Basilar artery stenosis is a narrowing of the basilar artery, the main blood vessel at the back of your brain. This artery feeds oxygen-rich blood to your brainstem, cerebellum, and the visual processing areas of your brain. When it narrows, these critical structures receive less blood flow, raising your risk for transient ischemic attacks (TIAs) and stroke.
What the Basilar Artery Does
The basilar artery sits at the base of your skull and supplies three areas you depend on constantly. Your brainstem controls heart rate, breathing, and sleep. Your cerebellum coordinates movement, speech, and balance. And your occipital lobes process everything you see. A narrowed basilar artery threatens all of these functions simultaneously, which is why even partial blockages can produce a wide range of neurological symptoms.
Causes and Risk Factors
Atherosclerosis, the gradual buildup of fatty plaque inside artery walls, is the primary cause. The same process that narrows heart arteries can narrow the basilar artery over years or decades. The condition is twice as common in men as in women and typically appears in older adults, though certain risk factors can push onset earlier: diabetes, high blood pressure, obesity, high cholesterol, smoking, and a sedentary lifestyle.
Less commonly, the artery can narrow from inflammation of the vessel wall or from a tear in its lining (dissection), but atherosclerosis accounts for the vast majority of cases.
Symptoms to Recognize
Early symptoms are often frustratingly vague. Dizziness and blurry vision are common first signs, which makes the condition easy to dismiss or misattribute to other causes. As the narrowing progresses, symptoms become more clearly neurological:
- Motor weakness: one-sided or even all-four-limb weakness, sometimes described as “herald hemiparesis” when it comes and goes as a warning sign before permanent damage
- Speech problems: slurred or difficult-to-understand speech
- Vision changes: double vision or loss of vision
- Coordination loss: unsteady gait, difficulty with balance
- Swallowing difficulty and facial weakness: seen in more than 40% of patients with significant blockage
- Nausea, vomiting, headache, or neck pain
An altered level of consciousness and focal motor weakness are considered the hallmark signs. If the artery becomes fully blocked, the situation is a medical emergency with high mortality.
How It Is Diagnosed
Doctors use imaging to see the artery and measure how narrow it has become. The gold standard is digital subtraction angiography (DSA), an X-ray technique that provides a detailed picture of blood flow through the artery. For a less invasive first look, transcranial ultrasound can estimate the degree of narrowing by measuring how fast blood moves through the vessel. Faster flow at the narrowed point indicates more severe stenosis.
CT angiography and MR angiography are also commonly used, offering detailed images without the invasiveness of traditional angiography. Stenosis is graded by the percentage of the artery’s diameter that is blocked. The categories that matter clinically are under 50%, 50 to 69%, and 70 to 99%. Patients with 80% or greater narrowing face the highest rates of recurrent stroke and death, with most of those events concentrated in the first six months after symptoms appear.
Treatment: Medications Come First
For most patients, the frontline treatment is aggressive medical management rather than surgery. This typically involves dual antiplatelet therapy (two blood-thinning medications working together), tight blood pressure control, cholesterol-lowering medication, and lifestyle changes targeting the underlying atherosclerosis.
A landmark trial published in the New England Journal of Medicine settled a major debate in this field. The SAMMPRIS trial compared aggressive medical therapy alone against medical therapy plus stenting (placing a small metal tube inside the artery to hold it open) in patients with 70 to 99% narrowing. The results were decisive: stenting was worse. Within 30 days, 14.7% of stented patients had a stroke or died, compared to 5.8% in the medication-only group. At one year, the gap persisted, with stroke or death occurring in 20% of stented patients versus 12.2% of those on medications alone. The trial was stopped early because the difference was so clear.
Because of these findings, stenting is now reserved for patients who continue to have TIAs or strokes despite optimal medical therapy. In those refractory cases, endovascular treatment may be considered as a last resort, performed under local anesthesia after pretreatment with antiplatelet medications.
What Happens if the Artery Fully Blocks
Complete basilar artery occlusion is one of the most dangerous types of stroke. In a cohort study with up to 20 years of follow-up, three-month mortality after full occlusion was 39.6%, with 89% of those deaths occurring in the first month. Only about 30% of patients achieved a good functional outcome at three months.
The picture for survivors, however, is more encouraging. Among those who made it past the three-month mark, the median follow-up was nearly nine years. These survivors showed relative longevity, though cardiac disease and other vascular problems became increasingly important causes of illness over time. This underscores why managing the underlying atherosclerosis, not just the basilar artery itself, is critical for long-term survival.
Living With Basilar Artery Stenosis
If you’ve been diagnosed, the most impactful things you can do relate to the risk factors driving the plaque buildup. Keeping blood pressure and cholesterol within target ranges, managing diabetes carefully, quitting smoking, and staying physically active all slow the progression of atherosclerosis throughout your body, including in the basilar artery. Patients with severe stenosis (80% or greater) need especially close monitoring in the first six months, when the risk of a major event is highest. After that initial high-risk window, the rate of complications drops, though ongoing medical management remains important indefinitely.