Intracranial atherosclerosis is a buildup of fatty, cholesterol-rich plaque inside the arteries that supply blood to the brain. As plaque accumulates, these arteries narrow, restricting blood flow and raising the risk of stroke. It is one of the most common causes of ischemic stroke worldwide, responsible for 30 to 70% of strokes in Asian, Hispanic, and Black patients and roughly 5 to 10% in White patients.
How Plaque Builds Inside Brain Arteries
The process starts with damage to the inner lining of an artery. High blood pressure, high blood sugar, smoking, and other stressors injure the delicate cells that line the vessel wall. Once that lining is compromised, LDL cholesterol (the “bad” cholesterol) seeps into the artery wall. Immune cells called macrophages rush in to clean up the cholesterol but become engorged with it, turning into what scientists call foam cells. These bloated cells are the building blocks of plaque.
Over time, inflammatory signals cause smooth muscle cells in the artery wall to multiply and migrate toward the plaque, forming a fibrous cap over the fatty core. That cap can be stable for years, gradually narrowing the artery. But if inflammation weakens it, the cap can rupture, triggering a blood clot that blocks the artery entirely. This is how intracranial atherosclerosis causes a stroke: either by slowly choking off blood flow or by suddenly unleashing a clot.
Who Is Most at Risk
Ethnicity plays a striking role. Intracranial atherosclerosis is detected in over 50 to 60% of Asian patients who present with a stroke, compared to fewer than 10% of White patients. Hispanic and Black patients face nearly five times the risk of intracranial-atherosclerosis-related strokes compared to White patients. The reasons are not fully understood but likely involve a combination of genetic predisposition, differences in how the body handles cholesterol, and the distribution of traditional risk factors across populations.
Those traditional risk factors matter regardless of ethnicity. High blood pressure, diabetes, high cholesterol, smoking, and obesity all accelerate plaque growth in brain arteries. Having metabolic syndrome (a cluster of conditions including high blood sugar, high blood pressure, excess abdominal fat, and abnormal cholesterol) alongside diabetes is particularly dangerous. People with both conditions are roughly three times as likely to have multiple areas of significant narrowing in their brain arteries compared to people with neither.
Symptoms and Warning Signs
Intracranial atherosclerosis often produces no symptoms at all until the artery has narrowed enough to starve part of the brain of blood. Imaging studies of people with no neurological complaints find evidence of the disease in roughly 4 to 13% of them. Many people learn they have it only after a stroke or a transient ischemic attack (TIA), sometimes called a “mini-stroke.”
A TIA produces stroke-like symptoms that resolve within minutes to hours. These can include sudden weakness or numbness on one side of the body, slurred speech, trouble understanding others, vision loss in one or both eyes, double vision, dizziness, and loss of balance or coordination. The specific symptoms depend on which brain artery is affected. Some people experience more than one TIA, and the symptoms may differ each time if different areas of the brain are involved. A TIA is a medical emergency because it signals a high risk of a full stroke in the near future.
How It Is Diagnosed
Doctors use imaging to look for narrowing inside the brain’s arteries. The most common initial tests are magnetic resonance angiography (MRA) and CT angiography (CTA), both noninvasive scans that create detailed pictures of blood vessels. Transcranial Doppler ultrasound, which measures blood flow speed through the skull, is another option. Faster-than-normal flow in a particular artery suggests it has narrowed.
These methods show the inside channel of the artery but not the vessel wall itself, so they can miss plaque that hasn’t yet caused significant narrowing. A newer technique called vessel wall MRI can image the artery wall directly, revealing plaque even at earlier stages. Its measurements of narrowing have been shown to closely match those from digital subtraction angiography, the most precise (but invasive) method available.
Narrowing is graded on a scale: less than 30% is considered normal, 30 to 49% is mild, 50 to 69% is moderate, 70 to 99% is severe, and 100% means the artery is completely blocked. Interestingly, arteries can accommodate a surprising amount of plaque before the channel narrows. The threshold at which plaque typically starts producing measurable narrowing is around 55%, meaning the disease can be well established before it shows up on standard imaging.
Treatment With Medication
For most patients, aggressive medical management is the first-line treatment. This approach combines blood-thinning medications, cholesterol-lowering drugs, blood pressure control, and lifestyle changes. Current guidelines from the American Heart Association recommend that patients with 50 to 99% narrowing keep systolic blood pressure below 140 mm Hg, take high-intensity statins, and get at least moderate physical activity regularly. Smoking cessation and management of diabetes are also central to the plan.
After an acute event like a stroke or TIA, patients are typically placed on dual antiplatelet therapy, meaning two blood-thinning medications taken together for a period of time to prevent new clots from forming. This is usually combined with a statin to aggressively lower LDL cholesterol and stabilize existing plaque. Research suggests that driving LDL to very low levels (below 20 mg/dL) may further reduce cardiovascular risk, though the specific benefit for intracranial disease is still being studied.
Even with this intensive approach, the risk remains substantial. Patients who have had a stroke caused by severe narrowing (70 to 99%) face a recurrent stroke risk exceeding 20% within one year. That high recurrence rate is one reason researchers continue looking for better options.
When Stenting Is Considered
A landmark trial called SAMMPRIS compared placing a stent (a small mesh tube) inside the narrowed artery against aggressive medication alone. The results favored medication: the one-year rate of stroke, brain hemorrhage, or death was 20% in the stenting group versus 12.2% in the medication group. Within the first 30 days after treatment, the stenting group had a stroke-or-death rate of 14.7% compared to 5.8% with medication alone. Those findings made aggressive medical therapy the standard of care for most patients.
Stenting has not been abandoned entirely, though. A later study called WEAVE looked at outcomes when the stent was used strictly according to its approved guidelines: patients aged 22 to 80, with 70 to 99% narrowing, who had already suffered at least two strokes in the affected artery’s territory despite being on medication, and who waited at least 8 days after their last stroke before the procedure. Under those strict criteria and with experienced physicians, the complication rate within 72 hours dropped to just 2.6%. That suggests stenting can be safe for a carefully selected group of patients who keep having strokes despite maximum medical treatment.
Living With the Condition
Managing intracranial atherosclerosis is a long-term commitment. The same factors that built the plaque in the first place will keep feeding it if left unchecked. Keeping blood pressure, blood sugar, and cholesterol within target ranges slows progression. Regular physical activity, a heart-healthy diet, and not smoking are not just recommendations but core parts of the treatment plan that have measurable effects on outcomes.
Follow-up imaging is common, particularly in the first year or two after diagnosis, to monitor whether narrowing is stable, improving, or getting worse. Because the posterior circulation (arteries at the back of the brain, supplying areas responsible for balance, vision, and coordination) seems to tolerate more plaque before narrowing occurs, disease in that region may be underdetected and deserves particular attention during monitoring.