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 casecontrol 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 casecontrol studies and one casecontrol 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. Conclusion: 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.

Linked Comment: Ernst. Int J Clin Pract 2011; 65: 818. To the Editor: Ernst’s interesting article (1) discussed 26 published fatal cases following chiropractic treatment, emphasising vascular accidents from vertebral artery dissection (VAD) after cervical spinal manipulative therapy (cSMT), and he responded (2) to five letters (3-7). Ernst suggested that ‘causality is at least likely in such cases’ (1), but included my case where a coroner cleared cSMT from causing the stroke, which was considered more likely to be of carotid artery origin (8). This warrants consideration because only five published cases reported VAD (8-12), and in one of these (9), the practitioner involved was probably a non-chiropractor (13). This leaves only three relatively complete cases where a registered chiropractor had probably administered cSMT before a lethal stroke from VAD (10-12), and it seems impossible to determine precisely what contribution cSMT had made. The true association of cSMT with VAD stroke remains unknown because of limitations regarding the relevant epidemiological studies (14-16). It may be only a weak association for the commonly used cSMTs, and similar to that for neck mobilising. Two studies involving physiotherapists who used cSMT and neck mobilising found two stroke cases for both mobilising and cSMT (17, 18). Ernst stated that ‘...chiropractors routinely employ high velocity...thrusts on the upper cervical spine with a rotational element...’ but this is a likely over-generalisation. My Perth survey (56% response rate) found 90% of chiropractor respondents replying that they seldom or never used rotatory cSMT (19). Based on a 1994 Perth survey (20) and recent data (21, 22), an estimated half million Western Australian adults (30%) have attended a chiropractor. Apparently, no Western Australian chiropractor has been found responsible for a death. While under-reporting in journals is expected as a result of publishing bias, this is less likely in the media, which reports coroner inquests of these VAD deaths. This supports Wenban and Bennet’s suggestion of extremely low risk (3). When criticised for describing his review as ‘systematic’ (7), Ernst explained that systematic review criteria for case studies are unformulated (2). Perhaps this term should only be used when the criteria are determined and followed. Ernst (1) omitted discussing misclassification bias regarding ‘chiropractor’ and ‘chiropractic’ (8, 13, 23), and was dismissive of three such examples (2) in his review that Wenban and Bennett revealed (5). However, similarly biased cases could have been listed, but had missed author survey (13, 23). I agree with others (6, 7) that Ernst’s claim ‘...The risks of chiropractic neck manipulation by far outweigh the benefits’ is unsupported by his results partly because they lack accurate data on cSMT benefits. Listed were 26 published fatal cases that supposedly implicated chiropractic over 76 years internationally, so in this context are arguably not ‘numerous’. Ernst’s article, which emphasised cSMT, is potentially misleading because it also failed to disclose five non-cSMT cases from the nine internet sourced cases, as Perle et al. revealed (6), and omitted the coroner’s exoneration of chiropractic in the unpublished Mathiason case (24). Analysing the under-reporting of adverse events inaccurately reflects cSMT risk, which will need improved epidemiological studies to measure properly. Considering the limitations of the relevant studies, caution is required on both sides of the debate when discussing the risk/benefit of cSMT. I have no financial conflicts of interest and have had no funding regarding my submission. There are no acknowledgements to be made.

Objective To determine whether the presence of posterior ponticles markedly increases by 30% or more, the incidence of major rotational stenosis of vertebral arteries. Methods Doppler ultrasound studies were performed in 3 private chiropractic clinics and in the radiology department of a public hospital, and magnetic resonance angiography (MRA) studies were made in the latter location. Thirty-two chiropractic patients had Doppler velocimetery, and 16 of these patients had MRA scanning. The outcome measures included changes in Doppler velocimetry signals and MRA images indicative of marked rotational stenosis of vertebral arteries. Results All vertebral arteries from the 32 patients displayed no signs indicative of marked rotational stenosis. Conclusion The findings of this study show that the incidence of major rotational stenosis of vertebral arteries is not markedly increased by the presence of posterior ponticles.

OBJECTIVE:It has been proposed that Doppler velocimetry, which is noninvasive, quick, and relatively inexpensive, should be used when the screening vertebral arteries before manipulation to reduce the risk of cervical manipulation-related injury to these vessels. The objective of this analysis of the literature is to study the evidence of the suitability of Doppler velocimetry for this purpose.DATA SELECTION:Studies were examined that dealt with the incidence of stroke after manipulation, the proposed mechanisms for this clinical entity, the validity of the provocational tests that have been used in screening before manipulation, the validity and reliability of Doppler velocimetry of vertebral arteries, and the biomechanics of vertebral arteries.RESULTS:There is a suspicion of increased risk for vertebrobasilar stroke for vertebral arteries that have markedly reduced patency in the neutral position and/or stenosis during cervical rotation. There is evidence that provocational tests lack validity and that Doppler velocimetry is valid in assessing the patency of vertebral arteries in the neutral position and during cervical rotation. Interexaminer reliability of the Doppler technique has been shown to be high. Doppler ultrasound screening also seems to be able to provide an indirect assessment of the mechanical stresses to the artery during cervical movements.CONCLUSION:There is strong evidence to suggest that Doppler velocimetry should be included in the screening of vertebral arteries before manipulation.

Objective: To determine whether lumen narrowing in vertebral arteries during atlanto-axial rotation is due to stretch or localized compression.Design and Setting: Experiments with models were made in a private chiropractic clinic, whereas studies of cadaveric specimens were performed in an anatomy laboratory. Doppler ultrasound and magnetic resonance angiography (MRA) studies were carried out in the radiology department of a public hospital.Patients: Eight patients had their vertebral arteries examined by use of a Doppler velocimeter and MRA.Main Outcome Measure: Stenosis of the vertebral arteries caused by stretch, localized compression, or kinking.Results: All 16 vertebral arteries from the 8 patients displayed no changes in their lumen dimensions with full cervical rotation, although curves in each of the arteries did change. The model and cadaveric vertebral arteries demonstrated localized compression or kinking of the vessel wall with atlanto-axial rotation contralaterally but revealed no evidence of major contribution of stretching to stenosis.Conclusion: The lumen of vertebral arteries is usually unaffected by atlanto-axial rotation. In cases where there is stenosis, this is mainly due to localized compression or kinking. These findings are relevant to premanipulative screening of vertebral arteries with Doppler ultrasound scanning.

OBJECTIVES:To assess the reliability of the SpinT, a new protractor-based device, for measuring active cervical spine ranges of motion. In addition, to compare the accuracy of the Cervical Ranges of Motion (CROM) instrument and SpinT measurements of rotation about the Y axis with and without tilt, the former motion occurring during natural rotation of the head. STUDY DESIGN:Interexaminer reliability, intraexaminer reliability, and accuracy trials were conducted. METHODS:Two examiners made 2 individual measurements of each of the individual cervical ranges of motion of 23 patients (15 men, 8 women; aged 21 to 42 years) with no cervical symptoms. The patients were asked to move their necks to end range while they sat upright. The accuracy of the CROM instrument and SpinT goniometers was assessed with a testing instrument capable of rotating and/or tilting to preset angles and upon which either device could be positioned. RESULTS:There was excellent agreement between the SpinT measurements of rotation about the Y axis compared with the readings from the testing platform regardless of the angle of tilt, whereas the CROM instrument displayed poor concordance when the tilt exceeded 5 degrees. The reliability trials generally yielded close agreement between the examiners, especially regarding measurements of rotation left and right and extension and revealed higher concordance regarding intraexaminer results. CONCLUSION:This study indicates that SpinT measurements of active cervical ranges of motion are reliable and that the SpinT goniometer accurately measures rotation with associated tilt.

Purpose. The aims of this study were to determine whether vertebral artery blood flow velocity changes during contralateral cervical rotation, to determine the extent of rotation necessary to affect the velocity, and to find direct evidence of stretching or compression of the vertebral arteries during cervical rotation.Methods. Color duplex sonography was used to measure the blood flow velocities and diameters of the vertebral arteries in 20 patients. Measurements were taken with the patients' heads in the neutral position and at 10 degrees increments of contralateral neck rotation (determined using a cervical range of motion goniometer) to the end-range.Results. The data showed no significant change in the mean blood flow velocity for the entire study population during cervical rotation. However, there were marked changes in the blood flow velocities in 7 vertebral arteries toward the end-range of rotation. No arteries displayed any evidence of major stretching of the arterial walls, although localized compression of 2 arteries was observed.Conclusions. The results of this study suggest that vertebral arteries are usually unaffected by contralateral cervical rotation and that Doppler sonography may provide an indirect assessment of mechanical stresses to the arterial wall. (C) 2000 John Wiley & Sons, Inc.

The purpose of this study was to test the interexaminer reliability of Doppler ultrasound (US) velocimeter examination of vertebral arteries during contralateral cervical rotation. Vertebral arteries from 20 adults were insonated using a bidirectional Doppler velocimeter at the suboccipital portal (standard technique) and C2 transverse process level (new technique) during contralateral cervical rotation. The data obtained by two examiners, regarding persistence or major reduction in Doppler signals, were compared. There was 93% agreement between the data from the two examiners, and the kappa score was 0.78 at p = 0.05. These results provide evidence to support the interexaminer reliability of bidirectional Doppler velocimeter examination for the purpose of assessing the effects of contralateral rotation on vertebral artery blood flow.

The purpose of this study was to test the validity of Doppler ultrasound (US) velocimeter examination of vertebral arteries during contralateral (to the opposite side) cervical rotation. Vertebral arteries from 20 subjects were insonated using a bidirectional Doppler velocimeter at the suboccipital portal (standard technique) and C2 transverse process level (new technique) during contralateral cervical rotation. The results, regarding persistence or major reduction in Doppler signals, were then compared with those from a colour-flow duplex US scanner using the same procedure. There was complete agreement between the combined suboccipital and C2 velocimeter results and those from the duplex scanner (k = 1.00 at p = 0.01): both sensitivity (n = 5) and specificity (n = 34) were 100%. This study provides evidence to support the validity of bidirectional Doppler velocimeter examination, by an experienced examiner, for the purpose of assessing the effects of contralateral rotation on vertebral artery blood flow.