What is good research? That’s a multibillion-dollar question, and while a litany of keyboard warriors across the world can argue “science” on social media platforms, the truth is that it is complicated, nuanced, and based in scepticism. That is, good science asks if something is relevant, reliable, repeatable, and ethical among other things. It builds on the work of those who have gone before and asks, “what are the limitations and biases of this study?” and looks to improve upon them.
Good research also involves being responsible for doing proper background on the topic and being critical in the case you are writing. There should be no cherry picking or biased reporting. Arguably, all research has inherent bias, but good researchers call that out in their limitation’s sections.
All this said, case reports can be hard. They have a critical role in the hierarchy of evidence, especially in chiropractic. But over the years, we have seen case reports released in which the bias against our profession has hardly been cloaked. Let’s call a spade a spade here: we are talking about chiropractic and cervical artery dissection. But a recent landmark court case and separate critical review on the topic are noteworthy. In both cases, the conclusion was this: again, there is no evidence of causation. And that is a win for chiropractic.
We are talking about both of them today, but let’s start with a review recently published in the Chiropractic Journal of Australia (1) addresses a case published in the New England Journal (2)
Cervical Artery Dissection (CAD) is a tear or separation of one of the layers of the artery walls of the neck, specifically the carotid and vertebral. CAD can refer to either internal cervical artery dissection, and vertebral artery dissection (VAD). Cases of CAD are rare, with VAD being the rarest type at an estimated incidence of 1 case per 100,000 people each year.
Most cases of CAD are spontaneous with no obvious cause, but some cases of VAD have been reported following minor activities. These minor activities have included sports such as swimming, tennis, golf, karate, and even after some daily activities such as painting and going to the hairdresser or dentist.
CAD is also not just an illness for the unhealthy or elderly, spontaneous cases of CAD have occurred in healthy and young (<45) individuals.
Stroke is a risk for people with CAD, but seems to occur in a small proportion of all CAD cases, with CAD accounting for only 2% of all ischemic strokes. While CAD is not often attributed as the cause of strokes, in stroke patients under 45 years of age, spontaneous CAD accounts for an estimated 25% of strokes. (3)
The rarity and common spontaneity of CAD would usually make it difficult to propose a cause-and-effect relationship between its occurrence and a particular activity, however case reports associating CAD with spinal manipulative therapy (SMT) are often published. Some of these published case reports utilise the term ‘Chiropractor’ for someone who was not qualified.
Overall, there has been a substantial back and forth in published literature surrounding the risk of CAD, both ICAD and VAD, following spinal manipulation. A theory based on damage to the vertebral artery occurring around the C2 level of the spine was the basis for VAD to be highlighted as a risk for chiropractic SMT. To add to that, case reports of ICAD following SMT have been published. Conversely, studies reporting minimal risk of CAD after chiropractic SMT have also been published.
To cut to the heart of the matter, the truth of the topic is this; a mechanism for CAD damage by SMT is not well understood and is thus difficult to prove. Additionally, many of the published cases have significant omissions and flaws, which limit the capacity for discussion and deliberation around this topic. To put it bluntly, such case reports have been used in a largely political debate around chiropractic. We are no stranger to such debates. But we are about research. That’s why this particular point of vindication is important.
The case reviewed
Published in 2021, the case details a 47-year-old male presenting to a hospital in the USA, with a headache, pain on the left side of the neck, numbness on the left side of the face, and dizziness. This was reported as a minor stroke. The case follows other previous case reports that attribute the cause of VAD with chiropractic care.
The author of the review states the clinical history included in the case report was ‘ambiguous in key areas including that this patient had experienced a prior similar episode that preceded the current episode. Lindsey et al. did not report important clinical details about the earlier episode (such as suspected trigger or diagnosed cause for the head/neck pain), which could be critical to determining whether this case was more likely spontaneous VAD, or due to a minor activity being the final event before the artery finally dissected.’
Reporting any activities prior to the onset of the initial episode is important for the case report, as many other published cases detail some minor activities prior to the onset of pain. The inclusion of important factors of clinical history could help clarify the relationship between the treatment and the associated adverse event. This would include timing, duration, and symptoms before, during, and after chiropractic care.
A key point raised by the author conducting the critical review of the case report was the potential for protopathic bias. The best way to explain protopathic bias is by using an example;
A person has an underlying and undiagnosed condition, an illness they aren’t yet aware of. This condition causes pain in both knees. In response to the pain, the person decides to start strengthening their knees by exercising at the gym. If the underlying condition were then to be diagnosed, it may be postulated that the exercises caused the illness. In actual fact, the unknown illness is causing the pain and the exercising was a response to the pain, but this can be hard to identify so is something all clinicians and researchers should be aware of.
In the reviewed case the risk of protopathic bias is present in the attribution of the development of VAD and the subsequent symptoms of neck pain to SMT. There is the potential, especially as there was a history of previous symptomatic episodes, that the patient was already experiencing neck pain caused by VAD, and as a result of the pain sought chiropractic care. Although it cannot be determined, the risk of bias is present and relevant questions should have been asked to elucidate the sequence of events.
It was later detailed in the case that the patient had a connective tissue disorder, Ehlers-Danlos syndrome (EDS). It is unclear from the review specifically which kind of EDS the patient had, as vascular EDS would be most relevant to arterial wall weakness and vascular disorders.
Nevertheless, a connective tissue disorder is a significant risk factor for VAD and strokes. Other significant risk factors for stroke were also included in the case report; smoking, alcohol and substance abuse, and Ibuprofen use. Ibuprofen is a well reported risk factor for stroke, and thus the affect, duration, and dosage of Ibuprofen is important information to include. The risk factors were not heavily commented on, and instead the cause of VAD and stroke was attributed to SMT.
Case reports are retrospective, and as such cannot comment on or determine causality. They are only able to identify an association, the nature of which relationship can be further investigated in future prospective and controlled experiments. Thus, the original case report cannot prove that SMT caused VAD or stroke, and it would be incorrect to conclude so.
Overall, the reviewing author found the case report omitted important clinical information that may have skewed the interpretation of the relationship between SMT and VAD. Additionally, the cases included limited information about the nature of the chiropractic involvement and little discussion of the various risk factors and multiple hospital presentations associated with the vascular events, and their lack of appropriate management.
No Scientific Evidence Demonstrates a Causal Relationship between neck manipulation and cervical artery dissection:
The publication of this critical review coincides with another historical even: a Dutch court issued a ruling this past February in which experts concluded that there exists no scientific evidence demonstrating a causal relationship between neck manipulation and the occurrence of a dissection. They also concluded that the medical facts in the case under review could not determine what caused the event in the patient. Notably, the Court ruled that “it has not been legally and convincingly proven.”*
This is not the first time the issue of chiropractic care has come under the microscope for CAD. Back in 2017, another study found “no evidence for causation” between the two .
It now seems that while chiropractic evidence for the benefits of chiropractic post stroke are advancing, so too is the confirmation that chiropractic care, when delivered by a skilled and qualified chiropractor who checks for contraindications, has not been found to cause CAD.
It’s an historical court ruling, and an important critical review as we move forward in an exciting time for chiropractic.
Notes: *These quotes have been taken from an English translation of a Dutch media release, appearing on the World Federation of Chiropractic’s Facebook page, 22 February 2022. 
- Tuchin P. A critical review of a published case report that incorrectly attributed chiropractic care as a cause of vertebral artery dissection (VAD). Chiropr. J. Aust. 2022. 49(1).
- Lindsay ME, Dudzinski DM, Yoon BC, et al. Case 30-2021: A 47-Year-Old Man with Recurrent Unilateral Head and Neck Pain. N Engl J Med. 2021. 385(14):1317-1325
- Campos-Herrera CR, Scaff M, Yamamoto FI, Conforto AB. Spontaneous cervical artery dissection: an update on clinical and diagnostic aspects. Arquivos de Neuro-Psiquiatria. 2008. 66:922–7.
- https://www.rechtspraak.nl/Organisatie-en-contact/Organisatie/Rechtbanken/Rechtbank-Noord-Holland/Nieuws/Paginas/Chiropractor-vrijgesproken-van-veroorzaken-zwaar-lichamelijk-letsel-tijdens-behandeling.aspx?fbclid=IwAR2y8JWYpgnPAug5aJoiHpAdZ1TsVGuK1OB4CfVLQiq1tEgxGNv5WoM4jTk, 21 February 2022
- Church E, Sieg E, Zalatimo O, Hussain N, Glantz M, Harbaugh R (2016) “Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation,” Penn State Neurosurgery Channel, http://www.cureus.com/articles/4155-systematic-review-and-meta-analysis-of-chiropractic-care-and-cervical-artery-dissection-no-evidence-for-causationretrieved 29 March 2017