Research Review By Dr. Demetry Assimakopoulos©


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Date Posted:

May 2019

Study Title:

A Risk-Benefit Assessment Strategy to Exclude Cervical Artery Dissection in Spinal Manipulative Therapy: A Comprehensive Review


Chaibi A & Russell MB

Author's Affiliations:

Head and Neck Research Group, Research Centre, Akershus University Hospital, Oslo Norway; Institute of Clinical Medicine, Akershus University Hospital, University of Oslo, Norbyhagen, Norway.

Publication Information:

Annals of Medicine 2019; Mar 19: 1-10. doi: 10.1080/07853890.2019.1590627.

Background Information:

Cervical artery dissection (CAD) is defined as a tear in the internal carotid (ICA) or vertebral (VA) arteries, resulting in an intramural hematoma and/or aneurysmal dilatation. The pathophysiology of CAD is not robustly understood but is believed to be associated with coexisting pathological processes which increase the risk of arterial wall weakness, such as hypertension and arterial wall stiffness (1). Fortunately, the annual incidence of CAD is relatively low, estimated to be approximately 2.9/100 000 individuals.

It is imperative for all clinicians to be well informed about the possible red flags associated with CAD. As such, the authors of this clinical review described the epidemiology and pathology of CAD, discussed the risks that may or may not be associated with cervical spine manipulation, and the pertinent findings associated with this serious condition. They also provided a step-by-step risk-benefit assessment strategy tool for manual therapists to aid in clinical decision-making.


General Characteristics of CADs:

The average patient age for CAD is approximately 44-years (average approximately 46 for men and 41 for women). CAD is extremely rare in children and in people beyond the age of 65. ICA dissections (ICADs) are known to occur 3-5x more frequently than VA dissections (VADs). Headache and/or neck pain are the most common symptoms of CAD. Headaches from CAD are typically sudden, new and unilateral, and often resemble symptoms of migraine or cluster headache. The time from initial symptoms to overt stroke may be minutes to several weeks (3 ,4). While CAD is typically thought to occur spontaneously, trauma to the neck, especially with concomitant hyperextension and rotation, are suspected triggers.

Many sufferers seek manual therapies for the CAD prodromal headache and neck pain symptoms. Some case reports have thus suggested that CAD may be an adverse event (AE) from manual therapies, including SMT (7-14). It is important to note, however, that claims linking cervical manual therapy techniques to CAD have been hotly contested, as the current evidence cannot establish a causal relationship between SMT and CAD due to the rarity of the condition and poor methodological quality of most existing studies. The rarity of CAD makes epidemiological study challenging (although big data is improving this capability). Several cohort studies and meta-analyses to date have found no excess risk of CAD causing secondary ischaemic stroke from SMT compared to primary care (15). Other invasive studies have demonstrated that cervical SMT does not exceed the VA failure strain or change VA blood flow velocity (16-18). In light of this amalgamation of data, the body of literature has concluded that that no strong evidence exists to causally link manual therapy to CAD.

The Internal Carotid Artery (ICA):

The ICA provides the greatest proportion of blood flow to the brain, with preference to the anterior regions, including the retina. Any disruption to anterior circulation can cause retinal and/or cerebral ischemic symptoms, such as hemiparesis, hemisensory loss, neglect, aphasia, gaze deviation, dysarthria and monocular visual loss. While the pain from ICAD can vary, it often presents unilaterally in the neck, or periorbital, frontal or upper anterior cervical regions. Associated headaches are usually severe and can resemble migraine or cluster headaches. Pathophysiologically, ICA ruptures can cause subarachoid hemorrhage, leading to abrupt severe headaches. However, to complicate the picture further, symptoms can also be incredibly mild and even go undetected. When local symptoms are secondary to compression of adjacent structures, such as an aneurysm formation, cranial nerve symptoms become obvious as they lay within close proximity to the dissection. Cranial nerves IX-XII are most typically affected. Because ICAD lesions are often intracranial, it is highly unlikely that mobilization or SMT can affect the ICA.

Vertebral Artery (VA):

Contrary to the ICA, the VA primarily supplies the posterior portion of the brain. Disruption to the posterior circulation may produce brainstem ischemic symptoms, such as ipsilateral loss of pain sensation (nociception) and hemiparesis, contralateral loss of temperature sensations, nausea, vomiting, vertigo, nystagmus, diplopia, dysphagia, dysarthria and dysphonia. Cerebellar symptoms, such as ataxia, vertigo and nystagmus can also manifest. The pain associated with VAD is often sudden and new, and most commonly presents in the unilateral suboccipital region. Because of the VA’s location within the vertebral foramen, it is thought to be more susceptible to mechanical trauma from extreme rotational head movements of the upper cervical spine (19). However, all people perform several different head and neck movements every day, including motions that dynamically stretch the VA. Fortunately, these movements usually do not trigger CAD.

Neck Pain and CAD:

Neck pain co-existing with CAD is often described as sudden, sharp, severe, steady and different from previously experienced neck pains (20, 21). CAD should be ruled out through careful history and thorough examination, particularly if patients present with neurological signs or symptoms. Unfortunately, most clinical examination techniques/tests have little to no proven usefulness unless radiculopathy or serious structural compromise are strongly suspected (22). A possible red flag indicator, although not strictly pathognomonic, is a lack of change in symptoms to mechanical provocation manoeuvres. A clinical indicator of a vascular etiology is a lack of analgesic effect from NSAIDs. CAD should also be suspected (until proven otherwise) in any cases where neurological deficits are present along with a history of MSK complaints (again, not pathognomonic).

Risk-Benefit Identification Strategy Assessment Tool:

Clinicians should be specifically aware of certain historical factors, including:
  • Recent acute respiratory infection
  • Hyperhomocysteinaemia
  • Vitamin deficiencies (B6, B9 or B12)
  • Low BMI
  • Low cholesterol
  • Smoking
  • Pulsating tinnitus
  • Family history of arterial anomalies and/or CAD
  • Family history of connective tissue disorders (i.e. Ehlers-Danlos Syndrome Type IV, Osteogenesis Imperfecta or Loeys-Dietz Syndrome)
≥ 2 Distinct Symptoms Should Warrant Referral to ER to Query ICA Dissection
  • Recent head, neck or thoracic trauma
  • New ipsilateral periorbital, frontal or upper back pain
  • Distinct, new and continued headache
  • Partial Horner’s Syndrome
  • Retinal and/or cerebral ischemic symptoms
  • If < 2 symptoms, progress to physical examination
2 Distinct Symptoms Should Warrant Referral to ER to Query VA Dissection
  • Recent head, neck or thoracic trauma
  • New, ipsilateral suboccipital neck pain
  • Distinct, new and continued headache
  • Brainstem ischemic symptoms
  • Cerebellar ischemic symptoms
  • If < 2 symptoms, progress to physical examination
If 2 Positive Physical Tests are present, refer directly to ER
  • Cranial Nerve Palsy IX, X, XI, XII (CAD) or Cervical Radiculopathy (C5-6, more specific to VAD)
  • Hypertension > 140/90
  • Neck Swelling
  • Midline tenderness suggestive of fracture
If the above historical and physical findings are negative, the authors recommend minimizing end-range cervical manual therapies (especially rotational techniques), to be as specific as possible to the affected vertebral segment, to minimize force/amplitude, and to appraise pre-manipulative status using cervical mechanical provocation testing procedures.

Clinical Application & Conclusions:

This review described the epidemiology and potential clinical symptoms of CADs, as they relate to chiropractic and manual therapy. The authors also outlined a systematic approach to screen for CADs called the Risk-Benefit Analysis Tool. They also discuss a few truths that have been firmly addressed and confirmed in the literature, namely that:
  1. There is no firm scientific basis for direct causality between cervical SMT and arterial dissection.
  2. The ICA moves freely within the cervical pathway.
  3. ~75% of cervical SMTs are conducted in the lower cervical spine, where the VA moves freely.
  4. Active daily life consists of multiple cervical movements including rotations and other activities that do not trigger CAD.
  5. A cervical manipulation goes beyond the physiological limit but remains within the vessels’ anatomical range, theoretically implying that the artery should not exceed failure strain.
They add that further research should be directed towards early detection and exclusion of CAD to minimize risk. Primary care clinicians should prudently dedicate time for thorough history taking and physical examination. Any signs or symptoms identified through the algorithm detailed above warrants immediate referral to the ER. Further, it remains prudent advice to be cautious and trust your instincts if a particular case just doesn’t add up. This will most importantly protect the safety of your patient and also help insulate you from potential legal action!

Study Methods:

This was a narrative review. As such, no literature search strategy was outlined, nor any formal statistical analysis performed.

Study Strengths / Weaknesses:

The authors provided a well-referenced synthesis that dispels many of the myths associated with cervical manipulation using high-quality basic science and available epidemiological studies. They supported these findings by describing both the anatomy and pathophysiology of the ICA and VA as it pertains to manual therapy interventions, specifically cervical SMT.

Unfortunately, the above-mentioned Risk-Benefit Strategy Assessment has not been clinically evaluated for sensitivity, specificity, reliability and validity in clinical settings. One should note, however, that since the incidence and prevalence of CADs are relatively low, making such a statistical analysis would be extremely difficult. Additionally, the authors paradoxically argue on the one hand that low force, non-end range cervical manual therapies should be utilized. However, on the other hand, the authors state that these above-mentioned factors should not matter given that SMT does not exceed the VA and ICA failure strains, and that relatively few adverse events have been reported in large prospective studies. This contradiction is peculiar.

Additional References:

  1. Debette S. Pathophysiology and risk factors of cervical artery dissection: what have we learnt from large hospital-based cohorts? Current Opinion in Neurology 2014; 27(1): 20-8.
  2. Metso AJ, Metso TM, Debette S, et al. Gender and cervical artery dissection. Eur J Neurol 2012; 19(4): 594-602.
  3. CHD. Headache Classification Committee of the International Headache Society (IHS) The International Classification of Headache Disorders, 3rd edition. Cephalalgia 2018; 38(1): 1- 211.
  4. Cadena R. Cervical artery dissection: early recognition and stroke prevention. Emergency Medicine Practice 2016; 18(7): 1-24.
  5. Olesen J, Goadsby PJ, Ramadan NM, et al. The Headache. 3rd ed. USA: Lippincott Williams & Wilkins; 2006.
  6. Debette S, Leys D. Cervical-artery dissections: predisposing factors, diagnosis, and outcome. Lancet Neurol 2009; 8(7): 668-678.
  7. Haldeman S, Carey P, Townsend M, et al. Arterial dissections following cervical manipulation: the chiropractic experience. CMAJ 2001; 165(7): 905-906.
  8. Cassidy JD, Boyle E, Cote P, et al. Risk of vertebrobasilar stroke and chiropractic care: results of a population-based case-control and case-crossover study. Spine 2008; 33(4 Suppl): S176-S183.
  9. Rubinstein SM. Adverse events following chiropractic care for subjects with neck or low-back pain: do the benefits outweigh the risks? J Manipulative Physiol Ther 2008; 31(6): 461-4.
  10. Tuchin P. A replication of the study 'Adverse effects of spinal manipulation: a systematic review'. Chiro Man Ther 2012; 20(1): 30.
  11. Wynd S, Westaway M, Vohra S, et al. The quality of reports on cervical arterial dissection following cervical spinal manipulation. PloS One 2013; 8(3): e59170.
  12. Chung CL, Cote P, Stern P, et al. The Association Between Cervical Spine Manipulation and Carotid Artery Dissection: A Systematic Review of the Literature. J Manipulative Physiol Ther 2015; 38(9): 672-6.
  13. Cassidy JD, Boyle E, Cote P, et al. Risk of Carotid Stroke after Chiropractic Care: A Population- Based Case-Crossover Study. Journal of Stroke and Cerebrovascular Diseases 2017; 26(4): 842-850.
  14. Kranenburg HA, Schmitt MA, Puentedura EJ, et al. Adverse events associated with the use of cervical spine manipulation or mobilization and patient characteristics: A systematic review. Musculoskel Sci Practice 2017; 28: 32-38.
  15. Church EW, Sieg EP, Zalatimo O, et al. Systematic Review and Meta-analysis of Chiropractic Care and Cervical Artery Dissection: No Evidence for Causation. Cureus 2016; 8(2): e498.
  16. Herzog W, Leonard TR, Symons B, et al. Vertebral artery strains during high-speed, low amplitude cervical spinal manipulation. J Electromyogr Kinesiol 2012; 22(5): 740-746.
  17. Piper SL, Howarth SJ, Triano J, et al. Quantifying strain in the vertebral artery with simultaneous motion analysis of the head and neck: a preliminary investigation. Clin Biomech 2014; 29(10): 1099-107.
  18. Quesnele JJ, Triano JJ, Noseworthy MD, et al. Changes in vertebral artery blood flow following various head positions and cervical spine manipulation. J Manipulative Physiol Ther 2014; 37(1): 22-31.
  19. Reddy M, Reddy B, Schoggl A, et al. The complexity of trauma to the cranio-cervical junction: correlation of clinical presentation with Doppler flow velocities in the V3-segment of the vertebral arteries. Acta Neurochirurgica 2002; 144(6): 575-80; discussion 580.
  20. Silbert PL, Mokri B, Schievink WI. Headache and neck pain in spontaneous internal carotid and vertebral artery dissections. Neurology 1995; 45(8): 1517-22.
  21. Arnold M, Bousser MG. Clinical manifestations of vertebral artery dissection. Frontiers of Neurology and Neuroscience 2005; 20: 77-86.
  22. Nordin M, Carragee EJ, Hogg-Johnson S, et al. Assessment of neck pain and its associated disorders: results of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders. Spine 2008; 33(4 Suppl): S101-22.
  23. Kerry R, Taylor AJ, Mitchell J, et al. Manual therapy and cervical arterial dysfunction, directions for the future: a clinical perspective. J Man Manip Ther 2008; 16(1): 39-48.

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