Systematic Review of Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation

Many people are concerned about adjusting their necks, so we decided to discuss the 2016 systematic review by Church et al. At Chicago Spine and Sports, we believe that you, the patient, have the right to be informed about your treatment options and to receive the care that you choose. If you do not want to have your neck adjusted, we have many other options to treat your neck and help you recover.

Introduction

Neck pain is a prevalent issue, leading to millions of ambulatory care visits each year. Many individuals seek chiropractic care for relief, which often includes cervical spine manipulation. However, concerns have arisen about a possible link between chiropractic neck manipulation and cervical artery dissection (CAD), a rare but serious condition that can lead to stroke. A systematic review and meta-analysis conducted by Church et al. aimed to evaluate the evidence surrounding this potential association.

Background

Case reports and case-control studies have suggested an association between chiropractic manipulation and CAD, but no causal relationship has been firmly established. This systematic review and meta-analysis aimed to comprehensively evaluate the available evidence on this topic.

Methods

The research team conducted a thorough search using terms like “chiropractic*,” “spinal manipulation,” “carotid artery dissection,” “vertebral artery dissection,” and “stroke” across Medline and Cochrane databases. They reviewed 253 articles, narrowing them down to six relevant studies that met their inclusion criteria. The studies were independently graded for evidence quality and included in a meta-analysis using the GRADE criteria to assess the overall quality of the evidence.

Results

The meta-analysis included two class II studies and four class III studies. The combined data revealed a small association between chiropractic care and CAD, with an odds ratio (OR) of 1.74 (95% CI 1.26-2.41). However, the quality of evidence was deemed "very low" due to biases and confounding factors, particularly the known association of neck pain with both CAD and chiropractic manipulation.

Detailed Findings

Class II Studies:

  1. Smith et al. (2003) - This retrospective case-control study found an association between spinal manipulative therapy (SMT) and vertebrobasilar artery (VBA) dissection. However, limitations included recall and survivor bias, variability in diagnostic procedures, and lack of data on the reasons for chiropractic visits.

  2. Dittrich et al. (2007) - This study found no direct association between cervical manipulative therapy and CAD, but suggested that mechanical risk factors within 24 hours prior to symptom onset could be linked to CAD. The study was limited by its small sample size and potential recall bias.

Class III Studies:

  1. Rothwell et al. (2001) - This large population-based study reported an association between recent chiropractic visits and VBA, but only for patients under 45 years. The study faced limitations due to classification bias and potential unmeasured confounders.

  2. Cassidy et al. (2008) - This extensive study found that both chiropractor and primary care physician (PCP) visits were associated with VBA, suggesting that neck pain might confound the association between chiropractic care and stroke.

  3. Thomas et al. (2011) - This study identified an association between neck manual therapy and dissection, but inconsistencies in case ascertainment and lack of blinding weakened the findings.

  4. Engelter et al. (2013) - This international study found a higher incidence of cervical manipulation among CAD patients, but recall bias and heterogeneous standards for case definition were significant limitations.

Discussion

The meta-analysis suggested a small association between chiropractic care and CAD, but the evidence quality was very low. The primary challenge in establishing a causal link is the confounding factor of neck pain, which is common among CAD patients and those seeking chiropractic care. The studies reviewed showed significant biases, including recall bias, classification bias, and interviewer bias, all of which undermine the reliability of the findings.

Hill's Criteria for Causation: The analysis of the association between chiropractic care and CAD against Hill's criteria for causation revealed the following:

  1. Strength of Association: The association is modest.

  2. Consistency: Four out of five studies showed an association.

  3. Specificity: The outcome is not specific to chiropractic exposure, as seen in the equal association with PCP visits.

  4. Temporality: A temporal relationship is necessary but not sufficient for causation, with symptom onset often delayed.

  5. Biological Gradient: No data support or refute a dose-response hypothesis.

  6. Plausibility and Coherence: Biomechanical evidence does not support a significant strain on arteries from spinal manipulative therapy.

  7. Experimental Evidence: Available animal models do not support the association.

  8. Analogy: Severe trauma causes dissection, but the situation in chiropractic care is debatable.

Conclusion

The systematic review and meta-analysis by Church et al. concluded that there is no convincing evidence to support a causal link between chiropractic manipulation and CAD. The quality of the available literature is very low, and the small observed association may be due to bias and confounding factors. Misattributing causation to this association can lead to unnecessary litigation and misconceptions in medical practice.

This comprehensive review highlights the need for cautious interpretation of the existing data and underscores the importance of high-quality research to clarify the relationship between chiropractic care and CAD. For now, the evidence does not support the notion that chiropractic neck manipulation causes cervical artery dissection.

References: Church EW, Sieg EP, Zalatimo O, Hussain NS, Glantz M, Harbaugh RE. (2016). Systematic Review and Meta-analysis of Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation. Cureus, 8(2): e498. DOI: 10.7759/cureus.498

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