The most common type of stroke may have had the wrong cause for decades

Introduction: a medical certainty starts to wobble

The story we've always been told

For decades, medicine told a simple story about stroke: arteries clogging up, fat building up, a clot eventually cutting off blood flow to part of the brain. This story justified entire classes of treatments, from statins to antiplatelet drugs, prescribed to millions of patients worldwide.

A new study published in the journal Circulation is now shaking that certainty for one of the most common types of stroke: lacunar stroke. According to researchers at the University of Edinburgh, the main cause may not be the narrowing of large arteries, but rather the deterioration of much smaller, deeper vessels, whose walls dilate and lose their ability to regulate blood flow.

Why this discovery changes everything

This is not an academic detail confined to specialized journals. If the actual cause of lacunar stroke differs from what was long assumed, then the standard treatments prescribed to thousands of patients every year could be largely ineffective for this specific form of stroke, a conclusion the authors themselves do not hesitate to state plainly.

Lead researcher Joanna Wardlaw, professor of applied neuroimaging at the University of Edinburgh, sums up the significance of the discovery with a candor rarely seen in the scientific world: conventional treatments are not working as expected, and it's time to acknowledge that openly.

What exactly is a lacunar stroke

A quiet but common form of stroke

Lacunar stroke accounts for roughly a quarter of all ischemic strokes, which themselves make up about 87% of all strokes. Unlike more dramatic strokes affecting large arteries, lacunar stroke occurs in the deep, subcortical regions of the brain, often with more subtle symptoms, which does not make it any less dangerous.

This type of stroke is closely tied to what specialists call cerebral small vessel disease, a progressive deterioration of the deep blood vessels of the brain whose exact mechanisms remained unclear for a long time, despite its considerable clinical importance.

Why small vessels were long neglected

Cardiovascular research has historically focused on large arteries, easier to image and more directly linked to heart attacks and massive strokes. The deep small vessels of the brain, by comparison, are technically harder to observe and have therefore received disproportionately little scientific attention relative to their actual role in brain health.

This methodological gap partly explains why it took a study this rigorous, combining magnetic resonance imaging with longitudinal follow-up, to finally isolate the specific role of these vessels in the onset of lacunar stroke.

The Edinburgh study: methodology and scale

A cohort followed over several years

Researcher Joanna Wardlaw's team analyzed data from 229 patients who had suffered a stroke, as part of a cohort called the Mild Stroke Study 3, recruited in Edinburgh between 2018 and 2021. Among these patients, 131 had specifically suffered a lacunar stroke, while the others had experienced a mild non-lacunar form of stroke.

Each participant underwent a series of clinical assessments and a brain magnetic resonance imaging scan at recruitment, then again one year later, allowing researchers to observe the actual evolution of blood vessels over time rather than a single static snapshot of brain condition.

What the researchers precisely measured

The scientists focused on two distinct phenomena: the narrowing of large arteries, long considered the main risk factor for ischemic strokes, and the widening and lengthening of small arteries located deep within the brain, a phenomenon far less studied until now.

This comparative approach made it possible, for the first time with this level of precision, to isolate which of these two mechanisms was truly associated with lacunar stroke and cerebral small vessel disease, rather than simply assuming the two necessarily went hand in hand.

The result that upends everything: widened vessels, not narrowed ones

An association four times stronger than expected

The study's central finding is unambiguous: the narrowing of large arteries was associated with neither lacunar stroke nor any marker of cerebral small vessel disease. By contrast, patients whose scans showed widening and lengthening of the brain's small arteries were four times more likely to have suffered a lacunar stroke.

This association proved strongly correlated with nearly every marker of cerebral small vessel disease measured by the team, a result Joanna Wardlaw calls solid evidence that lacunar stroke is not caused by fatty blockage of large arteries, but by a disease specific to the brain's small vessels themselves.

The "baggy" vessel mechanism

According to the researcher, the widening observed could signal a loss of the normal supporting membranes in the walls of large arteries, making the blood vessels literally more "loose," or "baggy" as she puts it, and therefore less able to properly regulate blood flow. The team believes the same phenomenon affects the much smaller arterioles inside the brain.

This loss of vascular control, rather than simple physical blockage of a pipe by fatty deposits, would explain why damaged small brain vessels struggle to adjust their diameter to the needs of surrounding brain tissue, eventually causing the lesions characteristic of lacunar stroke.

Why current treatments fall short

Drugs designed for a different mechanism

The standard treatments prescribed after an ischemic stroke, such as antiplatelet drugs or aspirin, were designed to prevent clot formation in arteries narrowed by fat buildup. But if lacunar stroke actually results from structural degradation of small vessels, these drugs are simply targeting the wrong mechanism.

This is precisely what Joanna Wardlaw points to when she explains that recognizing this distinction is crucial, since it explains why conventional treatments like antiplatelet drugs are not as effective for this type of stroke, while stressing the urgency of developing new therapies that directly target the underlying microvascular damage.

Limited efficacy acknowledged by the authors themselves

In their conclusions, the study's authors go so far as to write that standard secondary prevention for stroke, including antiplatelet therapy and statins, has limited efficacy in preventing the progression of brain damage related to small vessel disease, while specifying that these approaches remain important and should not be abandoned altogether.

This nuance matters: it's not a claim that current treatments are useless, but that they clearly aren't enough on their own for this specific form of stroke, which justifies the urgent search for new, complementary therapeutic avenues.

The LACI-3 clinical trial: a response underway

Two existing drugs repurposed

Faced with this finding, the Edinburgh team is currently running the LACI-3 clinical trial, testing two drugs already used in cardiology and peripheral vascular medicine: cilostazol and isosorbide mononitrate. According to Wardlaw, these molecules could improve the function of the brain's small blood vessels and thereby better regulate cerebral blood flow.

The trial's ultimate goal is to help prevent more lacunar strokes, as well as cognitive decline and other harmful effects associated with cerebral small vessel disease, a public health issue that extends well beyond the acute stroke episode alone.

A nationwide study in the United Kingdom

The LACI-3 trial is currently running across 38 different centers throughout the United Kingdom, with a recruitment target of 1,300 people who have suffered a lacunar stroke. Participants will follow treatment for 18 months, with cognitive decline as the main outcome measure.

The trial is currently in its first year of recruitment, meaning definitive results likely won't be available for several years, a frustrating but necessary delay to ensure the scientific reliability of future conclusions.

Silent strokes, an underestimated danger

Brain damage without apparent symptoms

The study also revealed that just over a quarter of patients had suffered what researchers call a silent stroke, a small area of brain tissue damage caused by restricted blood flow, but which generally produces no perceptible symptoms. This occurred even in patients receiving standard preventive treatments.

The term "silent" does not mean harmless: these lesions accumulate over time and significantly contribute to long-term cognitive decline, a link increasingly documented by vascular neurology research in recent years.

Increased risk in the year following a first stroke

Patients whose brain vessels showed marked widening also faced a higher risk of suffering a new silent stroke during the year following their initial assessment. This observation reinforces the idea that the underlying vascular deterioration is an ongoing process, not an isolated event resolved once initial treatment is administered.

This continuity of risk justifies, according to the authors, closer monitoring of patients who have suffered a first lacunar stroke, rather than a one-off approach limited to the acute phase following the initial incident.

The study's limitations, a necessary honesty

One city, a limited patient pool

The authors themselves acknowledge an important limitation: all the data come from stroke care services in a single city, Edinburgh. For these results to be generalizable to a broader population, larger studies including patients from several different geographic regions will be needed.

This methodological caution takes nothing away from the solidity of the work done, but it's a reminder that a single study, however rigorous, is never enough on its own to definitively rewrite a medical textbook used for decades worldwide.

A still-hypothetical genetic link

The researchers also raise the possibility of a shared genetic link between artery widening, lacunar stroke, and cerebral small vessel disease, though they cannot definitively confirm this hypothesis with the data currently available. This lead will require further, more in-depth genetic research.

Other explanations, such as additional mechanical stress placed on small vessels by the widening of neighboring arteries, also remain under study, showing that the full mechanism remains only partly understood despite this major advance.

What this means for patients today

Don't stop current treatments

It's essential to clarify that this discovery does not mean patients should abandon their current treatments, such as statins or antiplatelet drugs prescribed by their doctor. These treatments remain relevant for the general prevention of cardiovascular disease, even though their specific efficacy against lacunar stroke is now being questioned.

Any decision about changing treatment must be made in consultation with a medical team, not based on a piece of science journalism, however rigorous its presentation of the facts.

Real hope, but not immediate

For patients who have already suffered a lacunar stroke, this research represents real but not immediate hope: results from the LACI-3 trial won't be known for several years, and no new approved treatment based specifically on this finding is available yet.

This delay, while frustrating for those directly affected, matches the normal and necessary pace of rigorous clinical validation, without which no drug should ever be widely prescribed to the population.

The real toll of stroke on our societies

A leading cause of disability worldwide

Stroke remains one of the leading causes of disability and death worldwide, a burden that affects health systems as much as families confronting the long-term consequences of a stroke, whether major or seemingly minor like lacunar stroke.

The fact that lacunar stroke accounts for roughly a quarter of all ischemic strokes means any improvement in understanding and treating it could have concrete repercussions for the health of millions of people worldwide, well beyond the narrow circle of patients directly studied in Edinburgh.

A societal issue, not just a laboratory one

Beyond the statistics, each lacunar stroke represents a potentially upended life trajectory: loss of independence, progressive cognitive decline, an increased burden on family caregivers. Correctly understanding the true cause of this phenomenon is therefore not merely an academic question, but a societal issue with profound human implications.

It is this human dimension that gives full weight to a discovery that could, eventually, transform how one of the most common types of stroke in the Western world is prevented and treated.

Other parallel avenues of research

A mobilized global scientific community

The Edinburgh team is not alone in studying cerebral small vessel disease. Several research groups around the world are currently exploring complementary approaches, ranging from advanced brain imaging to identifying blood biomarkers capable of detecting this vascular deterioration early, even before a first stroke occurs.

This international scientific mobilization reflects a growing recognition that the brain's small vessels, long neglected in favor of large arteries, deserve research attention proportional to their real role in long-term brain health.

Toward more targeted preventive medicine

Eventually, this new understanding could pave the way for screening tools capable of identifying patients at high risk of lacunar stroke before a first event even occurs, enabling far more targeted prevention than the current general approach based on classic cardiovascular risk factors.

This prospect, while still distant, illustrates how a single well-conducted study can redefine an entire research trajectory for years to come, with potential ripple effects well beyond the initial circle of researchers involved.

What family doctors need to know now

Adjusting the message without spreading panic

For frontline doctors, this research poses a delicate communication challenge: how to incorporate this new knowledge without unnecessarily alarming patients already on treatment, or suggesting a premature abandonment of therapies that retain general preventive value for cardiovascular health.

The best approach, according to several experts consulted in coverage of this study, is to present this discovery as a promising avenue still in development, rather than as a complete and immediate overturning of currently established care protocols.

A call for greater clinical vigilance

This study could nonetheless encourage clinicians to pay closer attention to signs of possible cerebral small vessel disease in their patients, notably through a more careful reading of brain MRI images already taken as part of standard post-stroke follow-up.

This heightened vigilance, without immediately upending established practices, could contribute to earlier detection of at-risk patients, while awaiting the final results of the LACI-3 trial and other similar research currently underway around the world.

What this story teaches us about medicine itself

Science as a process, never as a fixed truth

This discovery illustrates a fundamental reality too often forgotten in public debate about medicine: science is never a definitively established truth, but an ongoing process of questioning, verification, and, sometimes, course correction in the face of new evidence stronger than what came before.

Accepting that treatments prescribed for decades may prove less effective than expected for certain patients is not an admission of medicine's failure, but rather proof of its capacity to self-correct in the face of rigorous, methodologically sound data.

Why scientific patience deserves our trust

In a world saturated with sensationalist announcements of "miracle breakthroughs," this study stands out precisely for its modesty: its authors do not claim to have solved the problem of lacunar stroke, but to have identified a lead solid enough to justify a large-scale clinical trial spanning several years.

This measured approach, far from being disappointing, should instead reassure the public: it is precisely this kind of rigor, without shortcuts or exaggerated promises, that has historically produced the most durable and reliable medical advances.

The role of medical imaging in this breakthrough

Scanners more precise than ever before

This discovery would likely not have been possible without recent advances in magnetic resonance imaging, which now allow unprecedented precision in measuring the diameter and length of small brain arteries, structures once too fine to be analyzed reliably and reproducibly from one patient to another.

This technical advance shows how scientific breakthroughs often depend as much on the tools available as on the ideas themselves: without the ability to properly visualize these vessels, the hypothesis of their central role in lacunar stroke would have remained impossible to rigorously verify.

A standard that could become widespread

If the findings of Joanna Wardlaw and her team are confirmed in larger studies, this kind of detailed imaging of small brain arteries could eventually become standard in the clinical assessment of patients at risk of lacunar stroke, much as imaging of large arteries already is today for more classic strokes.

This potential wider adoption will, however, depend on the availability of specialized equipment and the training of medical staff, two logistical challenges that could slow clinical adoption even if the scientific validity of the approach is confirmed by future research.

Conclusion: a necessary revision, not an instant revolution

What changes right now, and what awaits confirmation

This study does not immediately change everyday clinical practice, but it plants an important milestone in understanding lacunar stroke. It invites researchers, doctors, and the general public to reconsider an assumption taken for granted for decades, without abandoning the therapeutic tools currently available.

The next chapter will be written in the years ahead

The results of the LACI-3 trial, expected in several years, will determine whether the leads pursued by Joanna Wardlaw's team truly translate into new, effective treatments against lacunar stroke. In the meantime, this discovery serves as an essential reminder: even the best-established medical certainties deserve to be regularly tested against the facts.

By Maxime Marquette, columnist

Columnist's transparency note

On the nature of this research

This column is based on a study published in the scientific journal Circulation and on journalistic reporting detailing its methodology, results, and limitations. It is an observational cohort study, not a randomized clinical trial, which calls for particular caution in interpreting its conclusions.

On the limits of this piece

Nothing in this column should be interpreted as individual medical advice. Patients affected by lacunar stroke or cerebral small vessel disease must consult their treating medical team before changing any ongoing treatment, regardless of the information reported in this text.

Sources

Primary sources

ScienceDaily — Study on the true cause of lacunar stroke — July 3, 2026

National Institute on Aging — Research news

American Heart Association — 2026 guideline for the early management of acute ischemic stroke

Secondary sources

Medical News Today — Lacunar stroke linked to widening brain arteries — May 9, 2026

CIDRAP — Center for Infectious Disease Research and Policy

ScienceDaily — Health and medicine news