Atherosclerosis is a process in which plaque (comprising cholesterol and other substances) accumulates within—and can lead to narrowing of—the blood vessel wall. When a fragment of the plaque breaks off of the wall, it can be carried through the blood towards the brain. This fragment can cause a blockage—depriving the brain of oxygen and causing an ischemic stroke.
To assess whether atherosclerosis is the cause of a stroke, doctors use an imaging technique called CT angiography to visualize blood vessels in the head and neck. The traditional thinking has been that only those plaques that significantly narrow the blood vessels cause strokes.
However, one in four people who have suffered an ischemic stroke have neither significant narrowing of blood vessels nor evidence of other causes. These strokes are classified as ‘cryptogenic’, meaning that there is no identifiable reason for the stroke. Without this information, it is difficult for stroke survivors to know which treatment options are best to prevent recurrence.
Krembil Clinician Investigator Dr. Daniel Mandell initiated a study to address this gap in knowledge. His research team used CT angiography to examine the vessels of those with cryptogenic stroke; however, instead of looking for vessel narrowing as is routinely done, they looked directly at the vessel wall to identify plaques in the absence of narrowing.
They found a striking number of large plaques in the blood vessels supplying the brain of those with cryptogenic stroke. This suggests that plaque accumulation may be a causative factor in cryptogenic strokes, despite the fact that these plaques were not causing significant narrowing and not considered clinically relevant, until now.
“CT angiography is a widely available imaging technique. Doctors interpreting these images usually look for blood vessel narrowing but don’t attempt to directly visualize plaques,” says Dr. Mandell. “Our study suggests that it is possible to measure the plaque itself. Interpreting images in this way may improve our ability to identify the cause of strokes.”
This work was supported by The Netherlands Organisation for Scientific Research, the Dutch Thrombosis Society, the Remmert Adriaan Laan Foundation, the Association of University Radiologists and the Toronto General & Western Hospital Foundation.
Nonstenotic carotid plaque on CT angiography in patients with cryptogenic stroke. Coutinho JM, Derkatch S, Potvin AR, Tomlinson G, Kiehl TR, Silver FL, Mandell DM. Neurology. doi 10.1212/WNL.0000000000002978. 2016 Jul 13. [Pubmed abstract]