A young woman checked into University Hospital Freiburg in southwestern Germany, complaining of numbness in her arms and signs of a mild stroke. Relying on conventional diagnostic techniques, local physicians soon found that the young woman was suffering from a fairly uncommon condition consisting of a blood clot in the aortic arch, a part of the body’s main artery, the aorta.

The condition was effectively treated with a standard treatment: a simple prescription of a blood-thinning agent, such as aspirin or warfarin. But with the stroke reversed and other symptoms relieved, the young woman no doubt still had questions and concerns about her health. Was this a one-time occurrence, and would there be any further medical consequences? And what had caused this to happen in the first place?