Cervical artery dissection (CeAD) is the most serious safety concern related to the provision of high-velocity, low-amplitude cervical spinal manipulation (SMT) and can involve the carotid or vertebral arteries. The pathology of concern is dissection, which occurs when the arterial lining deteriorates, allowing blood to penetrate the artery wall. This dissection and/or the potential associated thrombus can occlude the artery, or the thrombus can embolize and cause ischemic stroke. Patients with CeAD may in fact be asymptomatic, however they frequently experience clinical manifestations of neck pain and headache. These symptoms may then prompt them to seek care from a chiropractor, or other health care provider.
Trauma can lead to CeAD, but many are considered to be spontaneous in origin. Of concern to chiropractors and other manual therapy clinicians is the strong association that has been reported between CeAD-associated stroke and ‘trivial trauma’, which can include cervical SMT (and many other daily activities). Despite CAD occurring more frequently than VAD, the reported predominance of VADs following SMT versus CADs is 3:1.
One of the proposed mechanisms for the association between VAD and cervical SMT is that rotation and extension of the neck can stretch the vertebral artery in the upper cervical spine, despite no direct evidence to support this hypothesis (in addition to recent cadaver evidence [from Gorrell and colleagues] – that we reviewed in 2023 – suggesting that the VA doesn’t experience any tensile force during SMT movement – rather, the existing slack is taken out of the structure during manipulation).
We know that cervical SMT is a common, evidence-based treatment for neck pain and headaches, and we know that patients with emerging or developing CeAD may experience and seek care for these symptoms. Since the true risk of CeAD in relation to SMT remains unclear, a rigorous examination of the association between SMT and CeAD is warranted. Since CeAD is so rare, evaluating this in an interventional (prospective) study would require a prohibitively large sample size, so we must rely on other methodologies, such as a case-control approach.
The increasing availability of large datasets from private insurance claims allows for such investigation and affords sufficient statistical power to better quantify the risk. This study (one of many we have reviewed in recent years from Dr. Whedon and colleagues) analyzed claims data spanning a nine-year period and employed case-control and case-crossover designs to evaluate the association between cervical SMT and CeAD among privately insured adults aged 18 years and over in the United States. These authors attempted to address shortcomings of previous work in this area by using three different control groups to assess the sensitivity of their results.
From Dr. Thistle:
“In practice, it is our job to attempt to identify a patient who may be experiencing symptoms of a stroke in progress, so they can be referred accordingly. This can be best achieved via the combination of a careful clinical history and examination, with special consideration to the emergence or presence of severe neck pain and/or an atypical headache (specifically, the ‘sentinel’ headache variety). If a patient is seeing you for the first time, remember that it is difficult to put the severity of their symptoms into context (compared to a patient you have seen over time) – this can make the identification of a ‘sentinel’ headache or severe, emergent neck pain difficult to identify. Trust your instincts and be sure to obtain a clear picture from the patient as to the severity and temporal evolution of their current symptoms compared to any prior episodes of head or neck pain they have experienced.”
RESEARCH REVIEW: Association Between Cervical Artery Dissection & Spinal Manipulation Among American Adults
This paper was published in the European Spine Journal (2023).