title: Assessing the risk of stroke from neck manipulation: a systematic review.
abstract: BACKGROUND
  Strokes, typically involving vertebral artery dissection, can follow cervical spinal manipulative therapy, and these types of stroke occur rarely. There is disagreement about whether a strong association between neck manipulation and stroke exists. An earlier systematic review found two relevant studies of association that used controls, which also discussed the limitations of the two papers. Our systematic review updates the earlier review, and aims to determine whether conclusive evidence of a strong association exists.
  
  
  METHODS
  PRISMA guidelines for systematic reviews were followed, and the literature was searched using a strategy that included the terms 'neck manipulation' and 'stroke' from the PubMed, Embase, CINAHL Plus and AMED databases. Citations were included if they met criteria such as being case-control studies, and dealt with neck manipulation and/or neck movement/positioning. Papers were scored for their quality, using similar criteria to the earlier review. For individual criteria, each study was assigned a full positive score if the criterion was satisfied completely.
  
  
  RESULTS
  Four case-control studies and one case-control study, which included a case- crossover design, met the selection criteria, but all of them had at least three items in the quality assessment that failed to be completely positive. Two studies were assessed to be the most robustly designed, one indicating a strong association between stroke and various intensities of neck movement, including manipulation, and the other suggesting a much reduced relative association when using primary care practitioners' visits as controls. However, potential biases and confounders render the results inconclusive.
  
  
  CONCLUSIONS
  Conclusive evidence is lacking for a strong association between neck manipulation and stroke, but is also absent for no association. Future studies of association will need to minimise potential biases and confounders, and ideally have sufficient numbers of cases to allow subgroup analysis for different types of neck manipulation and neck movement.
authors.affiliation: The University of Western Australia, Crawley, WA, Australia. mhaynes@fastmail.fm
authors.forename: M J
authors.initials: MJ
authors.lastname: Haynes
authors.forename: K
authors.initials: K
authors.lastname: Vincent
authors.forename: C
authors.initials: C
authors.lastname: Fischhoff
authors.forename: A P
authors.initials: AP
authors.lastname: Bremner
authors.forename: O
authors.initials: O
authors.lastname: Lanlo
authors.forename: G J
authors.initials: GJ
authors.lastname: Hankey
mesh_terms: D015982:Bias; D020215:Carotid Artery, Internal, Dissection / Q000209:etiology; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D026882:Manipulation, Chiropractic / Q000009:adverse effects; D020393:Manipulation, Spinal / Q000009:adverse effects*; D012307:Risk Factors; D020521:Stroke / Q000209:etiology*; D020217:Vertebral Artery Dissection / Q000209:etiology