A neck adjustment is a high-velocity, low-amplitude thrust applied to the joints of the neck, often producing a distinct popping sound. This manual therapy is a common treatment for neck pain, stiffness, and headaches, typically performed by chiropractors or other trained practitioners. The core concern surrounding this procedure is its potential, though rare, connection to a specific type of stroke. Understanding the anatomy involved and the mechanism of injury provides necessary context for evaluating the actual level of risk associated with this common therapeutic intervention.
Anatomy and the Mechanism of Injury
The possibility of a neck adjustment leading to a stroke involves the major blood vessels that supply the brain through the neck. Four main arteries deliver blood: the two internal carotid arteries, which supply the front portion of the brain, and the two vertebral arteries, which supply the back portion, including the brainstem and cerebellum. The rapid, rotational movement of a neck adjustment is theorized to place sudden, unaccustomed mechanical stress on these vessels.
This stress can potentially cause a cervical artery dissection (CAD), which is a small tear in the inner lining of an artery wall. When the lining tears, blood can enter the wall layers, forming a clot or hematoma. This hematoma can narrow the vessel, impeding blood flow, or a piece of the blood clot can break away and travel to the brain, blocking a smaller artery and resulting in an ischemic stroke.
A vertebral artery dissection (VAD) is most frequently associated with neck manipulation because the vertebral arteries must pass through bony canals in the cervical vertebrae, making them vulnerable to stretching or compression during extreme rotation, especially at the C1-C2 level. A carotid artery dissection (CAD) is less commonly linked to manipulation, as the carotid artery is more mobile but tethered near the upper cervical spine. The resulting stroke from a VAD is known as a vertebrobasilar stroke, which affects the brain regions controlling coordination, balance, and consciousness.
Assessing the True Level of Risk
The risk of a stroke following cervical manipulation is considered low. Some estimates suggest the risk of a serious adverse event, such as a stroke, is as low as 1 in 5.85 million manipulations. Other population-based studies have placed the risk of a stroke for younger adults at about 1.3 cases per 100,000 chiropractic visits, highlighting the event’s rarity.
The scientific community continues to debate whether the adjustment causes the dissection or if the manipulation is merely coincidental to an already developing medical issue. Cervical artery dissection often begins with symptoms like neck pain or headache, which are the very reasons a patient typically seeks a neck adjustment. This situation creates a “protopathic bias,” where the patient’s existing, yet undiagnosed, dissection symptoms lead them to the practitioner, making the subsequent stroke temporally associated with the treatment rather than directly caused by it.
Dissections can also occur spontaneously or from everyday activities, such as turning the head while driving, coughing violently, or engaging in certain sports. However, in individuals with pre-existing vascular fragility, such as those with certain connective tissue disorders, the neck adjustment may act as a trigger that completes the dissection process.
Recognizing Symptoms After a Neck Adjustment
Recognizing the signs of a cervical artery dissection or stroke immediately following a neck adjustment is important for a swift medical response. The most concerning symptom is the sudden onset of a severe headache, often described as a “thunderclap” headache. This symptom may indicate the artery has torn or a blood clot has formed.
Other neurological symptoms that necessitate immediate emergency medical attention include dizziness, vertigo, and nausea that does not resolve quickly. A person may also experience double vision, slurred or difficulty speaking, or sudden loss of coordination and balance. Any new, persistent neurological deficit, such as weakness or sensory loss on one side of the body, should be treated as a medical emergency.
These symptoms can begin immediately after the adjustment or may be delayed by several hours or even days. If any of these symptoms appear, the individual should immediately seek emergency care and inform medical personnel of the recent neck adjustment. Timely intervention is essential, as certain stroke treatments must be administered within a narrow window of time from the onset of symptoms.
Screening and Prevention Strategies
Practitioners utilize several strategies to minimize the risk of a stroke associated with neck adjustments. Patient history focuses on recent trauma, the presence of underlying vascular conditions, or a family history of connective tissue disorders like Marfan or Ehlers-Danlos syndrome. Recent infections, particularly those affecting the upper respiratory tract, are also considered, as they may temporarily increase vascular vulnerability.
While no single clinical test has been shown to reliably predict which specific patient is at risk, open communication is a preventive tool. Practitioners should discuss the potential, albeit rare, risks with the patient to ensure informed consent before proceeding with treatment. For patients who may be at an increased risk, or for those who express concern, practitioners can offer alternative, lower-velocity treatment options, such as joint mobilization, soft tissue therapy, or gentle stretching. These alternatives avoid the high-velocity thrust that places transient stress on the arteries.