Heart Shunts, Migraine, and Stroke: What a 10-Year Study of 1,215 Patients Found

Why This Study Was Done

A right-to-left shunt is a path that lets some blood skip the lungs and pass straight from the right side of the circulation to the left. The most common cause is a patent foramen ovale (PFO), a small flap-like opening between the upper chambers of the heart that everyone has before birth and that stays partly open in many adults. Most people with a PFO never know they have one.

Shunts come up often in migraine care because they are found more often in people with migraine with aura, and because a shunt can, in theory, let a small clot from the veins reach the brain. Many people with aura have had a "bubble study" after a scan or a neurologic symptom, and then face a hard question: is this shunt a real stroke risk for me, or an incidental finding?

Earlier research mostly compared groups and gave average risks. A team in China set out to build a simple score, using details already known at the first visit, that could sort people with migraine and a confirmed shunt into lower and higher long-term stroke risk. The study was published in Cephalalgia. If you want background on aura itself, our guide to migraine phases and timeline explains where aura fits in an attack.

How the Study Was Done

This was a long-term cohort study. Everyone had migraine and a right-to-left shunt confirmed by contrast-enhanced transcranial Doppler, a bubble test in which tiny air bubbles are injected into an arm vein while ultrasound listens for bubbles reaching the arteries of the brain. The outcome was cryptogenic ischemic stroke, meaning a stroke caused by a blocked artery where the usual workup finds no other explanation.

The researchers used a Cox regression model to find which baseline features predicted stroke, then turned those features into integer points. They tested the score in the development group, repeated the check with five-fold cross-validation, and then ran it on the external group.

The Migraine Risk Stratification Score

Four features predicted stroke independently. The researchers named the result the Migraine Risk Stratification Score (MRSS).

A total of 0 to 4 points was classed as low risk and 5 to 7 points as high risk.

In bubble-test reports, a "permanent" shunt usually means bubbles cross at rest, not only during a strain maneuver, and "large" refers to how many bubbles get through. Shunt size and pattern are written on the report, so your clinician can tell you which category applies to you.

Reaching 5 points takes either all three 2-point features, or two of them plus age 50 or older. A 40-year-old with aura and a large shunt, for example, scores 4 points and still falls in the low-risk group.

What the Study Found

People in the high-risk group had a much higher rate of cryptogenic ischemic stroke over 10 years than people in the low-risk group.

A hazard ratio of 5.06 means the high-risk group had about five times the rate of stroke over time. The 95% confidence interval of 3.31 to 7.74 stays well above 1, so the gap is unlikely to be chance alone. Kaplan-Meier curves showed the two groups pulling apart over the decade of follow-up.

How Well the Score Separated the Groups

The researchers measured discrimination with the area under the curve (AUC). An AUC of 0.5 is a coin flip and 1.0 is perfect sorting.

The 3-year external value was based on only five strokes, so the authors advise caution with it.

Values in the mid-0.7 range are usually described as fair to good. The higher external values look encouraging, but the external group was small and had few events, so those numbers are less stable than the development numbers.

Reading the Numbers

The most useful part of the score is what it says about people who land in the low-risk group. Across time points, its negative predictive value was 0.96 to 0.99. In plain terms, when the score called someone low risk, that person was very likely to stay free of this type of stroke.

The positive predictive value was much lower, 0.05 to 0.19. That means most people labeled high risk did not have a stroke during the period measured. You can see the same thing in the 10-year figure: even in the high-risk group, roughly 78 out of 100 people stayed stroke-free.

That is why the authors describe the MRSS as a rule-out tool for baseline risk sorting, not a precise personal risk estimate and not a guide to choosing treatment.

Limitations to Keep in Mind

The authors state plainly that the score needs prospective validation and recalibration before routine use. Several other points shape how far the findings travel.

• Everyone already had a confirmed shunt. These numbers do not apply to people with migraine in general, or to people with aura who have never had a bubble test.
• The cohorts came from Chinese hospital centers. Stroke rates, referral patterns, and how shunts are found and treated differ across countries and health systems.
• The external group was small. With 237 people and few early strokes, its accuracy estimates are imprecise.
• Prediction does not show cause. A feature that predicts stroke in this model is not proof that the feature causes stroke, and the score does not test whether closing a shunt or taking a medicine changes the risk.
• Stroke type matters. The outcome was cryptogenic ischemic stroke, not every kind of stroke, so the score says nothing about strokes with a known cause such as atrial fibrillation or narrowed arteries.

Treatment during follow-up, such as shunt closure or blood thinners, could also have changed stroke rates in either group.

What This Means for People With Migraine

If you have migraine with aura and a bubble test showed a shunt, this study gives you and your clinicians a clearer way to talk about risk. If your age, aura status, and shunt features put you in the low-risk range, the data suggest your 10-year chance of a cryptogenic stroke is small. If you land in the high-risk range, that is a reason for a careful conversation with a neurologist and a cardiologist, not a reason for alarm.

Decisions about shunt closure or long-term blood thinners depend on much more than this score, including whether you have already had a stroke or transient ischemic attack, your other vascular risks, and bleeding risk. A trial we covered earlier compared a blood thinner with a beta blocker for migraine prevention in people with a PFO; you can read our summary of that PFO trial for the migraine side of the question.

The risk factors you can change still carry most of the weight. Blood pressure, smoking, diabetes, and cholesterol drive a large share of strokes in everyone, and our overview of stroke prevention in people with migraine walks through the practical steps. For the broader picture of how migraine relates to heart and blood vessel health, see the migraine and cardiovascular connection.

For women, risk also shifts across the life course. Our recent article on migraine, heart attack, and stroke before and after menopause covers a 2.2 million-woman study. To bring your aura history, bubble test results, and medicine list to your next visit in one place, use our printable migraine appointment summary sheet.

Key Takeaways