Vertebral Artery Dissection and Chiropractors

Vertebral artery dissection is a tear in the inner lining of one of the arteries running through the neck to the brain, and it is a leading cause of stroke in younger, otherwise healthy adults. Whether chiropractic neck manipulation can trigger this tear has been debated in neurology and chiropractic research for decades, and the honest answer is that the question remains unsettled. Biomechanical studies suggest the forces involved in a typical adjustment fall well below what the artery can tolerate, yet population-level studies have found a statistical association between recent chiropractic visits and vertebrobasilar stroke in younger patients. Untangling cause from coincidence is the central challenge, and understanding it matters for anyone considering cervical spine manipulation.

What Happens Inside the Artery

The vertebral arteries are a pair of blood vessels that thread through small bony canals in the cervical vertebrae before merging at the base of the skull to supply the brainstem and the back of the brain. A dissection occurs when a tear forms in the artery’s inner wall, allowing blood to seep between the vessel’s layers. That blood can pool and form a clot, narrowing or blocking the artery, or it can balloon outward as a pseudoaneurysm. Either scenario can reduce blood flow to the brainstem and cerebellum, and a clot fragment can break loose and cause a posterior circulation stroke.

Most vertebral artery dissections are classified as “spontaneous,” meaning they happen without major trauma like a car crash. But “spontaneous” does not mean “without cause.” Minor mechanical events, underlying weakness in the artery wall, or a combination of both can set the stage. The real difficulty for clinicians is that symptoms often begin before anyone realizes something has gone wrong inside the vessel.

Why Chiropractic Visits and Stroke Overlap in the Data

A Canadian population-based study found that people under 45 who had a vertebrobasilar stroke were five times more likely to have visited a chiropractor in the preceding week, and five times more likely to have had three or more chiropractic visits with a cervical complaint in the prior month, compared with matched controls. No such association was found in patients 45 and older.

That finding, published in the journal Stroke, has been widely cited. But a later and larger Canadian case-control and case-crossover study compared stroke risk after chiropractic visits to stroke risk after primary care visits for the same complaints. It found no evidence of excess vertebrobasilar stroke risk from chiropractic care compared with seeing a family doctor.

The implication is striking: patients who are already in the early stages of a dissection develop neck pain and headache, and they seek care for those symptoms. Some go to a chiropractor; some go to their doctor. The stroke that follows may look like a consequence of the visit when it is actually the reason for the visit. Researchers call this protopathic bias, and it makes it extremely hard to tease apart whether manipulation caused the dissection or whether the dissection drove the appointment.

A study of Medicare beneficiaries aged 66 to 99 with neck pain found that the risk of stroke within seven days was actually lower for those who saw a chiropractor than for those who saw a primary care provider. At 30 days, there was a very slight elevation for the chiropractic group, but the difference was small.

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What the Biomechanical Evidence Shows

If cervical manipulation were mechanically capable of tearing a healthy vertebral artery, you would expect to see substantial strain on the vessel during the thrust. Several cadaver studies have tried to measure exactly that.

One widely cited study found that vertebral artery strains during high-speed, low-amplitude cervical manipulation were significantly smaller than strains during ordinary diagnostic range-of-motion testing, and were far smaller than the forces needed to tear the artery outright. The researchers concluded that manipulation by trained clinicians does not appear to place undue strain on the vertebral artery.

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A more recent observational study measured maximal vertebral artery strain at different cervical levels during manipulation. The average peak strain during the thrust phase was about 1.1%, while the arteries in the same cadavers could be stretched on average more than 50% before they failed.

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Another cadaver study reported that the greatest average change in vertebral artery length during manipulation was about 5%, while the vessels had to be stretched an average of roughly 51% before they actually failed.

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These numbers suggest a wide margin of safety in normal arteries. But cadaver arteries may not perfectly represent living tissue, and the research cannot account for arteries that are already weakened by disease, genetic predisposition, or early-stage dissection. The gap between “normal artery tolerates manipulation fine” and “already-compromised artery does not” remains the critical unknown.

Who Is More Vulnerable

Most vertebral artery dissections occur in people between their mid-30s and late 40s, and many of these people have no obvious risk factors. But connective tissue disorders stand out in the research. Ehlers-Danlos syndrome, particularly the vascular type caused by mutations in the COL3A1 gene, produces fragile arteries prone to tearing. About a quarter of the vascular complications in this condition involve arteries above the aorta, including those in the neck.

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You do not need to carry a known diagnosis to have vulnerable arteries. A study using electron microscopy found structural abnormalities in the arterial connective tissue of more than half of patients with cervical artery dissection, sometimes resembling the changes seen in Ehlers-Danlos syndrome even when patients did not meet the formal diagnostic criteria.

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Other recognized contributors include underlying arteriopathies, fibromuscular dysplasia, and simple mechanical forces like trauma or vigorous neck movements. In many cases, it is likely a combination of subtle vessel-wall weakness and some form of mechanical stress, even minor stress, rather than any single trigger.

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A systematic review of adverse events after cervical spine manipulation noted that women appear to be more at risk for cervical artery dissection, though patient characteristics have generally been described poorly in the literature.

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The Symptom Overlap Problem

This is where the situation gets genuinely tricky. The early symptoms of vertebral artery dissection are neck pain and headache, exactly the complaints that send people to a chiropractor in the first place. A systematic review of case reports involving patients with undiagnosed vertebral artery dissection who presented to chiropractors found that every single patient had either neck pain or headache. Neck pain was present in nine out of ten, headache in eight out of ten, and visual disturbance and dizziness appeared in roughly half and four in ten patients, respectively.

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A broader systematic review of symptomatic vertebral artery dissection across all clinical settings found a similar pattern: dizziness or vertigo was the most common symptom at about 58%, followed by headache at roughly 51% and neck pain at about 46%. Around three-quarters of patients had head or neck pain at some point during their presentation, which means almost one in four had no craniocervical pain at all.

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The overlap creates a genuine clinical dilemma. A patient walks in complaining of new-onset neck pain and a headache. That could be a straightforward musculoskeletal complaint, or it could be the opening act of a dissection in progress. There is no reliable bedside test to distinguish the two.

Why Pre-Manipulation Screening Tests Do Not Work

For years, many chiropractic and physical therapy guidelines recommended performing vertebrobasilar insufficiency tests before cervical manipulation, typically holding the patient’s head in certain rotated or extended positions and watching for dizziness, nystagmus, or other neurological signs. The logic seemed sound: provoke a temporary reduction in blood flow through the vertebral arteries, and if the patient develops symptoms, do not proceed.

The evidence, however, is that these tests do not meaningfully predict who is at risk. A systematic review of their diagnostic accuracy found sensitivity as low as zero and no higher than 57%, meaning the tests miss a large proportion of people who actually have a problem.

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A more pointed commentary in Musculoskeletal Science and Practice argued that these positional tests should be abandoned entirely. The underlying mechanism they rely on, producing decreased blood flow in the opposite vertebral artery, does not even work consistently in healthy people. Multiple case reports describe serious neurovascular events occurring after a negative screening test, creating a false sense of security. The author concluded that a negative test result can be wrongly interpreted as “safe to manipulate” and that the tests have no added value beyond a careful patient interview.

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What does have value is a thorough history: asking about recent trauma, unusual headache patterns, visual changes, dizziness, and family history of connective tissue problems. None of these questions are perfect, but they perform better than positional testing at flagging patients who need imaging before any manual therapy.

Diagnosing a Dissection

When a vertebral artery dissection is suspected, the gold standard involves vascular imaging. MRI, MR angiography, and CT angiography all perform relatively similarly for detecting carotid and vertebral artery dissections.

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High-resolution MRI of the vessel wall has shown advantages in the acute and subacute phases, particularly for detecting the intimal flap or double-lumen sign that confirms a dissection, compared with standard MR angiography alone. In the chronic stage, the differences between techniques become less meaningful.

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For most emergency departments, CT angiography is the fastest and most accessible option. If you develop sudden severe neck pain, an unusual headache, dizziness, visual disturbance, or weakness on one side of the body, particularly after any form of neck manipulation or even a minor mechanical event, urgent imaging is the right step.

Treatment After a Dissection Is Confirmed

The primary goal of treatment is preventing a stroke. That means blood thinners, either antiplatelet drugs or anticoagulants, to keep clots from forming at the dissection site and traveling to the brain. The question of which type works better has been studied directly.

The CADISS trial, the largest randomized trial on this question, enrolled 250 patients with cervical artery dissection and compared antiplatelet therapy to anticoagulation. The recurrent stroke rate at one year was low in both groups, roughly 2.5%, with no significant difference between the two approaches. Vessel healing at three months was also similar regardless of which drug patients received.

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A later meta-analysis pooling individual patient data from randomized trials suggested that anticoagulation might be associated with fewer strokes compared with aspirin alone, but also with more bleeding events. The primary combined endpoint did not reach statistical significance.

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In practice, many neurologists choose anticoagulation for patients with severe narrowing or large clot burden, and antiplatelet therapy for less severe cases, but this is guided more by clinical judgment than by strong trial data favoring one approach over the other.

How Dissections Heal

Vertebral artery dissections often improve on their own, though the timeline and completeness of healing vary. A study using serial MR angiography found complete healing in some vessels, improvement in others, and persistence of the dissection in a minority. Stenosis and blood within the artery wall were the features most likely to resolve, while complete occlusion and luminal irregularity tended to persist. Late strokes in that series occurred in patients whose dissections had not healed, including one who stopped anticoagulation prematurely.

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Most patients do not have recurrent dissections. The overall prognosis depends heavily on whether a stroke occurs before treatment begins. A dissection caught early and treated with blood thinners has a good outlook. A dissection that presents with a completed stroke carries the prognosis of any posterior circulation stroke, which ranges from full recovery to permanent disability depending on the size and location of the affected brain tissue.

Mobilization as an Alternative to High-Velocity Manipulation

The chiropractic and manual therapy professions distinguish between high-velocity, low-amplitude thrust manipulation and gentler mobilization techniques that move the joint within its normal range without a sudden thrust. Since the theoretical concern with dissection involves rapid rotation or extension of the neck, mobilization has been promoted as a potentially safer alternative for patients at higher risk.

A clinical commentary comparing the two approaches noted that certain conditions are common contraindications to thrust manipulation, including fractures, cancer, osteoporosis, and vertebral artery stenosis. The same commentary acknowledged an association between cervical thrust manipulation and vertebrobasilar stroke, while noting that population-level studies have not found excess risk compared to primary care visits for similar complaints.

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Whether mobilization carries a meaningfully lower risk of vascular injury than thrust manipulation has not been studied in a controlled trial. The biomechanical data suggest that even thrust manipulation places relatively low strain on healthy arteries, so the safety margin may be large for either technique. But in a patient with suspected vascular vulnerability, many clinicians favor mobilization, soft-tissue work, or non-manual approaches simply to avoid the theoretical worst case.

The Reporting Gap

One of the persistent frustrations in this field is that adverse events are poorly tracked. A secondary analysis of randomized clinical trials involving spinal manipulation found that only about 38% of published articles reported on adverse events at all. Studies with larger sample sizes, lower risk of bias, and publication dates after 2010 were more likely to include adverse event data.

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This means the overall picture of harm is almost certainly incomplete. When more than six in ten trials do not even mention whether anything went wrong, any estimate of how often serious injuries occur after manipulation should be treated with caution. The denominator is unreliable. The systematic review of adverse events after cervical manipulation also concluded that there is likely under-reporting of cases, making it difficult to draw a clear risk profile.

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The Legal Side

When dissection and stroke do follow chiropractic manipulation, lawsuits can follow. A review of malpractice litigation involving chiropractic spinal manipulation found that the defense won about 71% of cases that went to trial, with the patient prevailing in about 21% of verdicts and the remainder settling. The most common allegation was overly aggressive manipulation, and about two-thirds of cases alleged neurological injury to the spine, the overwhelming majority of which required surgery. Stroke was alleged in about 15% of the cases reviewed.

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A key issue in these cases is informed consent. Patients who were not told about the small but serious risk of vascular injury before manipulation tend to have a stronger legal claim, regardless of whether the manipulation actually caused the dissection. Courts have examined whether standardized consent forms adequately disclose the material risks specific to cervical neck manipulation and whether the practitioner discussed reasonable alternatives before proceeding. For chiropractors, clear documentation that the risks were discussed, however small, is increasingly viewed as a basic professional obligation.

What a Patient Can Reasonably Do

If you are considering cervical spine manipulation, the research does not support the idea that chiropractic adjustments routinely tear healthy arteries. But it also does not rule out that manipulation can worsen an artery already weakened by disease, genetics, or an evolving dissection. Given how rarely these events occur and how poorly the risk factors are characterized, the practical steps are relatively simple.

Tell your chiropractor or therapist about any new or unusual headache, neck pain with an atypical quality, dizziness, visual changes, or family history of connective tissue disorders. These are the flags that might warrant imaging before any manual intervention. If you develop any of these symptoms after a manipulation, treat them as an emergency. The window between an early dissection and a completed stroke can be hours or days, and prompt treatment with blood thinners dramatically improves the odds of a good outcome.

Pre-manipulation positional tests, the kind where the practitioner holds your head turned and asks if you feel dizzy, have been shown to be unreliable and are increasingly considered obsolete in evidence-based practice.

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A careful conversation about your history is more informative. If something does not feel right after treatment, do not wait to see if it resolves on its own.