Scientists questioned the main cause of a common type of stroke

Not blockage, but expansion: scientists have discovered an unexpected cause of one of the most common types of stroke. Researchers from the University of Edinburgh and the UK Dementia Research Institute found that brain arteries literally "balloon out," triggering lacunar stroke. The results of the study have been published in the journal Circulation.

Lacunar stroke accounts for approximately a quarter of all ischemic strokes — conditions in which the brain is deprived of normal blood supply. For decades, the main culprit was considered to be atherosclerosis — the buildup of fatty plaques that narrow the vessel lumen and block blood flow.

However, the new study upends conventional understanding. Scientists have established that the key role in the development of the disease is played not by narrowing, but, on the contrary, by pathological dilation of cerebral arteries — a vascular anomaly in which vessel walls become deformed and lose their normal structure.

The researchers analyzed data from 229 patients who had suffered a lacunar or mild non-lacunar stroke. Each participant underwent MRI, clinical, and cognitive examinations — both during the acute stroke period and one year afterward. The scientists meticulously compared the influence of two factors: narrowing of major arteries due to fatty deposits and pathological dilation of cerebral vessels.

The results proved quite telling. Fatty narrowing of arteries showed no association with either lacunar stroke or small vessel damage. However, patients with dilated arteries had a more than fourfold higher risk of lacunar stroke.

Moreover, vessel dilation correlated with accelerated brain tissue damage and an increased risk of so-called silent strokes — small lesions that develop without noticeable symptoms but gradually erode memory and cognitive functions over time.

According to the study authors, the findings help explain a long-standing mystery: why aspirin and other antiplatelet drugs are often ineffective in preventing lacunar stroke. Scientists are already testing fundamentally new therapeutic approaches as part of the LACI-3 clinical trial, which investigates the effects of drugs targeting the small vessels of the brain directly.