Researchers have challenged a fundamental assumption about one of the brain's most common types of stroke, pointing instead to a previously overlooked mechanism that could finally explain why standard treatments keep failing patients.
The discovery centers on lacunar ischemic stroke, which occurs when the brain's smallest blood vessels deteriorate. For years, doctors have assumed this condition stems from fatty plaque accumulating in larger arteries, much like in heart disease. But new evidence from the University of Edinburgh and international collaborators suggests the real problem lies elsewhere: the arteries themselves are enlarging and distorting in abnormal ways.
This distinction matters enormously because it exposes why aspirin and other antiplatelet medications have consistently underperformed as preventive treatments for this stroke type. The drugs were targeting the wrong problem.
To reach these conclusions, researchers tracked 229 patients who had suffered either a lacunar stroke or a mild non-lacunar stroke. Each participant underwent brain imaging scans shortly after their stroke and again a year later. The researchers then compared two competing theories: whether narrowed large arteries or enlarged brain arteries better predicted lacunar stroke and small vessel disease progression.
The results were stark. Narrowing of large arteries showed no meaningful connection to lacunar stroke or to small vessel disease. It did not predict new brain damage on follow-up scans. Artery widening, by contrast, demonstrated a powerful link. Patients with enlarged arteries were more than four times more likely to have experienced a lacunar stroke.
The enlarged arteries also correlated with more aggressive disease progression. Patients showed faster accumulation of brain damage and a higher likelihood of developing silent strokes, small pockets of tissue death that can occur without any noticeable symptoms. More than one in four study participants developed these silent strokes despite receiving conventional preventive medications.
Joanna Wardlaw, a neuroimaging professor at Edinburgh's Institute for Neuroscience and Cardiovascular Disease, emphasized the clinical stakes: "This study provides strong evidence that lacunar stroke is not caused by fatty blockage of larger arteries, but by disease of the small vessels within the brain itself. Recognising this distinction is crucial, because it explains why conventional treatments like antiplatelet drugs are not as effective for this type of stroke and highlights the urgent need to develop new therapies that target the underlying microvascular damage."
The findings are already reshaping treatment strategy. A major trial called LACI-3 is now testing whether drugs such as cilostazol and isosorbide mononitrate can protect the brain's tiny vessels, reduce recurrent strokes, and prevent long-term cognitive and mobility problems that often follow lacunar stroke.
Lacunar stroke ranks among the leading causes of disability and cognitive decline in older adults. It contributes to dementia risk and increases the likelihood of future strokes. Yet despite its prevalence, effective treatments have remained elusive, partly because scientists could not agree on what actually triggers the condition.
The study, published in Circulation, received support from the UK Dementia Research Institute, the Stroke Association, British Heart Foundation, Wellcome Trust, and other national agencies. The research team included collaborators from China and Mexico.
Author Jessica Williams: "This is the kind of finding that should prompt immediate clinical reassessment: if a massive segment of stroke patients have been getting the wrong prevention drugs for years, that's a public health problem waiting to be fixed."
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