Stroke Timing and Vertebral Artery Dissection: What the Window Suggests

Cervical chiropractic manipulation remains linked with the potential for vertebral artery dissection (VAD) and stroke in the minds of many consumers, medical professionals, and attorneys. The common, unfortunate assumption: a patient receives a cervical adjustment, later suffers a stroke, and the adjustment is presumed to have caused the vascular injury.

As chiropractors know, several major studies have failed to establish a clear causal relationship between chiropractic manipulation and VAD or stroke.¹ The population-based Cassidy study found no excess risk of vertebrobasilar stroke associated with chiropractic care compared with primary care and concluded that the association was likely explained by patients with headache and neck pain from an evolving dissection seeking care before their stroke.⁵ A more recent study by Whedon, et al., found no clinically significant differences in risk of vertebrobasilar stroke between older adults seeing a chiropractic versus a medical physician.⁸

Work by Herzog and colleagues found that cervical manipulation did not place undue strain on the vertebral artery and did not appear to be a factor in vertebrobasilar injuries.⁷ And the extensive literature review by Haldeman, Kohlbeck and McGregor could not identify a specific neck movement, trauma or type of manipulation as the offending event in the majority of reported cases.⁶

So, why does that association exist?

The Patient May Already Have a Developing VAD

VAD does not necessarily announce itself with a stroke. Early symptoms can include neck pain and headache – symptoms that are common, nonspecific and easily mistaken for an ordinary musculoskeletal problem.²

That is particularly important for chiropractors.

A 2024 systematic review and meta-analysis examined patients with VAD who presented to chiropractors. It found that neck pain and headache were prominent presenting symptoms and concluded that patients with evolving VAD may inadvertently seek chiropractic care because of those symptoms, potentially confounding the association between cervical manipulation and VAD.³

This creates a very different possible sequence of events:

VAD begins → neck pain / headache develops → patient seeks chiropractic care → manipulation occurs → stroke develops later.

If that is what happened, the manipulation occurred after the clinical process had already begun, and the developing vascular event may have been what brought the patient to the chiropractor.

The Clock May Already Be Running

A cervical artery dissection can precede the ischemic stroke by days. A large 2017 study published in Stroke examined 2,791 patients who had a cervical artery dissection without stroke or TIA at the time of diagnosis. The increased risk of stroke was concentrated in the first two weeks following the dissection, with a much smaller increase during weeks three and four and no statistically significant increase during the remainder of the 12-week observation period.⁴

That finding matters because it gives us a clinically meaningful clock. The clock begins with the beginning of the dissection – not necessarily with the chiropractic adjustment.

If a patient develops new neck pain or headache, seeks chiropractic care several days later, receives manipulation, and then suffers a stroke within the expected post-dissection period, the manipulation should not automatically be assumed to have initiated the vascular event. The vascular process may already have been underway.

Raising a New Question

This is where a growing body of case-report literature becomes particularly interesting. When cases document the sequence of symptoms first, chiropractic care second, stroke later, the timing becomes more than a footnote. It becomes a potential clue to what actually happened. If the patient's characteristic VAD symptoms began before manipulation, the dissection may have preceded the chiropractic treatment.

That is fundamentally different from a scenario in which a patient undergoes manipulation without preceding symptoms, experiences a new onset of significant symptoms immediately afterward, and subsequently develops a stroke. Those two timelines should not automatically be treated as equivalent. And yet, in many discussions of chiropractic and stroke, they effectively are.

Why This Distinction Matters

For an unsuspecting consumer, medical doctor or attorney, the sequence may appear obvious: “I had my neck adjusted and then had a stroke.” A physician encountering the case after the fact may see the same temporal relationship. And in a legal proceeding, the fact that treatment preceded the stroke can become a particularly powerful narrative.

But a chronological reconstruction can tell a very different story. What happened first: the manipulation or symptoms associated with VAD? If the patient had new neck pain or headache before seeking care, the relevant vascular process may have already started. The subsequent stroke may then fall within the expected period of elevated stroke risk following the dissection.⁴

In that circumstance, the chiropractic visit may be temporally associated with the stroke without being the cause of the underlying vascular injury. That interpretation is consistent with the Cassidy population study, which found no excess risk from chiropractic care compared with primary care and concluded that patients with headache and neck pain from VAD were likely seeking care before their stroke.⁵

What Should Researchers Be Looking at Next?

The next step may be surprisingly simple. Rather than asking only whether a patient received cervical manipulation before a stroke, researchers should carefully reconstruct the entire timeline:

• When did the neck pain or headache begin?
• When did the patient seek care?
• When was cervical manipulation performed?
• When did neurological symptoms or stroke occur?

That chronology could help distinguish two very different possibilities: manipulation → new vascular injury → stroke; versus vascular injury → neck pain/headache → chiropractic visit → stroke. The second sequence is not merely theoretical. The known presentation of VAD and the timing of stroke following dissection make it biologically and clinically plausible.^2-4

It is possible that a significant proportion of cases traditionally attributed to manipulation actually follow the second sequence. In fact, I’d like to encourage the research community to consider a retrospective study, as I suspect it would show that all the cases attributed to manipulation may follow the second sequence. In cases I’ve handled:

• The chiropractor’s file identifies the date that headache and/or neck pain begins.
• MR and CT imaging provide objective evidence that the dissection preceded CMT and matches the date of the onset of symptoms. (The appropriate imaging was done in every case I’ve handled.).
• The date of the stroke is typically 7-14 days following the dissection and has never been beyond 30 days.

It also seems reasonable that if CMT caused dissections leading to stroke, the incidence of these events would be distributed over the entire course of chiropractic treatment - not within the first few days / weeks.

None of this eliminates the importance of appropriate clinical evaluation when a patient presents with unusual, severe or changing symptoms. But it does mean that a stroke occurring after chiropractic care is not, by itself, evidence that chiropractic care caused the dissection. The existing evidence, including population research, biomechanical testing and systematic review, does not establish a causal relationship.^{1, 5-7} That possibility deserves much more attention in future research – and in the clinical and legal interpretation of cases involving chiropractic care.

References

1. 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.
2. Haynes MJ, Vincent K, Fischhoff C, Bremner AP, Lanlo O, Hankey GJ. Assessing the risk of stroke from neck manipulation: a systematic review. Int J Clin Pract, 2012;66(10):940-947.
3. Trager RJ, Troutner A, Pikus HJ, et al. Symptoms of patients with vertebral artery dissection presenting to chiropractors: a systematic review and meta-analysis. Cureus, 2023;15(12):e51297.
4. Morris NA, Merkler AE, Gialdini G, Kamel H. Timing of incident stroke risk following cervical artery dissection presenting without ischemia. Stroke, 2017;48(3):551-555.
5. Cassidy JD, Boyle E, Côté 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.
6. Haldeman S, Kohlbeck FJ, McGregor M. Risk factors and precipitating neck movements causing vertebrobasilar artery dissection after cervical trauma and spinal manipulation. Spine, 1999;24(8):785-794.
7. Herzog W, Leonard TR, Symons B, Tang C, Wuest S. Vertebral artery strains during high-speed, low amplitude cervical spinal manipulation. J Electromyograph Kinesiol, 2012;22:740-746.
8. Whedon JM, et al. Risk of stroke after chiropractic spinal manipulation in Medicare B beneficiaries aged 66 to 99 years with neck pain. J Manipulative Physiol Ther, 2015 Feb;38(2):93-101.