkarian Et. AL. (2011) reported “Clinically, the most relevant conditions in which human brain imaging can have a substantial impact are chronic conditions, as they remain most poorly understood and minimally treatable by existing (author’s note: medical) therapies” (pg. S53). So in essence what these authors are stating is although many people suffer from chronic spine pain, very few of them are actually diagnosed with a “medical condition” AKA an “anatomical” lesion.  The chiropractic profession has long professed the lesion is actually functional and based on aberrant spinal biomechanics [Subluxation]. 



When we look at the human population on a larger scale and from a medical perspective, we see there is a deficit in spinal care paths with resultant negative sequella of chronic back pain.  Alkarian’s conclusion was querying allopathic doctors who have little to no training or experience in treating mechanical back pain, AKA spinal dysfunction of biomechanical origin, AKA chiropractic subluxation complex.  Raissi ET. Al. (2005) reported regarding medical providers, “(92.2%) believed that musculoskeletal education had not been sufficient in general practitioner training courses. Of the respondents, 56.8% had visited at least one disabled patient during the previous month, while 11% had visited more than 10 in the same period, but 84.3% had not studied disabilities. Musculoskeletal physical examination was the most needed educational field cited by general practitioners” (pg. 167).


Day Et. Al. (2007) reported that only 26% of fourth year Harvard medical students had a cognitive mastery of physical medicine (pg. 452). Schmale (2005) reported “Incoming interns at the University of Pennsylvania took an exam of musculoskeletal aptitude and competence, which was validated by a survey of more than 100 orthopaedic program chairpersons across the country. Eighty-two percent of students tested failed to show basic competency. Perhaps the poor knowledge base resulted from inadequate and disproportionately low numbers of hours devoted to musculoskeletal medicine education during the undergraduate medical school years. Less than 1⁄2 of 122 US medical schools require a preclinical course in musculoskeletal medicine, less than 1⁄4 require a clinical course, and nearly 1⁄2 have no required preclinical or clinical course. In Canadian medical schools, just more than 2% of curricular time is spent on musculoskeletal medicine, despite the fact that approximately 20% of primary care practice is devoted to the care of patients with musculoskeletal problems. Various authors have described shortcomings in medical student training in fracture care, arthritis and rheumatology, and basic physical examination of the musculoskeletal system (pg. 251).  


With continued evidence of lack of musculoskeletal medicine and a subsequent deficiency of training in spine care, particularly of biomechanical [Subluxation] orientation, the question becomes which profession has the educational basis, training and clinical competence to manage these cases?  Let’s take a closer look at chiropractic education as a comparison. 


Fundamental to the training of doctors of chiropractic according to the American Chiropractic Association is 4,820 hours (compared to 3,398 for physical therapy and 4,670 to medicine) and receive a thorough knowledge of anatomy and physiology. As a result, all accredited doctor of chiropractic degree programs focus a significant amount of time in their curricula on these basic science courses. So important to practice are these courses that the Council on Chiropractic Education, the federally recognized accrediting agency for chiropractic education requires a curriculum which enables students to be “proficient in neuromusculoskeletal evaluation, treatment and management.” In addition to multiple courses in anatomy and physiology, the typical curriculum in chiropractic education includes physical diagnosis, spinal analysis, biomechanics, orthopedics and neurology. As a result students are afforded the opportunity to practice utilizing this basic science information for many hours prior to beginning clinical services in their internship.


To qualify for licensure, graduates of chiropractic programs must pass a series of examinations administered by the National Board of Chiropractic Examiners (NBCE). Part one of this series consists of six subjects, general anatomy, spinal anatomy, physiology, chemistry, pathology and microbiology. It is therefore mandatory for a chiropractor to know the structure and function of the human body as the study of neuromuscular and biomechanics is weaved throughout the fabric of chiropractic education. As a result, the doctor of chiropractic is expert in the same musculoskeletal genre that medical doctors are poorly trained in their doctoral education as referenced above.


Now that we have a general idea of why current musculoskeletal and spine care paths are failing, let’s examine what the negative effects are with a focus on what happens to the central nervous system when a patient is suffering from chronic pain.  The following paragraphs describe what happens to the brain as a result of chronic pain and then offers solutions based upon evidenced based studies.


Chronic Pain Affecting Brain Activity at Rest


Baliki ET. Al (2008) reported “Recent studies have demonstrated that chronic pain harms cortical areas unrelated to pain, long-term pain alters the functional connectivity of cortical regions known to be active at rest, i.e., the components of the “default mode network” (DMN). This DMN is marked by balanced positive and negative correlations between activity in component brain regions. In several disorders, however this balance is disrupted. Studying with fMRI [functional MRI] a group of chronic back pain patients and healthy controls while executing a simple visual attention task, we discovered that chronic back pain patients, despite performing the task equally well as controls, displayed reduced deactivation in several key default mode network regions. These findings demonstrate that chronic pain has a widespread impact on overall brain function, and suggest that disruptions of the default mode network may underlie the cognitive and behavioral impairments accompanying chronic pain.” (pg. 1398)


“The existence of a resting state in which the brain remained active in an organized manner, is called the ‘default mode of brain function. The regions exhibiting a decrease in activity during task performance are the component members of the “default-mode network” (DMN), which in concerted action maintain the brain resting state. Recent studies have already demonstrated that the brain default mode network is disrupted in autism, Alzheimer’ disease, depression, schizophrenia and attention deficit hyperactivity disorder, suggesting that the study of brain resting activity can be useful to understand disease states as well as potentially provide diagnostic information.”  (pg. 1398)  This is important since for the first time we are starting to see a published correlation between spinal function, chronic pain and central nervous system changes.  This is what our founders have observed yet were unable to prove.


“Thus, the alterations in the patient’s brain at ‘rest’ can result in a different default mode network organization. In turn, potential changes in the default-mode network activity could be related to symptoms (other than pain) commonly exhibited by chronic pain patients, including depression and anxiety, sleep disturbances, and decision-making abnormalities, which also significantly diminish their quality of life… chronic pain patients display a dramatic alteration in several key default-mode network regions, suggesting that chronic pain has a widespread impact on overall brain function” (pg. 1398).  This information is pointing to the fact that a doctor of chiropractic should be involved in the triage and treatment of these patients and part of a long term spinal care program. 


Baliki ET. Al (2008) continued “Consistent with extensive earlier work examining visuospatial attention tasks, dominant activations were located in posterior parietal and lateral prefrontal cortices, whereas deactivations occurred mainly within Pre-Frontal Cortex and Posterior Cingulate/Cuneate Cortexes. Although activations in chronic back pain patients’ and controls’ brains were similar, chronic back pain patients exhibited significantly less deactivations than healthy subjects in Pre-Frontal Cortex, amygdala, and Posterior Cingulate/Cuneate Cortexes.  The focus was on identifying differences in the way chronic back pain patients’ brains process information not related to pain. This is the first study demonstrating that chronic back pain patients exhibit severe alterations in the functional connectivity between brain regions implicated in the default mode network. It seems that enduring pain for a long time affects brain function in response to even minimally demanding attention tasks completely unrelated to pain. Furthermore, the fact that the observed task performance, compared with healthy subjects, is unaffected, whereas the brain activity is dramatically different, raises the question of how other behaviors are impaired by the altered brain activity” (pg. 1399).


“However, the disruption of functional connectivity observed here with increased chronic back pain duration may be related to the earlier observation of brain atrophy increasing with pain duration also in chronic back pain patients. Patient’s exhibit increased pre-frontal cortex activity in relation to spontaneous pain, in addition to dorsolateral prefrontal cortex atrophy. Therefore, the decreased deactivations described here may be related to the dorsolateral pre-frontal cortex /pre-frontal cortex mutual inhibitory interactions perturbed with time. If that is the case, it will support the idea of a plastic, time-dependent, reorganization of the brain as patients continue to suffer from chronic back pain.


Mechanistically, the early stages of this cortical reorganization may be driven by peripheral and spinal cord events, such as those that have been documented in animal models of chronic pain, whereas later events may be related to coping strategies necessary for living with unrelenting pain. It is important to recognize that transient but repetitive functional alterations can lead to more permanent changes. Accordingly, long term interference with normal activity may eventually initiate plastic changes that could alter irreversibly the stability and subsequently the conformation of the resting state networks” (pg. 1401).



Brain Region


Cingulate Cortex

Emotions, learning, motivation, memory

Insular Cortex

Consciousness, homeostasis, perception, motor control, self-awareness, cognitive function

Motor Cortex

Voluntary movements

Amygdala Cortex

Memory, decision making, emotional reactions

Somatosensory Cortex

Proprio and mechano-reception, touch, temperature, pain of the skin, epithelial, skeletal muscle, bones, joints, internal organs and cardiovascular systems

Periaqueductal Gray

Ascending and descending spinothalamtic tracts carrying pain and temperature fibers

















Chronic Pain Causing Brain “Shrinkage”


Apkarian ET. Al (2004) reported “Chronic back pain patients were divided into neuropathic, exhibiting pain because of sciatic nerve damage, and non-neuropathic groups. Patients with chronic back pain showed 5-11% less neocortical gray matter volume than control subjects. The magnitude of this decrease is equivalent to the gray matter volume lost in 10-20 years of normal aging. The decreased volume was related to pain duration, indicating a 1.3 cm3loss of gray matter for every year of chronic pain. Gray matter density was reduced in bilateral dorsolateral prefrontal cortex and right thalamus and was strongly related to pain characteristics in a pattern distinct for neuropathic and non-neuropathic chronic back pain. Our results imply that chronic back pain is accompanied by brain atrophy and suggest that the pathophysiology of chronic pain includes thalamocortical processes.


It is assumed that the cerebral cortex passively reflects spinal changes and reverts to its normal state after cessation of chronic pain. Our studies show that chronic back pain (sustained for >6 months) is accompanied by abnormal brain chemistry, mainly a reduction in theN-acetyl-aspartate-creatine ratio in the prefrontal cortex, implying neuronal loss or dysfunction in this region and reduced cognitive abilities on a task that implies abnormal prefrontal processing” (pg. 10410).


Apkarian ET. Al (2004) continued “At the whole-brain level, this reduction is related to pain duration, regionally depends on multiple pain-related characteristics, and is more severe in the neuropathic subtype. Therefore, these data present strong evidence that the pathophysiology of chronic pain includes cortical processes, and the observed changes likely constitute the physical substrate of the cognitive and behavioral properties of chronic pain” (pg. 10411).


“Thus, regional gray matter changes are strongly and specifically related to pain characteristics, and this pattern is opposite for neuropathic compared with non-neuropathic types. This dissociation is consistent with extensive clinical data showing that neuropathic pain conditions are more debilitating and have a stronger negative affect, which may be directly attributable to the larger decrease in gray matter density that we observe in the dorso-lateral pre-frontal cortex (DLPFC) of neuropathic chronic back pain patients.  Moreover, only 18% of whole-brain gray matter variance could be explained by pain duration. Therefore, a large portion of the whole-brain atrophy in chronic back pain cannot be accounted for by the measured pain characteristics, implying that there may be genetic and experiential predispositions contributing to the observed atrophy. In the DLPFC, a larger proportion of the variance could be explained by pain characteristics (40% for neuropathic chronic back pain; 80%for non- neuropathic chronic back pain), implying a tighter relationship between regional brain atrophy and perceived pain. Therefore, we suggest that the pattern of brain atrophy is directly related to the perceptual and behavioral properties of neuropathic chronic back pain.”


The observed regional pattern of atrophy is distinct from that seen in chronic depression or anxiety and shows a minimal relationship with anxiety and depression traits. Thus, it seems to be specific to chronic pain, especially because the regions showing atrophy, the thalamus and DLPFC, participate in pain perception. The DLPFC is activated in acute pain, with responses that do not code stimulus intensity. Recent evidence suggests that the DLPFC exerts “top-down” inhibition on orbitofrontal activity, limiting the magnitude of perceived pain. Thus, DLPFC atrophy may lead to a disruption of its control over orbitofrontal activity, which in turn is critical in the perception of negative affect in general and particularly in pain states. Thalamic atrophy in chronic back pain is important, because it is a major source of nociceptive inputs to the cortex and damage to this region may be a reason for the generalized sensory abnormalities commonly associated with chronic pain” (pg. 10413).


“The dorsal anterior cingulate is shown to be specifically involved in pain affect in normal subjects and exhibits decreased nociceptive signaling in various chronic pain states, which may again be caused by thalamic atrophy because the anterior thalamus is a primary input to the anterior cingulate. Therefore, we suggest that regional atrophy dictates the brain activity observed in chronic pain, and it may explain the transition from acute to chronic pain by shifting brain activity related to pain affect away from the anterior cingulate to orbitofrontal cortex.”


“It is possible that some of the observed decreased gray matter reflects tissue shrinkage [changes in extracellular space and microvascular volume may cause tissue shrinkage without substantially impacting neuronal properties], implying that proper treatment would reverse this portion of the decreased brain gray matter. The atrophy may be also attributable to more irreversible processes, such as neurodegeneration, which we favor because the main brain region involved (the DLPFC) also exhibits decreasedN-acetyl-aspartate, and decreasedN-acetyl-aspartate has been observed in most neurodegenerative conditions. Recent evidence also suggests that after nerve injury, some components of pain behavior are a consequence of hyperactivity of spinal cord microglia, and a histological study has shown a reduction in glial numbers in the cortex in major depressive disorder and bipolar disorder” (pg. 10414).

This article suggests that there is a reversible component in brain atrophy with the resolution of the chronic back pain, with strong evidence that there are some tissue structures that will be permanently damaged should the chronic pain go beyond the defined 6 months.  Clearly there are many different professions that handle the anatomical components of spine pain such as fracture, infection, disc herniation or tumor.  There is only one profession that has the education and training to treat the aberrant spinal biomechanics; chiropractic.  Since chiropractors are trained in treating/managing/triaging the anatomical lesions while also being the best suited to treat the biomechanical component, the evidence verifies that  the first contact for spine pain be a doctor of chiropractic who is also trained in differential diagnosis of underlying pathology. .


Brain Regions Effected


Apkarian ET. AL (2011) reported “The surprise was that the brain region best reflecting high magnitude of back pain was localized to the medial prefrontal cortex, extending into anterior cingulate cortex, a region not anticipated by acute pain studies. Additionally, brain areas observed for acute pain, like portions of the insula and mid- anterior cingulate cortex were only active transiently and only when the back pain magnitude was on the increase. These results are exciting because, for the first time, we are able to observe brain activity reflecting the subjective perception of the pain that chronic back pain patients come to the clinic to complain. We interpret the transient activity as a nociceptive signal from the periphery, which then is converted into a sustained emotional suffering signal in medial prefrontal cortex (pg. S54).


“Thus we can assert that, at least in this group of chronic pain patients, different brain areas encode the perceived magnitude for distinct types of pain. The prevalent expectation for brain activity in chronic pain is a sustained or enhanced activation of the brain areas already identified for acute pain. This view is partly implied by the chronic pain definition and by notions of specificity theory or labeled line theory of pain (where supraspinal organization and representation of pain is assumed to be through fixed and immutable routes). This is exactly what we donotsee. Instead these results imply that functional anatomy or physiology or some combination of both have changed in the brain of chronic back pain patients. It is also important to remember that the close relationships between fundamental properties of back pain and activity in medial prefrontal cortex and insula are correlational, and that both medial prefrontal cortex and insula respond to a long list of cognitive and emotional states (pg. S55). The morphological studies show that the brain structure undergoes changes at multiple spatial and temporal scales, which are for the most part specific to the type of chronic pain studied. That some of these changes are reversible by cessation of chronic pain speaks to the specificity of the processes and also demonstrate that chronic pain may in fact by used as a unique tool with which the dynamics of brain plasticity can be studied at multiple spatial and temporal scales” (pg. S56).


Chiropractic as a Solution for Chronic Back Pain



Peterson ET. AL. (2012) reported “investigate outcomes and prognostic factors in patients with acute or chronic low back pain (LBP) undergoing chiropractic treatment. In chronic LBP, recent studies indicate that significant improvement is often fairly rapid, usually by the fourth visit, and that patients initially receiving treatment 3 to 4 times a week have better outcomes. Patients with chronic and acute back pain both reported good outcomes, and most patients with radiculopathy (neurogenic) also improved” (pg. 525). “At 3 months, 69% of patients with chronic pain stated that they were either much better or better. This is unlikely to be due to the natural history of LBP because these patients have already passed the period when natural history occurs “(pg. 531).  A study by Tamcan et al (2010) was the only population based study of the so called “natural history” of lower back pain and the authors found the “natural history” of chronic lower back pain was not ending in resolution of symptoms but instead they documented patients moving “in and out” of a level of pain they could tolerate.   Based on the only population-based study of chronic lower back pain, the idea that the “natural history” of lower back pain ends with resolution of symptoms is a complete myth and one that is perpetuated by our present healthcare system.



Lawrence ET. AL (2008) reported “Existing research evidence regarding the usefulness of spinal adjusting… indicates the following, as much or more evidence exists for the use of SMT [spinal manipulation] to reduce symptoms and improve function in patients with chronic LBP as for use in acute and subacute LBP. The manual therapy group showed significantly greater improvements than did the exercise group for all outcomes. Results were consistent for both the short-term and the long-term” (pg. 670).



Dunn ET. AL. (2011) reported “The clinical outcomes achieved for this sample should be considered within the context of this veteran patient base, which is typically represented by older, white males with multiple comorbidities. A high percentage of overall service-connected disability was noted, with only a small percentage associated with the low back region. Considerable psychological comorbidity was found, with a high prevalence of PTSD (post-traumatic stress disorder) and depression diagnoses. PTSD and chronic pain tend to co-occur and may interact in a way that can negatively affect either disorder. A previous retrospective study of chiropractic management for neck and back pain demonstrated less improvement among those with PTSD. These points are significant because severe comorbidities and psychosocial factors lessen the likelihood of obtaining positive outcomes with conservative measures, including [chiropractic adjustments], for chronic low back pain. Mean percentages of clinical improvement exceeded the minimum clinically important difference, despite the levels of service-connected disability and comorbidity among this sample of veteran patients” (pg. 930). They went on to conclude that in spite of significant comorbidities that historically compromise positive results, 60.2% of patients met or exceeded the minimum clinically important difference for improvement (pg. 927).




Chronic pain as defined by that which has last for 6 months or longer which causes significant brain aberration in both morphology (size) and function.  The  literature suggests that this could be the precursor for many diseases as sequella of the human body’s natural reaction to prolonged pain.   Chronic back pain is one of the leading causes of chronic pain and medicine has little to no training or solutions as reported in the literature. Conversely, chiropractic has significant training and has been proven in “blinded” studies to have significant positive outcomes even in significantly adverse condition to help resolve chronic pain. As a result, the negative sequella on the brain of chronic pain, including shrinkage of the brain can be reversed through chiropractic care as the evidence has verified that once the chronic pain has resolved, the brain has the ability to return to its normal size and regain much function.



Although this evidence is strong, more research is needed and this further sets the foundation for understanding how chiropractic directly effects diseases in the human body. In addition, this also takes the chiropractic profession to the next level of understanding how and why a chiropractic adjustment works.  




  1. National Institute of Neurological Disorders and Stroke, NINDS Chronic Pain Information Page (July 2015), retrieved from:
  2. Baliki N., Geha P., Apkarian A., Chialvo D., (2008) Beyond Feeling: Chronic Pain Hurts the Brain, disrupting the Default-Mode Network Dynamics, Journal of Neurosciences 28(6) 1398-1403
  3. Apkarian V., Sosa Y., Sonty S., Levy R., Harden N., Parrish T., Gitelman D., (2004) Chronic Back Pain Is Associated with Decreased Prefrontal and Thalamic Gray Matter Density, The Journal of Neuroscience, 24(46) 10410-10415
  4. Apkarian A., Hashmi J., Baliki M., (2011) Pain and the brain: Specificity and plasticity of the brain in clinical chronic pain, Pain 152, S49-S54
  5. Raissi G., Mansoon K., Madani P., Rayegani S., (2006) Survey of General Practitioners’ attitudes Toward Physical Medicine and Rehabilitation, International Journal of Rehabilitation Research 26: 167-170
  6. Day C., Yeh A., Franko O., Ramirez M., Krupat E. (2007) Musculoskeletal Medicine: An Assessment of the Attitudes of Medical Students at Harvard Medical School, Academic Medicine 82: 452-457
  7. Schmale G. (2005) More Evidence of Educational Inadequacies in Musculoskeletal Medicine 437, 251-259
  8. Peterson C., Bolton J., Humphreys K., (2012) Predictors of Improvement in Patients With Acute and Chronic Low Back Pain Undergoing Chiropractic Treatment, Journal of Manipulative and Physiological Therapeutics, 35(7) 525-533
  9. Lawrence, D., Meeker W., Branson R., Bronford G., Cates J., Haas M., Haneline M., Micozzi M., Updyke W., Mootz R., Triano J., Hawk C., (2008) chiropractic management of low back pain and low back-related leg complaints: a literature synthesis, Journal of Manipulative and Physiological Therapeutics, 31(9) 659-674
  10. Dunn A., Green B., Formolo L., Chicoine D. (2011) Retrospective case series of clinical outcomes associated with chiropractic management for veterans with low back pain, Journal of Rehabilitation Research & Development, 48(8) 927-934
  11. Tamcan, O., Mannion, A. F., Eisenring, C., Horisberger, B., Elfering, A., & Müller, U. (2010). The course of chronic and recurrent low back pain in the general population. Pain, 150(3), 451-457.

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Published in Brain Function

How Does the Chiropractic Adjustment Work?

A Literature Review of Pain Mechanisms & Brain Function Alteration

A report on the scientific literature 


William J. Owens DC, DAAMLP


Reference: Studin M., & Owens W., (2015) How Does the Chiropractic Adjustment Work? A Literature Review of Pain Mechanisms and Brain Function Alteration, The American Chiropractor 37(8)  30, 32-34, 36-38, 40, 42-43


Were D.D. and B.J. Palmer right with their bone on nerve theory?According to Charles A. Lantz, DC. PhD. Director of Research, Life Chiropractic College West (2015), Montgomery and Nelson cited the context within which medical authors in the mid- to late 19th century referred to subluxation, one that was similar to how D.D. Palmer later would:


A vertebra is said to be displaced or luxated when the joint surfaces are entirely separated. Sub-luxation is a partial or incomplete separation: one in which the articulating surfaces remain in partial contact. This latter condition is so often referred to and known by chiropractors as sub-luxation. The relationship existing between bones and nerves are so nicely adjusted that anyone of the 200 bones, more especially those of the vertebral column, cannot be displaced ever so little without impinging upon adjacent nerves. Pressure on nerves excites, agitates, creates an excess of molecular vibration, whose effects, when local, are known as inflammation, when general, as fever. A subluxation does not restrain or liberate vital energy. Vital energy is expressed in functional activity. A subluxation may impinge against nerves, the transmitting channel may increase or decrease the momentum of impulses, not energy. http://www.chiro. org/LINKS/FULL/A_Review_of_the_Evolution.shtml#Citation_7


Lance (2015) also reported, "According to BJ Palmer, a subluxation represented a displaced bone that impinged on a nerve, thus interfering with the transmission of vital nerve energy (or, more specifically, the transmission of ‘mental impulses.’)” ( Evolution. shtml)


For over a century, doctors of chiropractic have been explaining chiropractic by teaching patients and the medical community that there are bones compressing/irritating spinal nerves. The ensuing nervous system dysfunctions have negative effects on the function of peripheral nervous systems, central nervous systems and patients’ overall ability to maintain homeostasis. Essentially, they go into states of dis-ease.  These discussions were in large part due to the teachings of D.D. Palmer and B.J. Palmer as previously cited. Based on the results rendered in chiropractic offices across the country and in a patient-driven model of success, the general consensus in both private practice and chiropractic academia had been to maintain status quo and simply teach what has worked in the absence of conclusive evidence, particularly in light of a lack of serious governmental funding and support for chiropractic research.  In addition, dogma has also created blinders for many, as evidence evolves to further chiropractic and its understanding, application and expansion.


Over the last 10-15 years, research has been published by the scientific community that has begun to verify that D.D. and B.J. Palmer’s hypotheses were fundamentally correct, while clarifying the specific physiological mechanisms related to chiropractic’s ability to alleviate pain.  As a result of initially studying pain mechanisms, contemporary research has also begun to set the foundation for understanding why chiropractic works with systemic and autonomic dysfunction and potential disease treatment through the adjustment – central nervous system connection. It is the understanding of that connection with pain that is helping people to begin to understand the full impact of the chiropractic spinal adjustment and render the evidence to help more get well.




Coronado et al. (2012) reported that, “Reductions in pain sensitivity, or hypoalgesia, following SMT [spinal manipulative therapy or the chiropractic adjustment] may be indicative of a mechanism related to the modulation of afferent input or central nervous system processing of pain” (p. 752). “The authors theorized the observed effect related to modulation of pain primarily at the level of the spinal cord since (1) these changes were seen within lumbar innervated areas and not cervical innervated areas and (2) the findings were specific to a measure of pain sensitivity (temporal summation of pain), and not other measures of pain sensitivity, suggesting an effect related to attenuation of dorsal horn excitability and not a generalized change in pain sensitivity” (Coronado et al., 2012, p. 752). These findings indicate that a chiropractic spinal adjustment affects the dorsal horns at the root levels which are located in the central nervous system.  This is the beginning of the “big picture” since once we identify the mechanism by which we can positively influence the central nervous system, we can then study that process and its effects in much more depth.    


One of the main questions asked by Corando et al. (2012) “…was whether SMT (chiropractic adjustments) elicits a general response on pain sensitivity or whether the response is specific to the area where SMT is applied. For example, changes in pain sensitivity over the cervical facets following a cervical spine SMT would indicate a local and specific effect while changes in pain sensitivity in the lumbar facets following a cervical spine SMT would suggest a general effect. We observed a favorable change for increased PPT [pressure pain threshold] when measured at remote anatomical sites and a similar, but non-significant change at local anatomical sites. These findings lend support to a possible general effect of SMT beyond the effect expected at the local region of SMT application (p. 762).


The mechanisms of SMT are theorized to result from both spinal cord mediated mechanisms and supraspinal mediated mechanisms [brain]. A recent model of the mechanisms of manual therapy suggests changes in pain related to SMT result from an interaction of neurophysiological responses related to the peripheral nervous system and the central nervous system at the spinal and supraspinal level” (Coronado et al., 2012, p. 762).  This demonstrates that the chiropractic adjustment influences the peripheral nervous system and the central nervous system.  “Collectively, these studies provide evidence that SMT has an immediate effect on reducing pain sensitivity, most notably at the remote region of stimulus assessment with similar results in clinical and healthy populations” (Coronado et al., 2012, p. 763). 




Reed, Pickar, Sozio, and Long (2014) reported:

…forms of manual therapy have been clinically shown to increase mechanical pressure pain thresholds (i.e., decrease sensitivity) in both symptomatic and asymptomatic subjects.Cervical spinal manipulation has been shown to result in unilateral as well as bilateral mechanical hypoalgesia. Compared with no manual therapy, oscillatory spinal manual therapy at T12 and L4 produced significantly higher paraspinal pain thresholds at T6, L1, and L3 in individuals with rheumatoid arthritis. The immediate and widespread hypoalgesia associated with manual therapy treatments has been attributed to alterations in peripheral and/or central pain processing including activation of descending pain inhibitory systems.

Increasing evidence from animal models suggests that manual therapy activates the central nervous system and, in so doing, affects areas well beyond those being treated. (p. 277)

Reed et al. (2014) also reported:


The finding that only the higher intensity manipulative stimulus (ie, 85% BW [body weight] vs 55% BW or control) decreased the mechanical sensitivity of lateral thalamic neurons to mechanical trunk stimulation coincides with other reports relating graded mechanical or electrical stimulus intensity to the magnitude of central inhibition…

Several clinical studies indicate that spinal manipulation [chiropractic spinal adjustment] alters central processing of mechanical stimuli evidenced by increased pressure pain thresholds and decreased pain sensitivity in asymptomatic and symptomatic subjects following manipulation. (p. 282)


Thalamus. (2015). Wikipedia. Retrieved from http://en.wikipedia.orgwiki/Thalamus

The thalamus has multiple functions. It may be thought of as a kind ofhubof information. It is generally believed to act as a relay between different subcortical areas and thecerebral cortex. In particular, every sensory system (with the exception of theolfactory system) includes a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area. For the visual system, for example, inputs from theretinaare sent to thelateral geniculate nucleusof the thalamus, which in turn projects to thevisual cortexin theoccipital lobe. The thalamus is believed to both process sensory information as well as relay it—each of the primary sensory relay areas receives strong feedback connections from the cerebral cortex. Similarly themedial geniculate nucleusacts as a keyauditoryrelay between theinferior colliculusof themidbrainand theprimary auditory cortex, and the ventral posterior nucleusis a keysomatosensoryrelay, which sends touch andproprioceptiveinformation to theprimary somatosensory cortex.


The thalamus also plays an important role in regulating states ofsleep and wakefulness.Thalamic nuclei have strong reciprocal connections with the cerebral cortex, formingthalamo-cortico-thalamic circuitsthat are believed to be involved withconsciousness. The thalamus plays a major role in regulating arousal, the level of awareness, and activity (“Thalamus,”


This indicates that the chiropractic spinal adjustment reduces pain by effecting the thalamus and descending central pain pathways, while mobilization does not show evidence of having the same effect.  In addition, with our current knowledge of the chiropractic adjustment effecting the thalamus, we can begin to offer an explanation of how the first historically reported chiropractic adjustment by D.D. Palmer helped Harvey Lilard regain his hearing. 



Mohammadian, Gonsalves, Tsai, Hummel, and Carpenter (2004) investigated “the hypoalgesic effects of a single SMT on acute inflammatory reactions and pain induced by capsaicin [hot pepper extract]. These effects were assessed by measuring both sensory (allodynia [central nervous system pain], hyperalgesia, spontaneous pain intensity) and local vascular parameters (blood flow)” (p. 382). They reported “As expected, topical capsaicin induced primary hyperalgesia in the application area and secondary hyperalgesia outside that area. While the local vascular parameter blood flow was not affected by a single SMT [spinal manual therapy], the results indicated that sensory parameters (spontaneous pain perception and areas of both secondary hyperalgesia and allodynia) were significantly altered after spinal manipulation compared with N-SMT [non-spinal manipulative therapy]. These results clearly demonstrated that in contrast to the N-SMT condition, a single spinal manipulation triggered hypoalgesic effects” (Mohammadian et al., 2004, p. 385).


“In the present study, local blood flow was not affected by a single SMT. However, significant changes were observed on sensory parameters, supporting the hypothesis of centrally mediated effects of a single SMT. It is well known that secondary hyperalgesia appears to be due to central sensitization of the spinal dorsal horn neurons,while primary hyperalgesia is caused by nociceptor sensitization. It has also been discussed that mechanisms underlying allodynia are centrally mediated.Our findings also confirm the view that the hypoalgesic effects of a single SMT might be due to central modulation. These effects could also be explained as a result of a stress reaction caused by spinal manipulation treatment…Other studies discussed thatspinal manipulation [chiropractic spinal adjustments] stimulates mechanoreceptors of the spinal joints, resulting in afferent discharges and subsequently causing inhibitory reactions on the dorsal horn neurons.Vicenzino et al. demonstrated also a strong correlation between hypoalgesic and sympathoexcitatory effects, suggesting that a central control mechanism might be activated by manipulative therapy… previous studies as well as the present investigation…indicate that hypoalgesic effects of spinal manipulation are more likely mediated through central modulation” (Mohammadian et al., 2004, p. 386).  This study suggests that the chiropractic spinal adjustment affects the nociceptors and the mechanoreceptors at the joint level causing central modulation of an effect at the cord and/or brain level(s) and pain reductions in multiple areas as a result.



Gay, Robinson, George, Perlstein, and Bishop (2014) reported, “With the evidence supporting efficacy of MT [manual therapy or chiropractic spinal adjustments] to reduce pain intensity and pain sensitivity, it is reasonable to assume that the underlying therapeutic effect of MT is likely to include a higher cortical component” (p. 615).   It is in this place in particular that chiropractic must lead in both clinical application and academic processes such as formal continuing education lectures and research.


In the study conducted by Gay et al. (2014), “…pain-free volunteers processed thermal stimuli applied to the hand before and after thoracic spinal manipulation (a form of MT).  What they found was that after thoracic manipulation, several brain regions demonstrated a reduction in peak BOLD [blood-oxygen-level–dependent] activity. Those regions included the cingulate, insular, motor, amygdala and somatosensory cortices, and the PAG [periaqueductal gray regions]” (p. 615). In other words, thoracic adjustments produced direct and measureable effects on the central nervous system across multiple regions, which in the case of the responsible for the processing of emotion (cingulate cortex, aka limbic cortex) are regarding the insular cortex which also responsible for regulating emotion as well has homeostasis. The motor cortex is involved in the planning and execution of voluntary movements, the amygdala’s primary function is memory and decision making (also part of the limbic system), the somatosensory cortex is involved in processing the sense of touch (remember the homunculus) and, finally, the periaqueductal gray is responsible for descending pain modulation (the brain regulating the processing of painful stimuli).


Brain Region


Cingulate Cortex

Emotions, learning, motivation, memory

Insular Cortex

Consciousness, homeostasis, perception, motor control, self-awareness, cognitive function

Motor Cortex

Voluntary movements

Amygdala Cortex

Memory, decision making, emotional reactions

Somatosensory Cortex

Proprio and mechano-reception, touch, temperature, pain of the skin, epithelial, skeletal muscle, bones, joints, internal organs and cardiovascular systems

Periaqueductal Gray

Ascending and descending spinothalamtic tracts carrying pain and temperature fibers


This is a major step in showing the global effects of the chiropractic adjustment, particularly those that have been observed clinically, but not reproduced in large studies.  “The purpose of this study was to investigate the changes in FC [functional changes] between brain regions that process and modulate the pain experience after MT [manual therapy]. The primary outcome was to measure the immediate change in FC  across brain regions involved in processing and modulating the pain experience and identify if there were reductions in experimentally induced myalgia and changes in local and remote pressure pain sensitivity” (Gay et al., 2014, p. 615).  Simply put, can the processing of pain be modulated or regulated from an external force without the use of pharmacy or surgery? 


“Within the brain, the pain experience is subserved by an extended network of brain regions including the thalamus (THA), primary and secondary somatosensory, cingulate, and insular cortices.Collectively, these regions are referred to as the pain processing network (PPN) and encode the sensory discriminate and cognitive and emotional components of the pain experience.Perception of pain is dependent not merely on the neural activity within the PPN [pain processing network] but also on the flexible interactions of this network with other functional systems, including the descending pain modulatory system” (Gay et al., 2014, p. 617).  This is part of the reason why some patients experience pain differently than others.  Some have anxiety, depression and are at a loss to function while others can “ignore” the pain and maintain an adequate functional level as a productive member of society.  Pain is deeply tied to the most primitive regions of the central nervous system and it appears (as chiropractors have observed clinically for 116 years) that therapeutically speaking, we can have an influence on these higher centers with little or no side-effects.   


Gay et al. (2014) went on to report, “This study assessed the relationship of brain activity between regions of the PPN [pain processing network] before and after MT [manual therapy or chiropractic spinal adjustments]. Using this approach, we found common and treatment-dependent changes in FC [functional changes]…Our study is unique in our neurophysiologic measure because we used resting-state fMRI [functional MRI] in conjunction with FC [functional change] analyses. Our results are in agreement with studies that have found immediate changes using other neurophysiologic outcomes, such as Hoffman-reflex and motor-neuron excitability, electroencephalography with somatosensory-evoked potentials, transcranial magnetic stimulation with motor evoked potentials, and task-based fMRI with peak BOLD response” (p. 619 and 624).  This study concludes that chiropractic spinal adjustments create functional changes in multiple regions of the brain based upon multiple outcome measures.   In the study by Gay et al. 2014), this was measureable and reproducible. In addition, this has far reaching effects in setting the foundation for understanding how the adjustment works in systemic and possibly autonomic changes by being able to measure and reproduce functional changes within the brain as direct sequellae.




Daligadu, Haavik, Yielder, Baarbe, and Murphy (2013) also reported that “Numerous studies indicate that significant cortical plastic changes are present in various musculoskeletal pain syndromes.In particular, altered feed-forward postural adjustments have been demonstrated in a variety of musculoskeletal conditions including anterior knee pain, low back pain,and idiopathic neck pain.Furthermore, alterations in trunk muscle recruitment patterns have been observed in patients with mechanical low back pain” (p. 527). What this means is that there are observable changes in the function of the central nervous system seen in patients with musculoskeletal conditions.  That is something that chiropractors have observed clinically and shows the medical necessity for chiropractic care for both short and long term management as well as in the prevention of pain syndromes. 


Daligadu et al. (2013) stated the following:


There is also evidence in the literature to suggest that muscle impairment occurs early in the history of onset of spinal complaints,and that such muscle impairment does not automatically resolve even when pain symptoms improve. This has led some authors to suggest that the deficits in proprioception and motor control, rather than the pain itself, may be the main factors defining the clinical picture and chronicity of various chronic pain conditions.

Furthermore, recent evidence has demonstrated that spinal manipulation can alter neuromuscular and proprioceptive function in patients with neck and back pain as well as in asymptomatic participants. For instance, cervical spine manipulation has been shown to produce greater changes in pressure pain threshold in lateral epicondylalgia than thoracic manipulation; and in asymptomatic patients, lumbar spine manipulation was found to significantly influence corticospinal and spinal reflex excitability. “Interestingly, Soon et al did not find neurophysiological changes following mobilization on motor function and pressure pain threshold in asymptomatic individuals, perhaps suggesting that manipulation [chiropractic spinal adjustments], as distinct from mobilization, induces unique physiological changes. There is also accumulating evidence to suggest that chiropractic manipulation can result in changes to central nervous system function including reflex excitability, cognitive processing, sensory processing, and motor output.There is also evidence in SCNP [sub-clinical neck pain] individuals that chiropractic manipulation alters cortical somatosensory processingand elbow joint position sense.This evidence suggests that chiropractic manipulation may have a positive neuromodulatory effect on the central nervous system, and this may play a role in the effect it has in the treatment of neck pain. It is hoped improving our understanding of the neurophysiological mechanisms that may precede the development of chronic neck pain in individuals with SCNP will help provide a neurophysiological marker of altered sensory processing that could help determine if an individual is showing evidence of disordered sensorimotor integration and thus might benefit from early intervention to prevent the progression of SCNP into more long-term pain states.  (p. 528)


The authors went on to state, “Previous work using paired-pulse transcranial magnetic stimulation (TMS) of the motor cortex has indicated that cervical spine manipulation can alter sensorimotor integration of the upper limb by decreasing the amount of short-interval intracortical inhibition (SICI).A recent somatosensory evoked potential (SEP) study involving dual SEPs from the median and ulnar nerves demonstrated that cervical manipulation of dysfunctional areas in patients with a history of reoccurring neck pain or stiffness was able to affect sensorimotor integration…spinal manipulation altered the way the central nervous system responded to the motor training task” (Daligadu et al., 2013, p. 528).


Furthermore, the authors added, “…altered afferent input from the neck due to joint dysfunction leads to disordered sensorimotor integration within the cerebellum and a subsequent derangement in motor commands to the upper limb. The cerebellum plays a fundamental role in detecting the encoded afferent signal and relaying this information as part of the body schema. When the input signal is no longer encoded as a result of joint dysfunction and altered afferent input, the cerebellum must adjust to new encodings that dictate the body schema and affect proper execution of the motor task” (p. 529).


“Motor sequence learning tasks have been previously shown to induce plasticity within the circuitry of both the motor cortexand the cerebellum…Neck manipulation [chiropractic spinal adjustments] has also been shown to provide a modulatory effect on the motor cortex by reducing the amount of intracortical inhibition.” (Daligadu et al., 2013, p. 533).


“This study further adds to the literature by demonstrating an alteration in cerebellar modulation of motor output in SCNP [sub-clinical neck pain] patients when they received a manipulation-based chiropractic treatment before performing motor sequence learning.In the healthy control group, there was no change in CBI seen following motor sequence learning alone” (Daligadu et al., 2013, p. 534).


“If the motor sequence learning task had a significant effect on the cerebellum in this group of participants due to their neck pain and altered sensorimotor integration, then it is possible that a decreased level of CBI [cerebellar inhibition] output to the motor cortex would result in an increase in SICI [short-intracortical inhibition]” (Daligadu et al., 2013, p. 534). The significance of this study is that it suggests that the chiropractic spinal adjustment improves not just neck dysfunction, but through plasty changes in the cerebellum, there is resultant motor learning and increased function. 




Based upon the scientific evidence, chiropractic spinal adjustments stimulate mechanoreceptors and nociceptors of the spinal joints resulting in afferent discharges and subsequently causing central modulation with an effect at the cord and brain levels. This causes pain reductions and secondary hyperalgesia (pain reduction in remote regions) which appears to be due to central sensitization of the spinal dorsal horn neurons,while primary hyperalgesia is caused by nociceptor sensitization.


This verifies that chiropractic adjustments influence the peripheral nervous system and the central nervous system. In the central nervous system, chiropractic spinal adjustments reduce pain by effecting the thalamus and descending central pain pathways.


Chiropractic spinal adjustments also create functional changes in multiple regions of the brain based upon multiple outcome measures that are measureable and reproducible. The areas of the brain affected by chiropractic adjustments effect the following functions: emotions, learning, motivation, memory, consciousness, homeostasis, perception, motor control, self-awareness, cognitive function, voluntary movements, decision making, touch, temperature, pain of the skin- epithelial tissue-skeletal muscles-bones-internal organs and cardiovascular system. This has far reaching effects in setting the foundation for understanding how the adjustment works in systemic and autonomic changes by being able to measure and reproduce functional changes within the brain as direct sequellae.


The evidence also reveals that only chiropractic adjustments (high velocity-low amplitude) render these findings and mobilization of joints conclusively do not. In addition, muscle impairment does not automatically improve with symptoms abating creating the necessity for both short and long-term care. This indicates that the deficits in proprioception and motor control, rather than the pain itself, may be the main factors defining the clinical picture and chronicity of various chronic pain conditions.



1. Lantz, C. A. (1995). A review of the evolution of chiropractic concepts of subluxation. Topics in Clinical Chiropractic, 2(2). Retrieved from

2. Coronado, R. A., Gay, C. W., Bialosky, J. E., Carnaby, G. D., Bishop, M. D., & George, S. Z. (2012). Changes in pain sensitivity following spinal manipulation: A systematic review and meta-analysis. Journal of Electromyography Kinesiology, 22(5), 752-767.

3. Reed, W. R., Pickar, J. G., Sozio, R. S., & Long, C. R. (2014). Effect of spinal manipulation thrust magnitude on trunk mechanical activation thresholds of lateral thalamic neurons. Journal of Manipulative and Physiological Therapeutics, 37(5), 277-286.

4. Thalamus. (2015). Wikipedia. Retrieved from

5. Mohammadian, P., Gonsalves, A., Tsai, C., Hummel, T., & Carpenter, T. (2004). Areas of capsaicin-induced secondary hyperalgesia and allodynia are reduced by a single chiropractic adjustment: A preliminary study. Journal of Manipulative and Physiological Therapeutic, 27(6), 381-387.

6. Gay, C. W., Robinson, M. E., George, S. Z., Perlstein, W. M., & Bishop, M. D. (2014). Immediate changes after manual therapy in resting-state functional connectivity as measured by functional magnetic resonance imaging in participants with induced low back pain. Journal of Manipulative and Physiological Therapeutics, 37(9), 614-627.

7. Daligadu, J., Haavik, H., Yielder, P. C., Baarbe, J., & Murphy, B. (2013). Alterations in coritcal and cerebellar motor processing in subclinical neck pain patients following spinal manipulation. Journal of Manipulative and Physiological Therapeutics, 36(8), 527-537.



Dr. Mark Studin is an Adjunct Associate Professor of Chiropractic at the University Of Bridgeport College Of Chiropractic, an Adjunct Assistant Professor of Clinical Sceinces at Texas Chiropractic College and a clinical presenter for the State of New York at Buffalo, School of Medicine and Biomedical Sciences for post-doctoral education, teaching MRI spine interpretation and triaging trauma cases. He is also the president of the Academy of Chiropractic teaching doctors of chiropractic how to interface with the legal community (, teaches MRI interpretation and triaging trauma cases to doctors of all disciplines nationally and studies trends in healthcare on a national scale ( He can be reached at 631-786-4253.


Dr. Bill Owens is presently in private practice in Buffalo and Rochester NY and has created chiropractic as the primary spine care referral for the primary care medical community and emergency rooms in both regions.  He is an Associate Adjunct Professor at the State University of New York at Buffalo School of Medicine and Biomedical Sciences and is an Adjunt Assistant Professor of Clinical Sceinces at the University of Bridgeport, College of Chiropractic and Texas Chiropractic College.  He also works directly with doctors of chiropractic to help them build relationships with medical providers in their community. He can be reached at or 716-228-3847  

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