Illustration of cerebral blood vessels with a focus on flow and time.

Brain Blood Flow: Why Timing Matters More Than Stenosis in Carotid Artery Disease

Rhea Morgan in Health & Wellness December 2025 • 4 min read.

"New research suggests that how quickly blood flows through the brain is a better indicator of stroke risk than the degree of artery blockage itself."

For people at risk of stroke due to narrowed carotid arteries (carotid stenosis), the big question is always: what's the real risk? Current guidelines for treatment, like surgery or stenting, largely focus on how blocked the artery is. If it's blocked enough, intervention is recommended.

But the story might be more complex than that. Think of it like rush hour on a highway. A lane closure (stenosis) always slows things down, but sometimes traffic still flows reasonably well, and sometimes it's a complete standstill. The key difference? Blood flow.

Now, a new study is challenging the traditional focus on artery blockage alone, and the research suggests that the speed of blood flow in the brain is a better indicator of stroke risk than the degree of blockage in the carotid arteries.

Cerebral Circulation Time: A Better Way to Gauge Stroke Risk?

Illustration of cerebral blood vessels with a focus on flow and time.

Researchers in Taiwan investigated a better way to assess stroke risk in people with carotid stenosis. Instead of just looking at how blocked the carotid artery was, they measured something called 'cerebral circulation time' (CCT).

CCT is essentially how long it takes blood to travel from a major artery in the neck to a vein in the brain. The researchers used a special type of X-ray imaging (DSA) to precisely measure this travel time.

They then compared CCT to other factors known to affect stroke risk, like: The degree of carotid artery narrowing. The presence of collateral blood vessels (detours the brain makes to get blood around the blockage). Whether the person had already experienced stroke symptoms (a warning sign).

The surprising finding? CCT was more strongly linked to stroke symptoms than the degree of stenosis itself. In other words, people with slower blood flow (longer CCT) were more likely to have experienced stroke-like symptoms, regardless of how blocked their artery was. This suggests that how quickly blood is getting to the brain matters more than the narrowing alone.

What This Means for You

These findings suggest that doctors may need to look beyond just the degree of stenosis when assessing stroke risk in carotid artery disease. Cerebral circulation time, or CCT, could be a valuable additional tool.

For people with carotid stenosis, it emphasizes the importance of optimizing overall cardiovascular health. Things that improve blood flow—like managing blood pressure, cholesterol, and blood sugar—may be even more critical than previously thought.

While more research is needed, this study highlights that the speed of blood flow to the brain is a key factor in stroke prevention. So, if you're at risk, talk to your doctor about a comprehensive assessment that includes looking at circulation time, not just artery blockage.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1136/neurintsurg-2017-013293, Alternate LINK

Title: Prolonged Cerebral Circulation Time Is More Associated With Symptomatic Carotid Stenosis Than Stenosis Degree Or Collateral Circulation

Subject: Neurology (clinical)

Journal: Journal of NeuroInterventional Surgery

Publisher: BMJ

Authors: Yong-Sin Hu, Wan-Yuo Guo, I-Hui Lee, Feng-Chi Chang, Chung-Jung Lin, Chun-Jen Lin, Chao-Bao Luo, Chih-Chun Wu, Han-Jui Lee

Published: 2017-08-30

Everything You Need To Know

What is Cerebral Circulation Time (CCT) and why is it important?

Cerebral circulation time (CCT) measures the time it takes for blood to travel from a major neck artery to a brain vein. This is significant because the study found that CCT is a stronger indicator of stroke risk than the degree of carotid artery narrowing. A longer CCT indicates slower blood flow, which is associated with a higher likelihood of stroke-like symptoms, irrespective of the extent of carotid stenosis. This implies that focusing solely on the degree of carotid artery blockage may not accurately predict stroke risk.

What is Carotid Stenosis and why is it a factor?

Carotid stenosis refers to the narrowing of the carotid arteries, which are major blood vessels in the neck that supply blood to the brain. In the context of stroke risk, the degree of carotid stenosis has traditionally been a primary factor in determining the need for interventions like surgery or stenting. However, this is being challenged by new findings that suggest the speed of blood flow is more critical than the degree of blockage. This impacts patients because those with significant stenosis might not necessarily be at high risk if their blood flow is adequate, as indicated by a normal cerebral circulation time.

How is Cerebral Circulation Time (CCT) measured?

Cerebral circulation time (CCT) is assessed using a special X-ray imaging technique called DSA (Digital Subtraction Angiography). DSA allows for precise measurement of how long it takes blood to travel from a major artery in the neck to a vein in the brain. This is crucial because a longer CCT suggests slower blood flow, which is linked to increased stroke risk. By measuring CCT, doctors can gain a more accurate understanding of the brain's blood supply and assess stroke risk more effectively.

What are collateral blood vessels, and how do they play a role?

Collateral blood vessels are alternative pathways that the brain can use to reroute blood flow around a blockage in a major artery, such as the carotid artery. Their presence is one of the factors that were compared to CCT in the study. The existence of collaterals can help maintain adequate blood flow to the brain even when there is carotid stenosis. However, CCT was found to be a more critical indicator of stroke risk, suggesting that the speed of blood flow remains a key factor, regardless of the presence of these detours.

What are the implications of these findings on treatment?

The findings suggest that the speed of blood flow in the brain, measured by cerebral circulation time (CCT), is more strongly linked to stroke symptoms than the degree of carotid artery narrowing (stenosis). This means that doctors may need to consider CCT as a valuable additional tool when assessing stroke risk in patients with carotid artery disease. This could lead to more personalized treatment plans based on individual blood flow dynamics, potentially preventing unnecessary interventions for patients with good blood flow and prioritizing interventions for those with reduced cerebral circulation time, regardless of the degree of carotid stenosis.