Researchers have discovered that a common type of stroke is caused by widening of arteries in the brain rather than blockages, contrary to previous understanding, which may explain why standard blood-thinning medications are ineffective.

A study by University of Edinburgh and UK Dementia Research Institute researchers published on Wednesday analyzing 229 patients found lacunar strokes, affecting about 35,000 people annually in the UK, are caused by enlargement and widening of brain arteries rather than fatty blockages, explaining why aspirin and blood thinners are ineffective as treatment.