Neck cracking, defined as any rapid, forceful, or rotational movement of the head that causes a pop or cavitation sound, carries a small but documented risk of causing a stroke. This risk is linked to injury to the neck’s major blood vessels. This rare complication involves the tearing of an artery wall, which can interrupt blood flow to the brain. The following sections explore the anatomical vulnerability and the mechanism by which this injury occurs.
The Arterial Vulnerability in the Cervical Spine
The neck houses four major arteries that supply blood to the brain: the two carotid arteries in the front and the two vertebral arteries in the back. The vertebral arteries are susceptible to injury because they travel upward through bony tunnels within the cervical vertebrae called the transverse foramina.
The arteries are most vulnerable where they curve sharply around the first and second vertebrae (C1 and C2) before entering the skull. This winding path means that extreme or sudden rotation and extension of the neck can cause the artery to stretch, compress, or shear against the surrounding bone. This anatomical arrangement creates a localized weak point where excessive force can initiate an injury.
The Mechanism of Arterial Dissection
The direct cause of a stroke following neck manipulation is arterial dissection, which is a tear in the inner lining of an artery wall. This inner layer, known as the intima, is delicate and can be damaged by sudden, high-velocity movements, particularly rotational forces. When the intima tears, blood enters the space between the layers of the artery wall and begins to pool, forming a hematoma.
This hematoma can expand, either directly blocking blood flow or severely narrowing the vessel, a condition called stenosis. The injury site often causes blood components to aggregate, forming a blood clot (thrombus) on the inner wall of the artery. If a piece of this clot breaks free, it becomes an embolus that travels downstream into the smaller arteries of the brain, causing an ischemic stroke by cutting off the oxygen supply. This process most frequently affects the vertebral artery, leading to a posterior circulation stroke that impacts the brainstem and cerebellum.
Recognizing Symptoms of Vascular Injury
A vascular injury in the neck may produce immediate warning signs, which are often different from the typical symptoms of a stroke. The most concerning symptom is the sudden onset of a severe, unusual headache, frequently described as the “worst headache of their life.” This headache often occurs immediately or within minutes of the neck movement.
Unusual neck pain that is distinct from a typical muscle strain, or persistent pain following the manipulation, is a common initial indicator. Because the vertebral arteries supply the posterior part of the brain, a dissection can quickly lead to symptoms related to balance and coordination. Patients may experience dizziness (vertigo), double vision, slurred speech, or a loss of coordination (ataxia). If any of these symptoms appear after neck movement or manipulation, seeking immediate medical attention is strongly advised, as early detection is important for minimizing neurological damage.
Differentiating Risk Levels and Prevalence
The risk of stroke associated with neck cracking is extremely low, but the context of the movement significantly affects the risk profile. Self-manipulation, where a person cracks their own neck, generally involves less force and is thought to be lower risk than high-velocity, low-amplitude (HVLA) professional manipulation. The popping sound heard during self-cracking is usually cavitation, a harmless release of gas bubbles from the joint fluid.
Even self-cracking is not entirely without risk, especially if underlying arterial disease is present. The statistical rarity of stroke following professional neck manipulation is often cited with wide-ranging estimates, such as one serious adverse event per 50,000 to 6 million adjustments. Studies note that patients under age 45 who have a vertebral artery stroke are more likely to have recently visited a practitioner for neck pain.
It is debated whether the manipulation caused the dissection or whether the patient was already experiencing a dissection-in-progress, which often presents initially as neck pain or headache. Certain risk factors, such as connective tissue disorders like Ehlers-Danlos or Marfan syndrome, can predispose individuals to dissection by weakening the artery walls, making them more vulnerable to minor trauma.