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Blind-Spot Mapping, Cortical Function, and Chiropractic Manipulation

Steven Novella recently wrote about so-called “chiropractic neurology” and its most outspoken proponent, Ted Carrick.  In 2005 I published an article in The Scientific Review of Alternative Medicine (Vol 9, No 1, p. 11-15) entitled “Blind-Spot Mapping, Cortical Function, and Chiropractic Manipulation.” It was an analysis of a study Carrick had published.

Carrick read a shorter, popularized version of my critique in Skeptical Inquirer and responded with a diatribe that was inaccurate, distorted what I had said, and accused me of fraud, deception, and mis-representation.  He failed to offer a credible rebuttal of my specific criticisms; and, in my opinion, showed that he failed to understand some of my points. He referred to me as “Ms. Hall” and suggested that I was psychotic. He characterized my e-mail correspondence with him as “bizarre, rude, and offensive.” It was none of those, and I have copies of the e-mails to prove it. Carrick says he “forwarded it to the legal council for the American Chiropractic Association for review.”  Now that strikes me as bizarre.

I am re-publishing the entire text of my article here as an instructive example of what passes for science in the chiropractic neurology community. Readers can judge for themselves whether my critique amounts to fraud and whether I am showing signs of psychosis, whether Carrick is a good scientist and whether his reply to my critique was appropriate.

 

Title:  Blind-Spot Mapping, Cortical Function, and Chiropractic Manipulation

ABSTRACT:

Background: A technique of blind-spot mapping is being used by chiropractors to determine hemispheric dominance and to map cortical function; the findings are being used clinically to guide unilateral cervical spine manipulations.

Objective: The objective of this paper is to evaluate the evidence for the assertions that (1) large numbers of normal people have an enlarged blind spot on one side; (2) mapping the blind spot is equivalent to mapping brain function, and (3) spinal manipulation alters the size of the blind spot by altering brain function.

Design: A review of the literature found only 1 pertinent study; this study was analyzed for flaws and for quality of evidence.

Results: Serious methodological and logical flawswere found that invalidate the conclusions of the study.

Conclusion: The evidence for a high incidence of enlarged blind spots is unconvincing. There is no evidence that blind-spot mapping reflects cortical function or that manipulation can affect the size of the blind spot by altering brain function.

BACKGROUND

The blind spot is the area of the retina where the optic nerve enters the eye, where there are no photoreceptors. In monocular vision, it represents a small area of the visual field, about halfway between the midpoint and the lateral edge, where no visual input is received. In binocular vision, that area is visible to the opposite eye. The brain fills in the missing information to create the illusion of an uninterrupted visual field. Ophthalmologists routinely map the blind spots when testing visual fields for clinical diagnosis and follow-up. Until 1997, no one had observed any significant difference in blind-spot size between the left and right eyes in the absence of retinal disease. In that year, a study by Frederick Carrick, DC, PhD, titled “Changes in Brain Function after Manipulation of the Cervical Spine,” was published in the Journal of Manipulative and Physiological Therapeutics. (1) Studying 500 volunteers, he reported that all had a significant enlargement of 1 blind spot and that it returned to normal size following selective unilateral manipulation of the cervical spine.

The blind-spot-mapping technique described by Dr. Carrick is now being widely used by chiropractors and others. The technique is being taught at postgraduate chiropractic neurology seminars. Proponents claim to be mapping brain function, and to be able to affect brain function by manipulating the spine. A sample newspaper ad reads:

DO YOU HAVE A GOOD BRAIN OR A BAD BRAIN? ONE SIMPLE TEST MAY TELL YOu. Balance Problem? Learning Disability? Pain? Eye Problems? You name it. It could all be in your head. Researchers concluded: “Accurate reproducible maps of cortical (i.e. brain) responses can be used to measure the neurological consequences of spinal joint manipulation. Cervical manipulation activates specific neurological pathways. Manipulation of the cervical spine may be associated with an increase or a decrease in brain function depending upon the side of the manipulation and the cortical hemisphericity (i.e., side of decreased brain function) of a patient. Call Today for a FREE Brain Function Exam. (2)

Chiropractic originally claimed that all disease resulted from the effect of bone displacements (subluxations) on the nervous system. (3) Some chiropractors now limit their practice to the musculoskeletal system; others still claim to be able to treat other systems of the body. Ear infections, asthma, and constipation are among the conditions treated by chiropractors. (4) Neuroanatomy, as it is presently understood, tells us that spinal manipulation should not affect the brain or other structures within the skull; chiropractors believe it does, and they have been seeking scientific proof of that belief for over a century. The 1997 study by Dr. Carrick is considered by some to constitute that proof. The issue is an important one: if manipulation is proven to have an effect on brain function, there will be reason to accept chiropractic as a part of mainstream medicine and to teach it in medical schools.

OBJECTIVE

The evidence for blind-spot mapping was evaluated to determine if it supported claims that

  1. large numbers of normal people have an enlarged blind spot on one side;
  2. mapping the blind spot is equivalent to mapping brain function;
  3. spinal manipulation affects the size of the blind spot by altering brain function.

DESIGN

The medical literature and the Internet were searched and the author of the original 1997 study was contacted in an attempt to locate all published literature on the subject. Ten letters to the editor followed the original study in the Journal of Manipulative and Physiological Therapeutics, each answered by the author; no other studies were found. The author of the 1997 article knew of no other published studies since that date, although he has other studies in progress.(5)

Information on the Internet was sparse. One Web site (6) was found that mentioned the test and the results of a clinical series: “We have tested thousands of people in the past five years and have found less than 1% have normal sized blind spot maps.” No further details or documentation were provided. This Web site advertised a device for chiropractic manipulation (an activator) and was riddled with errors (such as confusing the blind spot in the eye with a driver’s blind spot). On a second Web site, (7) a chiropractor criticized Dr. Carrick for dogmatism and failing to respond to criticism about the 1997 study and criticized a third, now-defunct Web site on which a chiropractor had made statements about the blind spot not supported by anything in Dr. Carrick’s study or in the rest of the chiropractic literature. Anecdotal evidence was found indicating that a number of clinicians have also found enlarged blind spots with the test, and that the information has been clinically useful.

In the absence of any other information suitable for analysis, this analysis is based solely on the one published article.

RESULTS

Summary of the Study

The objective was “to ascertain whether manipulation of the cervical spine is associated with changes in brain function.” The subjects were 500 volunteers enrolled in postdoctoral neurology programs. Their blind spots were mapped with a simple paper-and-pencil test by 2 “blinded” examiners, and the 2 maps were judged for reproducibility by 2 “blinded” examiners who superimposed the 2 maps over a bright light. Four hundred seventy-three pairs of maps were judged reproducible; all had an enlarged blind spot on one side, with an average circumference of approximately 1.5 times the circumference of the smaller spot. In 330 subjects, the right blind spot was larger; in 143 subjects, the left one was larger. In 20 subjects with enlarged blind spots on the right, the second cervical motion segment was reduced on the right in 10 and on the left in 10. Retesting showed that after manipulation on the right side, the right blind spot was significantly smaller and the left blind spot was unchanged; after manipulation on the left side, the right blind spot was unchanged and the left blind spot was significantly larger. The remaining 453 patients were all manipulated on the same side as the enlarged blind spot; after manipulation, the enlarged blind spot was significantly smaller, while the blind spot in the other eye did not change. The study concluded:

Accurate reproducible maps of cortical (i.e. brain) responses can be used to measure the neurological consequences of spinal joint manipulation. Cervical manipulation activates specific neurological pathways. Manipulation of the cervical spine may be associated with an increase or a decrease in brain function depending upon the side of the manipulation and the cortical hemisphericity (i.e., side of decreased brain function) of a patient.

The study refers to the blind spot maps as “physiological cortical maps” and “an integer of brain activity.”

Description of the Blind-spot Test

Ophthalmologists have a variety of standardized methods for testing visual fields. The test in this study is a simple paper-and-pencil variant of the tangent-screen method:

  1. A piece of paper with a dot in the center is placed at eye level 28 cm from the subject’s forehead.
  2. The subject covers one eye and fixates on the dot with the other eye.
  3. The examiner moves a small target laterally from the dot to the edge of the paper; pencil marks are made where the target seems to disappear and where it seems to reappear.
  4. The target is placed in the area where it was invisible and moved up, down, and at 45° angles until a total of 8 dots have been mapped to delineate the borders of the blind spot.
  5. The 8 pencil marks are connected with straight lines and the circumference of the blind spot is measured.

Possible Methodological Flaws

  1. The test as described is imprecise and would be expected to vary with many factors such as degree of cooperation, speed of target movement, slight tilting of the head, reliability of fixation, judgment as to where to draw the dots, etc.
  2. The measurements of this new blind-spot mapping method were reproducible within the study but were not shown to be valid; there was no comparison with measurements by other, older methods.
  3. Reproducibility was determined by superimposing 2 drawings over a bright light; this was a subjective judgment. The maximum difference allowed between 2 “reproducible” maps was not quantified.
  4. The investigators may have been biased, as suggested by the objective of the study. (They were trying to study the effect of manipulation on brain function, not simply to establish a blind-spot-mapping test.)
  5. There were no controls who were not manipulated or who received sham manipulation or manipulation of levels below the second cervical vertebra.
  6. The subjects were postgraduate chiropractic neurology students. They were presumably biased in favor of chiropractic and may have been biased towards finding expected results. They knew which side of their spine had been manipulated and therefore understood which eye would be expected to show a change.
  7. Although the examiners were taught to monitor the subject’s eye movements, it seems unlikely that they could watch the subject’s eyes and draw dots on the paper at the same time. The subject may have been able to glance surreptitiously at how the map was developing. The subject may have been able to compare the left map to the right.
  8. All 500 subjects had enlarged blind spots, but the study does not mention whether anyone had equal blind spots on initial testing and was not included in the study.

References Cited in the Study

The 47 references listed are mostly irrelevant or misinterpreted and do not support the findings and conclusions of the study. Reference 1 describes how the brain chooses what illusion to put in the blind spot when adjacent signals are ambiguous, i.e., where 2 color zones abut. Reference 2 is cited to support the statement, “Cortical receptive field size varies in different individuals.” It actually says there is a rapid variation in cortical receptive-field size in response to stabilized images in the same individual. Reference 3 says: “Ocular dominance stripes … are absent from the cortical representations of the blind spot and the monocular crescent” in the Cebus monkey. Reference 4 concerns possible mediation of contour interaction phenomenon by long-range connections within the striate cortex. From this, Dr. Carrick hypothesizes that “the frequency of firing of these cortical connections affects visual perception and enlargement of the blind spot might be attributable to any mechanism that decreases the firing rate of horizontal cortical connections, hence decreasing the probability of neuronal summation.” (1, p. 537) References 5-9 all describe retinal diseases (central-retinal vein occlusion, multiple evanescent white-dot syndrome, etc.) that may cause an apparent enlargement of the blind spot as well as other areas of loss of vision. References 10-12 refer to conditions that Dr. Carrick interprets as unexplained blind-spot enlargement but actually are known to be due to retinal disease, such as acute zonal occult outer retinopathy (AZOOR). Reference 13 shows that microwave radiation can alter the size of the blind spot (by damaging tissue). Reference 14 shows that treatment of glaucoma can reduce an enlarged blind spot caused by local pressure due to glaucoma. Reference 15 shows that glaucoma can damage the retina near the blind spot. Reference 16 states that multiple events affecting vision are often related. (It reports a case of chorioretinopathy complicated by occipital lobe infarction and sinusitis in a drug abuser.)

After citing these 16 references, Dr. Carrick concludes, “It is clear that the size and shape of the blind spot is a product of neuronal activity and that this activity can be affected by a variety of processes. It was therefore chosen as a sensitive integer of brain activity that could be used to measure changes in cortical activity if other integers were manipulated.” (1, p. 539) This conclusion is not justified.

References 17-23 refer to various methods of recording blind spots (such as computerized static perimetry and multifixation campimetry), pointing out that they are more expensive than the pencil-and-paper method.

The abstract of one of these references actually states: “Statistically there was no evident difference of the size and depth of the defects of the blind spot either between the right and left visual field or among the individual age groups” (8) — in direct antithesis to the findings of Dr. Carrick’s study.

References 24-43 consist of various studies relating to the thalamus, the optic nerve and its connections, the plasticity of the visual cortex, etc. These studies say nothing about any cortical effect on the size of the blind spot or about any cortical effect of neck manipulation. Dr. Carrick uses them as departure points for imaginative speculation about how nerve signals from the neck might possibly interact with optic-nerve signals through some mechanism which has never been recognized. For example, reference 27 is titled “In Vivo Demonstration of Altered Benzodiazepine Receptor Density in Patients with Generalized Epilepsy.” He cites this to support this statement: “The amplitude of somatosensory receptor potentials will influence the frequency of firing of cerebello-thalamocortical loops that have been shown to maintain a central integrative state of cortex.” He then speculates: “Changes in the amplitude of muscle stretch receptors and joint mechanoreceptors that dictate the frequency of firing of primary afferents that contribute to cerebellothalmocortical loops should also affect the integrative cortical state, which might affect the size of the blind spot when visual afferents are maintained in a steady state.” (1, p. 540) (Emphasis added.)

References 44-47 are Dr. Carrick’s own publications describing his manipulative techniques.

Logical Flaws

  1. Nothing in the paper or the references it cites justifies calling a blind-spot map “a physiological cortical map” or “an integer of brain activity.” The blind spot is a fixed anatomical feature. The brain functions to fill in the blind spot but has no effect on its size.
  2. When a new test contradicts the findings of all previous tests, its accuracy must be suspect. Either the blind spots are the same size or they are not. Either this study is wrong or all previous observers are wrong. The test cannot be used as a measurement tool in further experiments until this dilemma is resolved.
  3. Carrick’s argument boils down to this: spinal manipulation must affect cortical activity because it changes the size of the blind spot, and the blind spot must represent a map of cortical activity because its size changes with spinal manipulation. Demonstrating that the size of the blind spot changes following manipulation does not prove that manipulation changes the brain or that the brain changes the blind spot, even if no other explanation is apparent. The fact that A is followed by C does not prove that A causes B and B causes C. That amounts to what has been called a logical “sillygism.”

Other Observations

In Figure 8 of the paper, a heading reads: “Blind Spots Are the Consequence of Global Brain Activity and Representative of the Anatomical Size of the Optic Disc.” This is a false statement not justified by anything in the paper.

The language of the paper is often confused and unclear. It is difficult to understand what the author means by statements such as “A constant type of environmental stimulation (vision) was used in this research to stimulate the brain through specific known neuronal pathways. The effects of this environmental stimulation were used to affect human perceptual activity and demonstrate the effectiveness of cortical mapping through comparison.” (1, p. 531)

Neuroanatomists have mapped the nervous system in great detail, and pathways that might allow spinal manipulation to affect the brain are not known to exist.

The study describes detailed statistical analysis of manipulation experiments based on a blind-spot test that has not been shown to be valid. Statistical significance is meaningless if it is based on invalid data.

CONCLUSION

Evidence supporting the use of the blind-spot-mapping test is limited to one fatally flawed study. The evidence of this study that one blind spot is larger than the other is unconvincing and contradicts all previous findings. The assertion that the size of the blind spot can change is opposed to all present anatomical and physiological knowledge. There is no evidence that blind-spot mapping reflects cortical function or that manipulation can affect the size of the blind spot by stimulating cortical function. The study fails to meet its stated objective of ascertaining whether manipulation of the cervical spine is associated with changes in brain function. The conclusions it reaches are unjustified and illogical. The paper-and-pencil blind-spot-mapping test has not been validated, and there is no reason to think that it has any clinical usefulness.

REFERENCES

  1. Carrick F. 1997. Changes in brain function after manipulation of the cervical spine. J Manipulative Physiol Ther. 20(8): 529-545.
  2. Tacoma (Washington) News Tribune, December 31,2002.
  3. Palmer D. The Chiropractor: Whitefish, MT: Kessinger Publishing; 1997.
  4. Sportelli L. 2000. Introduction to Chiropractic. 10th ed. Norwalk, IA: Practicemakers Products.
  5. Author? 2002. Personal communication. December 26.
  6. Biokinetics Health Systems. Frequently Asked Questions. Available at: http://www.biokineticshealth.com/faqs. html. Accessed December 31,2002.
  7. Seaman D. Philosophy and science versus dogmatism in the practice of chiropractic. The Chiropractic Resource Organization. Available at: http://www.chiro.org/LINKS/ ABSTRACTS/Science _ vs_ dogmatism.shtml. Accessed December 31, 2002.
  8. Lest’ak J. 1993. [Marriotte’s spot]. Cesk Oftalmol 49(6):394-398.

Posted in: Chiropractic, Diagnostic tests & procedures, Neuroscience/Mental Health, Ophthalmology

Leave a Comment (64) ↓

64 thoughts on “Blind-Spot Mapping, Cortical Function, and Chiropractic Manipulation

  1. nobs says:

    HH claims:

    “…. In 2005 I published an article in The Scientific Review of Alternative Medicine (Vol 9, No 1, p. 11-15) entitled “Blind-Spot Mapping, Cortical Function, and Chiropractic Manipulation.” It was an analysis of a study Carrick had published.

    Carrick read a shorter, popularized version of my critique in Skeptical Inquirer and responded with a diatribe……. ”

    1- How could Carrick have read a “shorter, popularized version” of your 2005 op/ed piece in SRAM…… in 2004? His (in your words)”diatribe” specifically references to the Nov/Dec 2004 issue of Sceptical Inquirer.

    2- Is this the 1997 cite to which you refer to in your 2004 and 2005 op/eds, AND your above claim(s)?

    J Manipulative Physiol Ther. 1997 Oct;20(8):529-45.

    Changes in brain function after manipulation of the cervical spine.

    Carrick FR.

    Abstract

    OBJECTIVE:

    To ascertain whether manipulation of the cervical spine is associated with changes in brain function.

    DESIGN:

    Physiological cortical maps were used as an integer of brain activity before and after manipulation of the cervical spine in a large (500 subjects), double-blind controlled study.

    SETTING:

    Institutional clinic Participants: Adult volunteers.

    INTERVENTION:

    Five hundred subjects were divided into six comparative groups and underwent specific manipulation of the second cervical motion segment. Blinded examiners obtained reproducible pre- and postmanipulative cortical maps, which were subjected to statistical analysis.

    MAIN OUTCOME MEASURES:

    Brain activity was demonstrated by reproducible circumferential measurements of cortical hemispheric blind-spot maps before and after manipulation of the second cervical motion segment. Twelve null hypotheses were developed. The critical alpha level was adjusted in accordance with Bonferroni’s theorem to .004 (.05 divided by 12) to reduce the likelihood of wrongly rejecting the null hypothesis (i.e., committing a Type I error).

    RESULTS:

    Manipulation of the cervical spine on the side of an enlarged cortical map is associated with increased contralateral cortical activity with strong statistical significance (p < .001). Manipulation of the cervical spine on the side opposite an enlarged cortical map is associated with decreased cortical activity with strong statistical significance (p < .001). Manipulation of the cervical spine was specific for changes in only one cortical hemisphere with strong statistical significance (p < .001).

    CONCLUSIONS:

    Accurate reproducible maps of cortical responses can be used to measure the neurological consequences of spinal joint manipulation. Cervical manipulation activates specific neurological pathways. Manipulation of the cervical spine may be associated with an increase or a decrease in brain function depending upon the side of the manipulation and the cortical hemisphericity of a patient.

    3- If it indeed is, Why do you fil to cite it? It is only appropriate to truthfully cite the article/abstract you are in fact critiquing, not a ficticious abstract you confabulated to intentionally mislead readers. If I am correct, it is very telling of your dogmatic biases leading to a very questionable willingness to misrepresent.

    4- This study generated many LTEs, however none of them were from you….?? Why? LTEs are the scholarly, science-based, path to rebut study findings/methods/other scientific concerns. HMMM….??

  2. WilliamLawrenceUtridge says:

    Nobs:

    Regards your first point, the shorter version may have preceded the longer. Hardly requires time travel to produce a quick analysis for a popular publication, followed by a lengthier one for a more scholarly audience.

    Regards your second and third, have a look in the section titled “references”. In particular, compare reference 1 to the one pasted into your comment.

    Regards your fourth, if I were guessing it would be because she responded to the paper seven years after it was published in an obscure chiropractic journal. Chances are, in the substantially pre-internet age, you can’t submit a letter to the editor seven years after the fact.

  3. nobs says:

    # WilliamLawrenceUtridgeon 29 Nov 2011 at 9:25 am

    “Nobs:

    “Regards your first point, the shorter version may have preceded the longer. Hardly requires time travel to produce a quick analysis for a popular publication, followed by a lengthier one for a more scholarly audience.”

    Neither publication HH cites is “scholarly”. Skeptical Inquirer? SRAM ? Sram is not pub med indexed…never has been, never was. In fact it was rejected for indexing 4 times. Further more, the Hall/Carrick exchange of 2004, was pre-Sram publication, although she implied/intentionally misled readers to assume it as ‘post-Sram’ in the blog above.

    “Regards your fourth, if I were guessing it would be because she responded to the paper seven years after it was published in an obscure chiropractic journal. Chances are, in the substantially pre-internet age, you can’t submit a letter to the editor seven years after the fact.”

    1- I dispute your assertion of JMPT as an “obscure chiropractic journal”. It is a peer-reviewed, pubMed indexed journal (has been for decades) and a premier journal in manual medicine…….something that cannot be said for either “Skeptical Inquirer” or “SRAM”.

    2- I also dispute your assertion of 1997 as “substantially pre-internet age”. C’mon. Seriously.

    Either way- HH fails on several counts, before even getting to her “critique”…..primary being failure to cite the publication/study of her “critique”. A big OOOOPS in science-based exchanges. Pretty fundamental and essential stuff. When an op/ed begins with such fundamental flaws and misrepresentations,(as I noted above) it is impossible to consider any susequent….”critiques” valid, because the fundamental claim is corrupted.

  4. WilliamLawrenceUtridge says:

    Actually, you’ve managed to hyperfocus on a small number of nit-picks and non-errors. For instance, your points 2 and 3 were flat-out wrong and you’re criticizing Dr. Hall for not writing a letter to the editor seven years after the publication of the article. You’re also completely avoided the main thrust of this post – there’s no reason to believe manipulating the cervical vertebrae would alter the size of the blind spot; the test used hasn’t been validated; there’s no reason to think the blind spot “maps” the brain; and most importantly, Carrick’s paper in no way justifies the use of “chiropractic neurology” in general or this test specifically.

    Claiming Dr. Hall “failed” before getting to her critique seems like little more than a handwaving excuse to ignore her critique. The flaws you’re pointing to aren’t “fundamental”, they’re either minor chronological disputes or other trivialities. Rather than picking at dates and scholarly-ness of publications, why don’t you engage with the substance? For instance, do you believe that adjusting the cervical vertebrae would alter the size of the blind spot in the eye? Why? Do you believe that the blind spot itself somehow “maps” the brain? Why? What do you think of the sources used by Carrick and do you think they substantiate the points he makes?

    Your claims of “flaws” are like me dismissing your posts due to spelling errors. You’re ignoring the substance and instead assuming and projecting malice on a fairly basic critique of a fringe idea being used to promote a fringe treatment. That’s a pretty good reason to dismiss your comments as bad-faith grousing rather than take them seriously.

  5. Janet Camp says:

    @Nobs

    Pathetic.

  6. Harriet Hall says:

    @nobs,

    Wow! Your comments astound me. And they are distractions rather than responses to the content of my criticism of Carrick’s study.

    1. The SRAM article was written months before the SI article but took longer to appear in print.
    2. Yes, that is the abstract of Carrick’s JMPT article.
    3.I DID NOT fail to cite it. See footnote 1.
    I DID NOT “confabulate a fictitious abstract to intentionally mislead readers.” That accusation is offensive. In fact, I did not present an abstract at all. If you think I misrepresented Carrick’s article in any way, please explain with facts, not insults.
    4. Since it was many years after the fact, the editors of JMPT would not have published a letter to the editor. Even so, I seriously considered writing the editors to chastise them for an editorial policy that allowed the publication of such a substandard article. I decided it would likely be a waste of my time, so I didn’t. By the way, a couple of the published letters raised concerns similar to mine and Carrick’s responses to them showed that he failed to even understand them.

    SRAM was a peer-reviewed journal of considerably higher quality than many of the PubMed listed CAM journals. It was repeatedly rejected for PubMed listing because CAM advocates on the committee voted against it. Wally Sampson could tell that story. My SRAM article was not an “op-ed” piece, but a peer-reviewed study of “blind spot” claims.

    Do you believe almost everyone has a blind spot 50% larger in one eye than the other?
    Is there any evidence outside of this one study that neck manipulation changes the size of the blind spot?
    Do you know what an “integer of brain function” means?
    Do you think Carrick’s study shows that manipulation is associated with changes in cortical function?
    What is your agenda here?

  7. DevoutCatalyst says:

    “Do you know what an “integer of brain function” means?”

    That Jethro Bodine is being quoted?

  8. WilliamLawrenceUtridge says:

    Wow.

    I’m reading Dr. Carrick’s response to Dr. Hall (here) and it’s quite the thing. He defends his use of manual rather than machine-based teste because the machines are expensive (?) but manual is the gold standard (I’d love to hear what an opthamologist says about that). He goes on to state:

    Hall would have the reader believe that my study is the only study which links manipulation to visual system…The limited references at the end of her article would clearly demonstrate Hall’s lack of ability to search the literature and recognize the vast array of information on this topic literally exploding in the referenced journals. Ocular symptoms in cervical (neck) osteochondrosis has been discussed in the literature (5) as has the treatment of the loss of vision caused by cervical spondylosis utilizing combined traditional Chinese and western medicine approaches (6). Changes in the organ of vision has been described in cervical osteochondrosis (7) and the identification of cervical visual disturbances and its manipulative treatment is appreciated (8).

    References 5-8 are, and I’m not kidding:

    5 ) Krylova LM, Klocheva EG. [Ocular symptoms in cervical osteochondrosis and vegetative disorders]. Vestn Oftalmol 1978(6):25-7.
    6 ) Zhang CJ. [Treatment of loss of vision caused by cervical spondylosis with combined traditional Chinese and western medicine: report of 4 cases (author's transl)]. Zhonghua Wai Ke Za Zhi 1979;17(6):437-8.
    7 ) Lysenko TA, Kuz’mina AP, Kolesnikova MA. [Changes in the organ of vision in cervical osteochondrosis]. Oftalmol Zh 1980;35(5):298-9.
    8 ) Zhang CJ, Wang Y, Lu WQ, et al. Study on cervical visual disturbance and its manipulative treatment. J Tradit Chin Med 1984;4(3):205-10.

    Apparently the vast array of information on this topic literally exploding in the referenced journals consists of four articles (one of which is only 4 cases), two in Russian, one published in the J. of TCM, the latest being from 1984. There’s also a weird mingling of “tunnel vision” with the apparent topic of blind spots (though perhaps that’s my ignorance, I’m not an opthamologist, not even sure if I can spell it properly). He also cites a lot of work by a guy named Gorman, who’s fond of case studies. Seriously, Carrick claims spinal manipulation can fix X, Y and Z eye problems, and each example appears to be a reference to one of Gorman’s case studies.

    A bit later on there’s a claim that a guy in England (N. Daubeny) replicated his work. Could be true, but apparently it wasn’t published.

    And indeed, he does call her psychotic. Twice. Seems a charming fellow.

  9. cervantes says:

    It’s pretty obvious who has an abnormally large blind spot here, and it ain’t Dr. Hall.

  10. ConspicuousCarl says:

    “nobs” apparently thinks that abridged articles are constructed by grabbing the original off of a magazine rack and going at it with scissors. Obviously the full version would have to be printed first.

    Carrick’s theory is nutty anyway. He is focusing so intensely on the exact nature of an individual’s blind spot as if its partial filling-in somehow represents a neurological stress test on the brain’s aptitude. The whole point of the blind spot’s location is to be off to the side where visual input is not given detailed analysis anyway.

    Even in the rest of the off-centered area of vision, where there ISN’T an optic nerve blind spot, the incoming data is horribly weak and vague. Our normal inability to notice our blind spot, as well as our inability to notice unusual things all over the peripheral area, is not because our mighty brains are filling it in with some photo-shopped raster based on intense analysis, but because our brains gleefully accept weak and incomplete data for peripheral areas and fill it in with vague casual assumptions about what we already think is there.

  11. DrRobert says:

    As a medical doctor who has a deep understanding and background in anatomy and physiology, I find the “science” and “anatomy” used by the chiropractor in this study appaling.

    Honestly, this study read like a high school science project. The subjects are his students. They’ve all built their career around psuedoscience. Absolute insanity.

    “Ok guys, now in this study where we chiropractors are trying to invent new neuro-anatomical pathways, and are attempting to legitimize ‘chiropractic neurology’, which your future career depends on, let me know if this blind spot gets smaller after I fool around with your neck. P.S. I hope you don’t die from vertebral artery dissection.”

  12. Harriet Hall says:

    @nobs,
    One more thing:
    “the Hall/Carrick exchange of 2004, was pre-Sram publication, although she implied/intentionally misled readers to assume it as ‘post-Sram’ in the blog above.”

    I didn’t imply that it was post-SRAM, and anyway, the timing is really irrelevant. When I first started looking into the subject I e-mailed him with questions and I brought up the major points later addressed in my SRAM article. I gave him a chance to explain himself further and he was unable or unwilling to do so.

  13. windriven says:

    “Ophthalmologists routinely map the blind spots when testing visual fields for clinical diagnosis and follow-up. Until 1997, no one had observed any significant difference in blind-spot size between the left and right eyes in the absence of retinal disease.”

    Are there any published data supporting the similarity of bilateral blind spots in the absence of retinal disease or should this statement be taken to mean that ophthalmologists only map blind spots when retinal disease is certain or suspected?

    Are the methods used by ophthalmologists to measure blind-spot size the same or different from the method used by Carrick?

    It would seem that an appropriately rigorous double blinded study protocol could have been used. One immediately wonders why it wasn’t. Testers could have been rotated so that no tester saw the same subject twice. Baseline tests could have been followed by subjects being separated into subsets where left side manipulation, right side manipulation, and some placebo manipulation, say temple massage were performed and each “intervention” followed by a retest. Lots of testers and lots of manipulators ;-) it is true. But then no one ever said science was easy.

  14. Harriet Hall says:

    @windriven,
    “should this statement be taken to mean that ophthalmologists only map blind spots when retinal disease is certain or suspected?”
    No, it should be taken to mean that there are no published observations by neurologists, anatomists, ophthalmologists or anyone else to indicate that one blind spot is larger than the other in persons without retinal disease. In fact, one of Carrick’s’ own references states they are equal in the two eyes. In his diatribe he tried to pass this off by questioning what “equal” meant, but I don’t think anyone would interpret a 50% difference in circumference as “equal.” If Carrick’s findings were accurate, and almost everyone had a blind spot that averaged half again as large in one eye, I find it difficult to believe that all previous observers had missed this. And if all previous observers had missed it, Carrick should have realized he had made a new discovery and should have tried to verify it so it would be in medical textbooks by now and so other researchers could have tried to figure out what it meant. Carrick didn’t even bother to consult an ophthalmologist who could have looked at records of patients who turned out not to have retinal disease and verified whether their blind spot was half again as large on one side and whether it was twice as likely to be larger in the right eye as in Carrick’s study.

    “Are the methods used by ophthalmologists to measure blind-spot size the same or different from the method used by Carrick?”

    Ophthalmologists use instruments and automation rather than paper and pencil, but the process is essentially the same.

  15. windriven says:

    @Dr. Hall

    “Ophthalmologists use instruments and automation rather than paper and pencil, but the process is essentially the same.”

    But wouldn’t one assume that instruments and automation produce a result more consistent and less prone to bias than a manual process using paper and pencil?

  16. Harriet Hall says:

    “But wouldn’t one assume that instruments and automation produce a result more consistent and less prone to bias than a manual process using paper and pencil?”

    I would certainly think so! When I first started looking into this, I did some informal home experiments with family and friends and was impressed that various factors could influence results. The only advantage I can see to a paper and pencil test is that it’s inexpensive and anyone can do it anywhere. It would be a simple matter to compare it to the automated tests for consistency and accuracy, and one of my points was that Carrick should have done that to validate his test before he used it for before-and-after-manipulation studies.

  17. Lytrigian says:

    Nobs can’t get anything right, can he?

    I also dispute your assertion of 1997 as “substantially pre-internet age”. C’mon. Seriously.

    The Internet was fully opened to commercial traffic only in 1995. In 1997 it had 70 million users, about 1.7% of the world’s population at the time. In June, 2011 it had over 2.1 billion, representing more than 30% of the world’s population.

    Yes, 1997 was “substantially pre-Internet age.”

    Source: http://www.internetworldstats.com/emarketing.htm

  18. Harriet Hall says:

    @Lytrigian,

    Besides the fact that his objection was just another meaningless distraction. With or without the Internet, journals simply don’t publish letters to the editor about articles that appeared seven years earlier.

  19. Lytrigian says:

    To be sure. But it’s the only thing here I’m qualified to comment about.

  20. Quill says:

    Dr. Hall writes:

    Readers can judge for themselves whether my critique amounts to fraud and whether I am showing signs of psychosis, whether Carrick is a good scientist and whether his reply to my critique was appropriate.

    I can find no fraud; if psychosis is present it’s well disguised behind a veritable wall of logic, concise prose and careful scholarship; Carrick could be considered a good scientist in much the same way Danielle Steele is considered a high-brow heavyweight by some of her readers; and his reply, ironically enough, seems to be psychotic babblings of a fraudulent nature that are barely readable much less intelligible.

  21. jhawk says:

    @ Harriet Hall

    The following study has nothing to do with blind spot mapping but is measuring cortical SEP’s post SMT.

    http://www.ncbi.nlm.nih.gov/pubmed/20350670

  22. Harriet Hall says:

    @jhawk,

    I have no idea what that study means. Do you? Why are they doing calculations based on evoked potentials from median and ulnar nerves? What would be the significance of suppressing dual inputs compared to individual ones? What was the control intervention? They say “These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation treatment.” and yet the studies were done in patients who were not in pain. And I don’t think it has been established that neck pain and function are improved by spinal manipulation as compared to mobilization and appropriate controls. Does this amount to grasping at straws, to saying “Look, we demonstrated that something changed so that must validate chiropractic manipulation?” That’s the kind of thing Carrick was trying to do. Perhaps neurologist Steven Novella can shed some light on how these findings might be interpreted.

  23. WilliamLawrenceUtridge says:

    Jhawk, that’s at best a starting point. If this work was done a century ago, it’s final results after replication, validation, extension, and above all explanation might justify chiropractic adjustment. A general criticism of CAM, including chiropractic, is the development and charging for interventions before the science supports them (and the failure to abandon them if the science fails to support them). This is at best a preliminary study to generate a hypothesis; it certainly doesn’t justify chiropractic manipulation. Once you understand the anatomy, physiology, mechanism, implications, and have conducted clinical trials on this approach – that would be a good time to start charging money for it. Otherwise you’re just like that asshole charging money to re-inject people with their own piss under the fraudulent guise of faked clinical trials.

  24. kagogo says:

    I have nothing substantial to add to the discussion so I’ll just say this: Harriet, you are awesome!

  25. nybgrus says:

    WLU basically said what I was going to. I also have no idea what the study actually demonstrates. At least from what I can tell it is yet another chiro study that boils down to “we pull and stretch nerves and stuff happens.” Whether that stuff has any bearing on any state of human pathology is never addressed. The chiros seem quite content to say “see! stuff happened!” and then claim justification for the use of (and charging for) various interventions (which all seem to converge around neck cracking). What about a study with 3 inputs? Maybe 4? If you get up to 20, frequentist statistics tell us at least one of them will be significant. Then you can hang your hat on 8 input modulation. All sCAMsters love the p-value but absolutely hate Bayes.

  26. Late to the party, but I’m going to pile on here and add my opinion that nobs’ complaints about this article are either irrelevant, incorrect, or both. As a rebuttal, it is a very weak sauce indeed when all you do is sloppily nitpick at your target’s credibility and fail to address anything.

    Credibility is largely irrelevant anyway — as it always is. Ultimately, arguments must always stand on their own … regardless of who is making them. And nobs “arguments” aren’t even about blind-spot mapping, but about Harriet!

  27. jhawk says:

    @ Harriet Hall

    How I understand it is that spinal dysfunction increases afferent input to the CNS and SMT reduces this afferent input and therefore changes the way the CNS responds to subsequent input like SEP’s.

    The control intervention tool the person in lateral flexion, extension and rotation without a HVLA thrust. The purpose was to act as a control for changes in cutaneous, muscular and vestibular input that would occur with this movement.

    The study was done on recurrent neck pain patients of which at the time of study were not in pain. Pain is known to effect some of these SEP’s and they thought it would confound the results.

    @ Harriet Hall and WLU

    This study was not meant to show effectiveness of SMT, it is trying to figure out exactly what the mechanism of action of SMT is.

  28. Harriet Hall says:

    @jhawk,

    Musculoskeletal conditions produce pain. Pain is perceived by the brain. That perception is altered by any treatment including placebo. The study doesn’t tell us anything about afferent input from the musculoskeletal condition. It doesn’t document that the subjects had any abnormality at the time they were pain-free and were being studied. Using the control intervention implies that a HVLA thrust has some special efficacy and the rest of the SMT treatment is irrelevant: that is an unproven assumption.

    I think any conclusions based on this research are questionable, and I don’t see how it could help figure out the mechanism of action of SMT.

  29. Scott says:

    A point of constructive criticism. (Or at least, that’s how it’s intended.) With the amount of stress placed on the size of the blind spot normally being equal, e.g.

    When a new test contradicts the findings of all previous tests, its accuracy must be suspect. Either the blind spots are the same size or they are not. Either this study is wrong or all previous observers are wrong. The test cannot be used as a measurement tool in further experiments until this dilemma is resolved.

    I’d really want to see more than one citation for the proposition, and one that the text around the citation describes a a statement from the abstract at that:

    The abstract of one of these references actually states: “Statistically there was no evident difference of the size and depth of the defects of the blind spot either between the right and left visual field or among the individual age groups” (8)

    I don’t believe it’s proper to make such broad statements as “all previous tests” or “all previous observers are wrong” without a firmer foundation. (This is not to say that such statements are incorrect. My point is the more targeted one that you haven’t adequately supported them with evidence.)

    This admittedly doesn’t materially disturb the conclusions. Even if there were no prior evidence on the subject of blind spot size, that wouldn’t change the fact that a new test should be validated against the preexisting state of the art before relying upon it. (Especially when its findings are anatomically implausible wrt the size changing.) And it has no bearing on the other reasons to conclude Carrick’s findings were bogus (term chosen with deliberation). But I expected better scholarship.

  30. jhawk says:

    @ Harriet Hall

    “The study doesn’t tell us anything about afferent input from the musculoskeletal condition.” Not the point of the study but it does reference where this has been shown.

    “It doesn’t document that the subjects had any abnormality at the time they were pain-free and were being studied.” The subjects had recurrent neck. Yes they were not in pain at the time of SMT but they were only adjusted if they were found to have restricted ROM and tenderness to palpation (joint dysfunciton).

    “Using the control intervention implies that a HVLA thrust has some special efficacy and the rest of the SMT treatment is irrelevant: that is an unproven assumption.” I disagree. They were using the control to make sure that the measurements they obtained via SEP were not due soley to touch and movement. If the control had not been used then saying this result was only from placebo or we touched them and something happened could have been possible.

    “I think any conclusions based on this research are questionable, and I don’t see how it could help figure out the mechanism of action of SMT.” This study tested the hypothesis that SMT alters cortical processing and sensorimotor integration. From the article “These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment.”

  31. Harriet Hall says:

    @Scott,

    I don’t think that’s a valid criticism. It is a general rule that all bilateral anatomical structures are equal on both sides. Anatomy textbooks don’t bother to specify that the left and right kneecaps are the same size, or the left and right iris, or the left and right eardrum. Bilateral equality is the default assumption. I would not expect it to be spelled out anywhere, and yet it was spelled out in a reference cited by Carrick himself! Carrick claims that one blind spot is half again the size of the other in almost every individual. It is up to him to prove his claim is true, not up to me to prove it is wrong. I couldn’t find any support for that claim elsewhere. I don’t know what evidence you think I should have provided.

  32. Harriet Hall says:

    @jhawk,
    “they were only adjusted if they were found to have restricted ROM and tenderness to palpation”
    Do all patients with previous episodes of neck pain have such findings? Were there subjects in the study who did not have such findings and were not adjusted but were dropped from the study? Had some or all of those patients been treated with SMT in the past? If so, why would they still have these abnormalities?

    The real question is: where is the evidence that the study subjects had increased afferent input?

    If neck manipulation changes integration of sensory input from the radial and ulnar nerves, does that mean it improves neck pain? Was the original cause of the neck pain even determined, or was it diagnosed as “joint dysfunction” by a chiropractor?

    I think using this study to justify manipulation amounts to grasping at straws.

  33. Cowy1 says:

    Can we compare the neck crack to massage or fellatio to see if those things also modify SEPs and therefore may influence a restoration of function following said intervention?

  34. WilliamLawrenceUtridge says:

    @Jhawk

    This study was not meant to show effectiveness of SMT, it is trying to figure out exactly what the mechanism of action of SMT is.

    Your response assumes that SMT is effective rather than that it needs to be tested. Further, this still places the cart before the horse – an intervention with known risks (including death) is being offerred as treatment to millions of people on a daily basis despite not being tested.

  35. Harriet Hall says:

    Why so many comments about the way I wrote the article and other peripheral issues and so few about the article’s content? Nobs seems to have run away – perhaps to hide and lick his wounds so he can avoid responding here and try again on another thread in the future when he hopes we will have forgotten. Does anyone else want to respond to the questions I asked him:

    Do you believe almost everyone has a blind spot 50% larger in one eye than the other?
    Is there any evidence outside of this one study that neck manipulation changes the size of the blind spot?
    Do you know what an “integer of brain function” means?
    Do you think Carrick’s study shows that manipulation is associated with changes in cortical function?

  36. Scott says:

    @ Harriet

    And if you’d said that in the rebuttal, I’d have no problem with it at all. “Bilateral structures are normally symmetrical, this reference says they were similar in size, reports of drastically different sizes were not found in the literature, therefore the conclusion that one is normally 50% bigger is highly unexpected and requires much stronger evidence” would be adequately supported. Making specific statements about the findings of “all previous tests” goes well beyond that.

    Yes, burden is on him to prove his assertion that they’re drastically different… but burden is on you to prove your assertion that “all previous tests” have had a particular result. Such specific assertions should have been either supported or omitted, particularly since they were not necessary to your conclusions. If it was meant as a rhetorical device rather than being taken literally, I at least didn’t understand it that way (which I’ll grant could be plausibly interpreted as a failing on my comprehension).

    Does that clarify my point at all?

    Why so many comments about the way I wrote the article and other peripheral issues and so few about the article’s content?

    Perhaps because the core of the article’s content is sufficiently well argued and supported that there’s not much to say other than “yep, that about covers it?”

  37. Harriet Hall says:

    @Scott,

    OK, I see your point. If I had had the advantage of your editorial input back in 2004 when I wrote the article, I would have changed the wording as you suggest. The article was one of the first things I ever published: I hope I have learned to state things more carefully since then.

  38. David Weinberg says:

    The simple statement that one eye has a larger blind spot than the other, without qualification, is meaningless. Despite the apparent symmetry, everyone has one leg that is longer than the other, or one ear slightly larger than the other, etc. There is also bound to be “noisy asymmetry based on random error in the measuring technique. there needs to be some predefined threshold degree of asymmetry which is meaningful, and outside the expected measuring error. It appears Dr Carrick never defined such a threshold. The paper states he studied 500 subjects with asymmetric blind spots, but doesn’t state how many patients he screened to find this cohort.

    Visual fields have been by clinicians for many decades. The methods have evolved from manual, to mechanical, to computerized. Todays visual field instruments monitor fixation, and give a reliability metric with each field. The technique used by Dr Carrick is a throwback to manual methods which were virtually abandoned by the time the paper was published. Even compared to the old manual tangent screens, Dr Carrick used a very idiosyncratic technique, so it is impossible to compare his numbers to any others.

    My first thought in reading Dr Hall’s review was that the asymmetry of the blind spot was due to imprecision of the technique, and the normalization after cervical manipulation was simple regression to the mean. I’m not sure this explains the magnitude of the effect he reported.

    How likely is it that Dr Carrick discovered a previously unrecognized degree of asymmetry in size of the physiologic blind spot. I haven’t found any other paper that specifically addresses this question (I am still looking). Even so, visual fields have been used clinically for decades. Vastly superior measuring techniques are routinely used. Visual fields have been used as endpoints in multiple large clinical trials. In clinical use, visual fields are almost always ordered in pairs eyes. One of the reasons that both eyes are evaluated together is precisely because asymmetry is carefully scrutinized as a marker of pathology. Given the collective experience with visual fields, it is quite implausible that this research detected a real, but heretofore undescribed asymmetry in healthy, asymptomatic graduate students.

    I was particularly amused by the quote Dr Hall found on the internet:

    “We have tested thousands of people in the past five years and have found less than 1% have normal sized blind spot maps.”

    Given that statement, either your method is flawed, or normal needs to be redefined. If 99% of people have abnormal blind spot maps, does that make them all candidates for cervical manipulation?

  39. If 99% of people have abnormal blind spot maps, does that make them all candidates for cervical manipulation?

    Well played, sir!

  40. gbove says:

    To add to this, I was involved in the review of the Carrick’s 1997 paper, and have no idea how it got past the reviewers or editors. As a chiropractor and scientist (and on the editorial board of that journal) I found it infuriating. There is no science involved in this “project.” I am not sure if Dr. Carrick earned a PhD, there is no information available. But as to his having a practice, he is not licensed as a chiropractor in Florida, or any other state, and wrote in 2007 “I work in the area of brain science and I have not maintained a physical practice of chiropractic for about 20 years.” Lots of deception, lots of weaving unrelated facts with ideas to make illogical conclusions that are very alluring to his followers.

  41. Harriet Hall says:

    If I remember correctly, David Epstein, the journalist who wrote about Carrick in Sports Illustrated, told me on the phone that he was able to verify that Carrick does hold a license in at least one state. And I believe he does have PhD, although it is in Education. Of course, the question of whether he is in practice is irrelevant to the question of whether his research makes sense.

  42. jhawk says:

    @ Harriet Hall

    In the article that we are all responding to you said: ” Neuroanatomy, as it is presently understood, tells us that spinal manipulation should not affect the brain or other structures within the skull; chiropractors believe it does, and they have been seeking scientific proof of that belief for over a century. The 1997 study by Dr. Carrick is considered by some to constitute that proof. The issue is an important one: if manipulation is proven to have an effect on brain function, there will be reason to accept chiropractic as a part of mainstream medicine and to teach it in medical schools.”

    The study I posted directly contradicts the first part of your statement ( “Neuroanatomy, as it is presently understood, tells us that spinal manipulation should not affect the brain or other structures within the skull.”)

    “Do all patients with previous episodes of neck pain have such findings?” No

    “Were there subjects in the study who did not have such findings and were not adjusted but were dropped from the study?” They took the first twelve they found with these findings and did not include or put others in control group. I don’t mean to be rude but have you read the full text as most of your questions are stated quite clearly in the article?

    “Had some or all of those patients been treated with SMT in the past?” Unknown and is not relevant to this study.

    “The real question is: where is the evidence that the study subjects had increased afferent input?”

    This question is a red herring. Again, you stated SMT does not affect the brain or structuress within the skull. This study says otherwise.

    “If neck manipulation changes integration of sensory input from the radial and ulnar nerves, does that mean it improves neck pain?” yes.

    “Was the original cause of the neck pain even determined, or was it diagnosed as “joint dysfunction” by a chiropractor?” Once again it is chronic reccurent neck pain of which is most likely a multicausal condition.

    “I think using this study to justify manipulation amounts to grasping at straws.”

    This study does not justify using SMT and was not intended to justify using SMT. Once again, it is trying to elucidate the mechanism behind SMT. From the article, “Significance: This study suggests that cervical spine manipulation may alter cortical somatosensory processing and sensorimotor integration.
    These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment”

  43. Harriet Hall says:

    @jhawk,

    No, I don’t have access to the full article. If you can send me an electronic copy, I’ll be happy to read it.

    It is a truism that everything that happens to the body has some effect on the brain. The question is whether there is an anatomic pathway from the spine to the brain that allows specific effects and whether SMT has any specific effects beyond those occurring with other forms of stimulation. Answering that question will require properly controlled studies comparing SMT to placebo interventions. An analogy is acupuncture, where brain imaging has shown increased production of endogenous opioids with acupuncture, but the same increase is observed when patients take placebo pills. In dogs, the same response is seen when you throw a stick for a dog to fetch. Finding a phenomenon that occurs with SMT doesn’t mean that SMT is the only thing that can produce that phenomenon, and it doesn’t mean that SMT is uniquely therapeutic.

    The conclusion of the study assumes that SMT offers effective relief of pain and restoration of functional ability. That has not been established to the satisfaction of the scientific medical community, so it seems premature to try to explain it.

  44. jhawk says:

    @ Harriet Hall

    “The question is whether there is an anatomic pathway from the spine to the brain that allows specific effects and whether SMT has any specific effects beyond those occurring with other forms of stimulation.”

    We now know (at least better than before) according to this study that SMT has speficic effects beyond passive head movement to SMT set up position, beyond a practicioners touch of cutaneous and MSK structures and beyond vestibular input to this movement. Is this response beyond that of massage or mobilization? To my knowledge this is still unkown.

    “The conclusion of the study assumes that SMT offers effective relief of pain and restoration of functional ability. That has not been established to the satisfaction of the scientific medical community, so it seems premature to try to explain it.”

    I am not sure I understand your comment as there are many basic science/moa studies that later lead into clinical effectiveness trials (eg. drugs).

    I can send you an electronic copy if you would like. Interestingly, it looks as though almost the exact same study was done in 2007 and printed in the journal of clinical neurophysiology. http://www.ncbi.nlm.nih.gov/pubmed/17137836. I found this one with full text online with a quick google search. Not sure if I can post here due to copyright laws?

  45. Harriet Hall says:

    @jhawk,

    “Is this response beyond that of massage or mobilization? To my knowledge this is still unkown.”
    My point exactly.

    “there are many basic science/moa studies that later lead into clinical effectiveness trials.”
    It’s legitimate to investigate basic science, and it’s legitimate to try to figure out “if” something works. Assuming something works and then trying to elucidate the mechanism by which it works amounts to fairy tale science.

  46. jhawk says:

    @ Harriet Hall

    “My point exactly.”

    Focus on the negative if you will but this study was in no way designed to even test these possible negatives. Maybe they will do a follow up with massage control except adjusting the thoracic spine since there is evidence for this (SMT to thoracic spine) for neck pain ( effectiveness of manual therapies, UK evidence report). Which I might add came out after this article. I, on the other hand, find it interesting to see in a basic science study that SMT has speficic effects beyond passive head movement to SMT set up position, beyond a practicioners touch of cutaneous and MSK structures and beyond vestibular input to this movement.

    “It’s legitimate to investigate basic science, and it’s legitimate to try to figure out “if” something works. Assuming something works and then trying to elucidate the mechanism by which it works amounts to fairy tale science.’

    I disagree. Most hypotheses are based on previous observations and testing these observations does not mean you are assuming it will work. Furthermore, even if you are assuming it would work it would not matter if the study is done correctly. Example 1: chiros have the clinical observation that LBP patients improve after SMT then chiro profession and others test this hypothesis in a RCT for effectiveness and also basic science research for moa. Example 2: ortho surgeons have clinical observation that debridement and lavage for OA of knee has good outcomes then test this hypotheses in RCT for effectiveness.

  47. nybgrus says:

    couldn’t help but jump in here:

    Focus on the negative if you will but this study was in no way designed to even test these possible negatives

    It’s not focusing on the negative. It is just not grasping at straws to claim some sort of justification. And don’t try and claim that isn’t what you are doing. You are currently using SMT and claiming specific effects for it to your patients. Hence all these basic sciences studies are indeed grasping at straws trying to work backwards – aka bad science.

    I, on the other hand, find it interesting to see in a basic science study that SMT has speficic effects beyond passive head movement to SMT set up position, beyond a practicioners touch of cutaneous and MSK structures and beyond vestibular input to this movement.

    Of course you do. You have a therapy that you are currently charging people for to prove works. We find it very uninteresting. Why? Because of course there is going to be some kind of effect by jerking on a nerve. I could punch you in the neck and it would have “specific effects beyond passive head movement to SMT set up position” and “beyond practitioners touch.” That tells us nothing useful about SMT nor punching people in the neck. All it tells us is that when you deform a nerve stuff happens. We already knew that. And it in no way applies to or justifies any specific chiropractic intervention.

    You see, good science would find this effect and they ask, “Hmm… I wonder what we can do with this effect?” and then come up with testable hypotheses and work from there. The reason chiropractic is bad science is because you take SMT as already being validated and say, “Hmm… maybe this is how SMT works!” That is working backwards from a conclusion and that is precisely the definition of bad science. You can always find evidence to fit any conclusion you may have. You wonder why I keep referring to creationists? That is why. They have all sorts of “evidence” to support the “fact” that the earth is 6,000 years old and they keep doing studies to prove that. It is completely analagous to using these sorts of studies to justify the use of SMT.

    I disagree. Most hypotheses are based on previous observations and testing these observations does not mean you are assuming it will work.

    This is true. But you aren’t applying this to SMT or chiro in general. You are assuming SMT works – because you are using it on patients!. No good data shows SMT works well for anything beyond chronic LBP and perhaps a couple of other indications of the same ilk. Besides the fact that sham acupuncture works just as well, have you refrained from using SMT for anything besides those indications? I sincerely doubt it. You believe SMT works despite either a lack of evidence or evidence against such a claim. You then take studies and try and demonstrate some sort of putative effect from pulling on a nerve and claim that explains how SMT works…. without actually establishing it works in the first place! Hence, bad science.

    Example 1: chiros have the clinical observation that LBP patients improve after SMT then chiro profession and others test this hypothesis in a RCT for effectiveness and also basic science research for moa

    Yes, and the data shows it works no better than sham acupuncture. There is also a pile of data demonstrating how and why that may be. So what further work are you doing to try and justify a massage mixed in with copious placebo?

    Example 2: ortho surgeons have clinical observation that debridement and lavage for OA of knee has good outcomes then test this hypotheses in RCT for effectiveness.

    Yes. And the data showed that it actually didnt really improve outcomes and in most cases worked no better than placebo interventions – much like SMT for LBP. The key difference is that unlike chiro, we then stopped doing debridement and lavage for knee OA. Those that still do it would be the same people criticized on this very forum. Have chiros abandoned SMT yet?

  48. Scott says:

    Put another way, there are two good justifications for doing basic science on such a subject.

    1. You want to find out to what use the science may be put. In this case, there is no treatment yet; one may be developed based on what the basic science shows. Since there is a specific treatment established, chiropractic is not in this situation.

    2. You have good evidence that a treatment works beyond placebo, and want to understand why it does. Chiropractic is similarly not in this situation since there is no good evidence that it works.

    You have to either abandon SMT (in favor of adopting whatever the science ends up saying works), OR produce good evidence that it works. Can’t do meaningful basic science (or accurately call yourself anything but a quack) until one of those conditions is met.

  49. nybgrus says:

    @Scott:

    Very succinct and accurate. Thanks.

  50. jhawk says:

    @nybgrus

    “It’s not focusing on the negative. It is just not grasping at straws to claim some sort of justification. And don’t try and claim that isn’t what you are doing. You are currently using SMT and claiming specific effects for it to your patients. Hence all these basic sciences studies are indeed grasping at straws trying to work backwards – aka bad science.”

    You could not be more wrong here. So, I will claim that is not what I was doing. Neither me nor this study is claiming justification for SMT. They are simply looking into a mechanism of action. I would never tell this moa to a patient as it is still only basic science and preliminary as I menitoned previously.

    The only reason I posted this study is becuase HH said this in her article “Neuroanatomy, as it is presently understood, tells us that spinal manipulation should not affect the brain or other structures within the skull”
    This statement is false and needs to be revised.

    If I wanted to show effectiveness for manual therapy I would have posted this study, http://www.ncbi.nlm.nih.gov/pubmed/20184717

    “This is true. But you aren’t applying this to SMT or chiro in general. You are assuming SMT works – because you are using it on patients!. No good data shows SMT works well for anything beyond chronic LBP and perhaps a couple of other indications of the same ilk.”

    No assumption, see above study. From the article “conclusion: Spinal manipulation/mobilization is effective in adults for acute, subacute, and chronic low back pain; for
    migraine and cervicogenic headache; cervicogenic dizziness; and a number of upper and lower extremity joint
    conditions. Thoracic spinal manipulation/mobilization is effective for acute/subacute neck pain, and, when combined with exercise, cervical spinal/manipulation is effective for acute whiplash-associated disorders and for chronic neck pain.” So we are not assuming it works the best evidence today says it works.

    “Besides the fact that sham acupuncture works just as well, have you refrained from using SMT for anything besides those indications? I sincerely doubt it.”

    I use SMT for above conditions and when a patient has exhausted all other options with no success and agrees to a trial treatment.

    “You believe SMT works despite either a lack of evidence or evidence against such a claim. You then take studies and try and demonstrate some sort of putative effect from pulling on a nerve and claim that explains how SMT works…. without actually establishing it works in the first place! Hence, bad science.”

    see above study (shows effectiveness of SMT) and above comment (study not used as effectiveness it is a basic science study and does not show effectiveness)

  51. jhawk says:

    my comment has been awaiting moderation since 4:46 yesterday so I will try and re-post.

    @nybgrus

    “It’s not focusing on the negative. It is just not grasping at straws to claim some sort of justification. And don’t try and claim that isn’t what you are doing. You are currently using SMT and claiming specific effects for it to your patients. Hence all these basic sciences studies are indeed grasping at straws trying to work backwards – aka bad science.”

    You could not be more wrong here. So, I will claim that is not what I was doing. Neither me nor this study is claiming justification for SMT. They are simply looking into a mechanism of action. I would never tell this moa to a patient as it is still only basic science and preliminary as I menitoned previously.

    The only reason I posted this study is becuase HH said this in her article “Neuroanatomy, as it is presently understood, tells us that spinal manipulation should not affect the brain or other structures within the skull”
    This statement is false and needs to be revised.

    If I wanted to show effectiveness for manual therapy I would have posted this study, http://www.ncbi.nlm.nih.gov/pubmed/20184717

    “This is true. But you aren’t applying this to SMT or chiro in general. You are assuming SMT works – because you are using it on patients!. No good data shows SMT works well for anything beyond chronic LBP and perhaps a couple of other indications of the same ilk.”

    No assumption, see above study. From the article “conclusion: Spinal manipulation/mobilization is effective in adults for acute, subacute, and chronic low back pain; for
    migraine and cervicogenic headache; cervicogenic dizziness; and a number of upper and lower extremity joint
    conditions. Thoracic spinal manipulation/mobilization is effective for acute/subacute neck pain, and, when combined with exercise, cervical spinal/manipulation is effective for acute whiplash-associated disorders and for chronic neck pain.” So we are not assuming it works the best evidence today says it works.

    “Besides the fact that sham acupuncture works just as well, have you refrained from using SMT for anything besides those indications? I sincerely doubt it.”

    I use SMT for above conditions and when a patient has exhausted all other options with no success and agrees to a trial treatment.

    “You believe SMT works despite either a lack of evidence or evidence against such a claim. You then take studies and try and demonstrate some sort of putative effect from pulling on a nerve and claim that explains how SMT works…. without actually establishing it works in the first place! Hence, bad science.”

    see above study (shows effectiveness of SMT) and above comment (study not used as effectiveness it is a basic science study and does not show effectiveness)

  52. Cowy1 says:

    @jhawk

    Wow, a review article from a chiropracty journal that indicates that chiropractic works; what a stunner.

    I have yet to see a study done by chiropractors that does not, in some way, have positive results for chiropracty. If only real medicine had this kind of track record.

  53. jhawk says:

    @cowy1

    Yes, a systematic review of the majority of manual therapy RCT’s that have been done to date.

    “I have yet to see a study done by chiropractors that does not, in some way, have positive results for chiropracty”

    Did you read the review? From the abstract ” The evidence is inconclusive for cervical manipulation/mobilization alone for neck pain of any duration, and for manipulation/mobilization for mid back pain, sciatica, tension-type headache, coccydynia, temporomandibular joint disorders, fibromyalgia, premenstrual syndrome, and pneumonia in older adults. Spinal manipulation is not effective for asthma and dysmenorrhea when compared to sham manipulation, or for Stage 1 hypertension when added to an antihypertensive diet. In children, the evidence is inconclusive regarding the effectiveness for otitis media and enuresis, and it is not effective for infantile colic and asthma when compared to sham manipulation”

  54. Cowy1 says:

    @jhawk

    So chiropractors are going to stop manipulating patients with mid back pain, sciatica, tension-type headache, coccydynia, temporomandibular joint disorders, fibromyalgia, premenstrual syndrome, pneumonia, asthma and hypertension? The ICPA and ACA says otherwise (http://icpa4kids.org/Chiropractic-Research/) and under “Scope of Practice” towards the bottom (http://www.acatoday.org/level3_css.cfmT1ID=13&T2ID=61&T3ID=149).

    Check out the websites of some of the largest chiropracty schools:
    Life U: (http://www.life.edu/OurMission). “As long as the body is kept free of interferences”. Largest chiropractic school in the world sounds like the old-school subluxation is a core part of their educational process.
    Palmer: (http://www.palmer.edu/PhilosophyStatement/). “Central to the Palmer philosophy is the removal of impediments to health through the correction of subluxations, thus normalizing the nervous system and releasing the body’s optimal potential”. Again mentioning subluxation and it sure don’t sound like simple little joint dysfunction.

    These are pretty damning statements considering the numbers (probably a majority) of chiropractors have graduated from these two schools. The closest school chiropracty has to science-based is NUHS and they spend enormous amounts of time teaching their students rank quackery like homeopathy, acupuncture and naturopathy.

    I skimmed the abstract; why would I waste time reading a review? I’m interested in RCTs. Besides, it’s not like any of that is going to change any chiropractor’s practice. As evidenced by the above, there are literally no standards. A chiropractor can claim pretty much anything she wants and the schools/professional organizations/licensing boards couldn’t care less.

    I actually did read the article posted earlier (about how the neck crack made some changes on imaging studies) and was less-than-excited by it for the same reasons as nygbrus.

  55. nybgrus says:

    In the spirit of fariness, I will call out Cowy1 a bit for saying he is not interested in reviews but in RCTs. Reviews are extremely useful.

    However, this one is not. The methodology of a review is very important since when you are pooling data and staistics it becomes exponentially easier to introduce bias. And of course, the interpretation after that is always highly suspect.

    I do like that jhawk has now stated that this review is the “best evidence” that says SMT works. I didn’t even have to read the actual article to dissect and destroy it. The abstract says it. BTW jhawk – have you actually read the full text of the article? Or did you just browse the abstract and take away the single sentence that makes you feel all warm and fuzzy?

    Let me put the abstract up in full:

    Spinal manipulation/mobilization is effective in adults for: acute, subacute, and chronic low back pain; migraine and cervicogenic headache; cervicogenic dizziness; manipulation/mobilization is effective for several extremity joint conditions; and thoracic manipulation/mobilization is effective for acute/subacute neck pain. The evidence is inconclusive for cervical manipulation/mobilization alone for neck pain of any duration, and for manipulation/mobilization for mid back pain, sciatica, tension-type headache, coccydynia, temporomandibular joint disorders, fibromyalgia, premenstrual syndrome, and pneumonia in older adults. Spinal manipulation is not effective for asthma and dysmenorrhea when compared to sham manipulation, or for Stage 1 hypertension when added to an antihypertensive diet. In children, the evidence is inconclusive regarding the effectiveness for otitis media and enuresis, and it is not effective for infantile colic and asthma when compared to sham manipulation.Massage is effective in adults for chronic low back pain and chronic neck pain. The evidence is inconclusive for knee osteoarthritis, fibromyalgia, myofascial pain syndrome, migraine headache, and premenstrual syndrome. In children, the evidence is inconclusive for asthma and infantile colic.

    So basically, they find uquivocal resultsfor PMS and pneumonia in adults and OM and enuresis in kids. Lets think about what kind of slant that means when doing these reviews. If I were doing a review and wanted to demonstrate that chiropractic was an evidence and science based discipline (or at least trying to move that way) I would not include studies on PNA and enuresis. That is Palmer subluxation stuff.

    But here’s the kicker – they even state that for some odd reason, cervical manipulation alone doesn’t seem effective, but somehow combined with other stuff it is? And note that massage is also effective for the same indications!.

    In other words – the data is all over the place. Some stuff that we know is BS is called BS. Some is called “inconclusive” and some is called effective… but massage works too.

    So how is this any different than what I have been saying all along? It is massage combined with placebo effects working only on conditions that are particularly amenable to massage and placebo effects.

    I don’t have the time or desire to pick through this one in depth like I have in the past for articles. If someone else is, I’d be happy to read it. But I really don’t even need to get past the abstract to see the BS for what it is. Especially bearing in mind that the abstract is supposed be the shiniest and best presentation of the data and that is what they can muster.

    Sorry jhawk – you haven’t really mananaged to demonstrate much of anything. A very similar review can and has been written about homeopathy and acupuncture.

  56. pmoran says:

    Yes, the results described in that abstract make little sense. There is certainly no suggestion of any kind of “class action” as you might expect if SMT has the systemic or remote effects (beyond placebo) on the wide range of medical conditions that traditional chiropractic thinking requires.

    The language is troublesome. If the question being asked is “where, if at all, does SMT work better than placebo?” then why wouldn’t the opposite of “effective” be “not effective”? There would be no need to specify “not effective —- when compared to sham manipulation”.

    The finality of the pronouncements (“is effective”, “not effective” etc) suggests that the authors do not yet understand the uncertainties inherent in sham-controlled trials of procedural/theatrical methods in self-limiting, subjective, and placebo-responsive conditions. Experience suggests that such studies tend to give positive results by default (note that it is exceptional for Cochrane to do a systematic review of just about anything, no matter how implausible, without finding some studies with positive results). Negative studies should thus be given more weight, if large enough to detect clinically worthwhile overall results and not obviously warped in some way.

    If the authors did understand what their data meant, their language would be full of the tentativeness of normal scientific discourse i.e. ” the currently available evidence suggests that — “, “it is possible/probable/unlikely that —” (etc). There would also usually be a comment on the quality of the evidence.

    It is tempting to think that by pronouncing against some areas of common SMT use they are hoping to give other areas more credibility.

    I don’t think jhawk is necessarily himself standing by the results of that review. He does, however, seem to want to keep the options for this side of chiropractic open.

  57. Bogeymama says:

    Was just catching up on my reading, and stumbled across an article that sounded vaguely familiar….

    Looks like Carrick is getting tons of free publicity right now as the hero who “rebuilt Sidney Crosby’s brain” as the article is titled. It’s in Canada’s weekly newsmagazine Macleans (similar to Time), and reads like an uncritical advertisement for his services.

    http://www2.macleans.ca/2011/11/03/rebuilding-crosbys-brain/

    Can’t believe it’s the same guy you’re talking about here.

  58. jhawk says:

    @nybgrus

    “In the spirit of fariness, I will call out Cowy1 a bit for saying he is not interested in reviews but in RCTs. Reviews are extremely useful.”

    I appreciate the fairness here and agree with you that reviews can be a helpful way of limiting cherry picking.

    “I didn’t even have to read the actual article to dissect and destroy it. The abstract says it. BTW jhawk – have you actually read the full text of the article? Or did you just browse the abstract and take away the single sentence that makes you feel all warm and fuzzy?”

    Yes I have read the full article and would not post or dissect articles without reading the full text first.

    “Let me put the abstract up in full:” If you look at the comments above to you and cowy, I had already posted this full abstract. Effective results to you and ineffective results to cowy plus the link to the full abstract. I was not picking out single sentences.

    “So basically, they find uquivocal resultsfor PMS and pneumonia in adults and OM and enuresis in kids. Lets think about what kind of slant that means when doing these reviews. If I were doing a review and wanted to demonstrate that chiropractic was an evidence and science based discipline (or at least trying to move that way) I would not include studies on PNA and enuresis. That is Palmer subluxation stuff.”

    They were looking at all RCT manual therapy evidence and they found RCT’s for 26 conditions (13 MSK, 4 types chronic HA and 9 non-MSK). Not including the non-MSK would have been suspect. Furthermore, it adds to the argument that chiro’s should not be claiming to fix this stuff (which I believe was their intent after reading the full article)

    “But here’s the kicker – they even state that for some odd reason, cervical manipulation alone doesn’t seem effective, but somehow combined with other stuff it is? And note that massage is also effective for the same indications!”

    For chronic neck pain massage seems to be more effective than manipulation alone. For acute and subacute neck pain thoracic manipulation is more effective. Massage has moderately positive results for chronic LBP and SMT has highly postive results. SMT also has moderately positive results for acute LBP and massage does not. This is why you should read the full article.

  59. Bogeymama says:

    Didn’t mean to submit yet – there’s quite alot in there about Carrick’s background, including that he got his PhD from Walden, that it was “self-designed” and was in what he calls “brain-based learning”. It then goes on to say that around that time he began to bring comatose patients out of their vegetative states, and had a PBS program describe him as a “remarkable healer and teacher” in Waking up the Brain: Amazing Adjustments.

    The whole article is a massive stroking (sorry), presumably because he is a Canadian (!) who brought back Canada’s hockey hero to Canada’s favourite sport.

    Seriously, brain-based learning? That’s a good one. I wasn’t aware there was a type of learning that did not involve the brain.

  60. jhawk says:

    comment above @nybgrus is awaiting moderation

    @pmoran

    “There would also usually be a comment on the quality of the evidence.”

    I can’t imagine you read this review after making this comment as the quality of evidence is discussed all over the article.

    “The finality of the pronouncements (“is effective”, “not effective” etc) suggests that the authors do not yet understand the uncertainties inherent in sham-controlled trials of procedural/theatrical methods in self-limiting, subjective, and placebo-responsive conditions. Experience suggests that such studies tend to give positive results by default (note that it is exceptional for Cochrane to do a systematic review of just about anything, no matter how implausible, without finding some studies with positive results). Negative studies should thus be given more weight, if large enough to detect clinically worthwhile overall results and not obviously warped in some way.”

    I think you will find the discussion section interesting and that the authors are fully aware of these uncertainties.

  61. Cowy1 says:

    @ jhawk and nybgrus

    Fair enough, I probably should have read the review. My line of thinking was that, considering the generally poor quality of primary research, why read a review of it?

    Besides if, like anyone with a functioning brain could predict, SMT doesn’t work for non-MSK conditions will this change chiropractor’s practice patterns? I think not, for the reasons I listed above.

  62. nybgrus says:

    @cowy1:

    You are right, and it is a safe assumption to make. However, especially here, we shouldn’t be in the business of making such assumptions. At best it means we can in turn be written off and have a minor detail lorded over us (remember who we are dealing with) and at worst we could miss out on something geniunely useful.

    @jhawk:

    For chronic neck pain massage seems to be more effective than manipulation alone. For acute and subacute neck pain thoracic manipulation is more effective. Massage has moderately positive results for chronic LBP and SMT has highly postive results. SMT also has moderately positive results for acute LBP and massage does not. This is why you should read the full article.

    You do realize that all you are demonstrating is exactly what we would predict with our current assumptions and understanding of chiropractic, right? The lines of efficacy are drawn along the same lines as pathology that is particularly amenable to placebo, regression to the mean, and simple massage. Anything else is demonstrated to have no effects from chiro. And those effects that are there are always “moderate” or “statistically significant” but rarely clinically significant.

    My claim has never been that absolutely every scrap of chiro is BS. Simply that a very, very, small amount of it is actually useful and that the majority of it is placebo and massage. This article fully supports that assertion.

    Furthermore, as we here have demonstrated to such an extent that (no matter how many times I see it) believe there is a still a discussion about it, chiro training in general still utilizes treatments and therapies for which there is no evidence or evidence against. And those that are the minority, like yourself and NMS-DC, are undoubtedly guilty of some such activity, but at the very least are proferring treatment which is in no way unique or particularly useful and relies to a large extent on treating self-limiting pathology with a heap of placebo. In other words, in no way is that a support for the existence of a field called “chiropractic.”

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