Vertebral artery stenosis is a narrowing of one or both vertebral arteries, the blood vessels that run along the back of your neck and supply blood to the brainstem, cerebellum, and back of the brain. When these arteries narrow significantly, they reduce blood flow to areas that control balance, vision, coordination, and consciousness. About 8% of patients undergoing vascular ultrasound have some degree of vertebral artery narrowing or blockage, and the condition accounts for roughly 25% of all strokes and mini-strokes affecting the back of the brain.
What the Vertebral Arteries Do
You have two vertebral arteries, one on each side, that branch off from the larger arteries beneath your collarbones. They travel upward through small openings in your neck vertebrae, wrap around the top of the spine, and enter the skull, where they merge into a single vessel called the basilar artery. Together, this system feeds the brainstem (which controls breathing, heart rate, and wakefulness), the cerebellum (which coordinates movement and balance), and the occipital lobes (which process vision).
Because these structures handle so many basic functions, even a partial reduction in blood flow can produce a wide range of symptoms. And because the two vertebral arteries merge, a blockage on one side can sometimes reduce flow to the entire system, especially if the other artery is small or also narrowed.
Common Causes
The most frequent cause is atherosclerosis, the same plaque buildup that narrows coronary arteries and carotid arteries. Fatty deposits accumulate in the artery wall, gradually reducing the space blood can flow through. This tends to happen at the very beginning of the artery, where it branches off near the collarbone, though it can occur at any point along the vessel. The same risk factors that drive atherosclerosis elsewhere apply here: high blood pressure, high cholesterol, diabetes, smoking, and aging.
Less commonly, the artery wall can tear (a dissection), which creates a flap of tissue that partially blocks flow. Dissections can happen after neck trauma, chiropractic manipulation, or even sudden head movements, and they tend to affect younger people who don’t have the typical risk profile for atherosclerosis.
Symptoms to Recognize
Many people with mild narrowing have no symptoms at all, particularly if the other vertebral artery compensates. When blood flow drops enough to cause problems, the symptoms reflect the parts of the brain being starved of oxygen:
- Vertigo and dizziness: a spinning sensation or persistent unsteadiness, often the earliest and most common complaint
- Vision changes: double vision, partial vision loss on both sides, or blurring
- Coordination problems: difficulty walking straight, clumsiness, or trouble reaching for objects accurately
- Speech difficulty: slurred or garbled speech
- Numbness: tingling or loss of sensation, sometimes on both sides of the body
- Drop attacks: sudden falls without losing consciousness, caused by a momentary loss of muscle tone
- Loss of consciousness or fainting
- Nausea, headaches, and ringing in the ears
These symptoms can come and go in brief episodes (transient ischemic attacks, or mini-strokes) or arrive suddenly and persist, signaling a full stroke. The highest risk of stroke is in the first month after symptoms begin.
How It Differs From Inner Ear Problems
Because vertigo and dizziness are so common in vertebral artery stenosis, the condition can initially look like a benign inner ear problem such as vestibular neuritis or positional vertigo. A few features help distinguish the two. Inner ear vertigo typically produces horizontal, spinning-type eye movements (nystagmus) that settle down when you focus on a fixed object, and it often comes with nausea, hearing changes, or ringing in the ear. A person with vestibular neuritis can usually stand with their eyes open but becomes very unsteady with eyes closed.
Vertebral artery stenosis and other central causes of vertigo tend to produce nystagmus that doesn’t settle with visual fixation and may be vertical rather than horizontal. There are usually no ear symptoms. Critically, someone with a cerebellar stroke from vertebral artery disease often cannot stand steadily even with their eyes open. Any combination of vertigo with slurred speech, double vision, numbness, or difficulty swallowing points toward a vascular cause rather than an inner ear one.
How It Is Diagnosed
Doppler ultrasound is typically the first test used because it’s noninvasive and widely available. The ultrasound measures how fast blood is moving through the artery. Faster flow at a specific point suggests the artery has narrowed there, like water speeding up through a pinched garden hose. A peak flow speed ratio greater than 2.2 (comparing the narrowed segment to a normal segment) identifies 50% or greater stenosis with about 96% sensitivity and 89% specificity.
If ultrasound findings are concerning, imaging with magnetic resonance angiography (MRA) or CT angiography provides a more detailed picture of where the narrowing is, how severe it is, and whether both arteries are affected. Conventional catheter-based angiography remains the gold standard when precise measurements are needed before a procedure, but it’s invasive and reserved for specific situations.
Treatment With Medication
For most people with vertebral artery stenosis, medical management is the primary treatment. This approach proved so effective in clinical trials that two major randomized studies, the VAST and VIST trials, found stenting offered no clear advantage over medication alone for preventing recurrent strokes.
The medication strategy targets the underlying disease process on multiple fronts. Antiplatelet drugs reduce the risk of blood clots forming on the narrowed artery wall. Statin therapy lowers cholesterol and stabilizes existing plaques so they’re less likely to rupture. Blood pressure control, with a target generally below 140/90 (or below 85 diastolic for people with diabetes), reduces the mechanical stress on artery walls. For people with diabetes, tight blood sugar management is also part of the plan.
Dual antiplatelet therapy, combining low-dose aspirin with a second antiplatelet agent, has been suggested as more effective at preventing clot-related strokes in people with large-artery disease. Blood thinners like warfarin haven’t shown benefit for vertebral artery stenosis specifically, but they are used when the underlying cause is a heart rhythm problem like atrial fibrillation sending clots into the artery.
When Stenting Is Considered
Stenting involves threading a small mesh tube into the narrowed artery to hold it open. Early approaches used balloon angioplasty alone, but this had high rates of re-narrowing, so stents became the standard for procedural treatment. Stenting is generally reserved for people whose symptoms persist or worsen despite optimal medical therapy, or who have severe narrowing on both sides.
After stent placement, dual antiplatelet therapy is continued, typically for at least one month with bare-metal stents and at least one year with drug-coated stents, to prevent clots from forming on the new device.
The decision between ongoing medical management and stenting is individualized. Because the major clinical trials did not show stenting to be superior overall, the procedure is not routine. It remains an option when medication alone isn’t enough to control symptoms or prevent recurrent events.
Long-Term Outlook
People with symptomatic vertebral artery stenosis face a meaningful ongoing risk. The average annual rate of recurrent stroke or similar events is estimated at 10% to 15%, which makes consistent, long-term treatment essential. Risk factor modification, including quitting smoking, managing blood pressure and cholesterol, staying physically active, and controlling blood sugar, forms the foundation of reducing that risk over time.
For the 2024 stroke prevention guidelines, the American Heart Association noted that large-scale data on vertebral artery stenosis remain limited compared to carotid artery disease, and comprehensive evidence-based recommendations specific to vertebral stenosis are still developing. In practice, the same principles that protect against atherosclerosis elsewhere apply: control the risk factors aggressively, use antiplatelet and statin therapy as directed, and monitor for any new or worsening symptoms that could signal a change in blood flow.