Shedding More Light On Cryptogenic Stroke

When it comes to stroke, the more we know, the better. Knowing what caused a stroke may shake us out of our habits and comfort zones, empowering us to do something about it. Unfortunately, in about a third of ischemic strokes, doctors cannot help empower their patients because a cause hasn’t been determined. Unexplained ischemic strokes — what doctors call cryptogenic strokes — are, by their nature, disquieting.

In the first article in our two-part series on unexplained stroke, we discussed atrial fibrillation and patent foramen ovale — two common heart malfunctions — as potential sources of mystery clots. In this second installment, we will look at two other possible sources: non-stenotic plaques and hypercoagulable states.

Non-Stenotic Plaques

Plaque is a buildup of cholesterol and other substances inside the wall of blood vessels. After years, plaque can become calcified and hard and continued buildup can lead to the narrowing of blood vessels. Stenosis means narrowing.

So non-stenotic plaques don’t cause arteries to narrow. However, part of the plaque may break off, travelling through the bloodstream, possibly blocking an artery and causing a stroke.

Hooman Kamel, assistant professor of neurology at Weill Cornell Medical College at Cornell University, explained that doctors are becoming increasingly aware that these plaques pose a risk. “We’re starting to use more advanced imaging techniques to be able to find those,” he said. “In fact, we just had a scientific paper recently that suggested that at least some portion of cryptogenic strokes are due to non-stenotic plaques.”

Hypercoagulable States

Hypercoagulable states refers to blood that clots abnormally. According to Kamel, awareness of these states started with blood specialists who realized that some patients who kept getting blood clots had certain genetic abnormalities or underlying diseases that made it easier for their blood to spontaneously form clots. Stroke neurologists thought that same mechanism might partly explain why people were having strokes. “We specifically look for that in young patients, like a 40-year-old who otherwise seems healthy but suddenly has a stroke,” Kamel said.

For every 100 cryptogenic stroke patients who receive the blood and genetic tests necessary, only a handful — the low single digits — will have hypercoagulable blood. These are so rare that there aren’t great studies available to guide doctors on who should be tested and what treatment they should receive. “In general, in a young patient who has no other apparent cause of stroke and who has a positive test for one of these hypercoagulable conditions, I think a lot of doctors would consider putting them on an anticoagulant like warfarin rather than using the standard medicines like aspirin that we commonly use after a stroke,” Kamel said. “I don’t think it’s going to end up explaining the bulk of cryptogenic strokes, at least not according to the tests we have available now.”

Not Knowing ≠ Doing Nothing

Just because a cause isn’t identified doesn’t mean there aren’t steps to be taken to prevent another stroke. Anyone with cryptogenic stroke should do all the things recommended to reduce stroke risk — quit smoking, control high blood pressure, reduce cholesterol and blood sugar, lose weight, eat better and be physically active. “I often refer patients to Life’s Simple 7,” Kamel said. “It’s a very simple but powerful way of getting at all the major risk factors for cardiovascular disease. They are very good guidelines for anyone to follow but especially someone who’s had a stroke because they are at a higher risk for having another one than the average person.” Kamel particularly emphasizes the importance of controlling blood pressure. “I think we’re realizing more and more that patients will often need two, three, even four medications to get their blood pressure under adequate control,” he said.

There have been numerous advances in the past few years, so anyone who has had an unexplained stroke would probably benefit from visiting their doctor again. “They could certainly benefit from a prolonged period of heart rhythm monitoring to rule out underlying AFib,” Kamel said.

In the past, most stroke patients would have undergone imaging of their carotid and vertebral arteries to see if they were narrowed due to atherosclerosis, but imaging of intracranial arteries has made advances more recently. “The imaging of these arteries is very important, and certainly, someone who’s had an unexplained stroke and never had that type of imaging, I think, could benefit from that,” Kamel said.

Another change in stroke care is the implementation of a team approach, with the primary care physician playing the role of quarterback. “Healthcare systems are moving toward a team-based approach where you have physicians and nurses and pharmacists working with patients to address all these different factors,” Kamel said. “I think that kind of care can be of great benefit for cryptogenic stroke patients.”

Finally, Kamel urges patients to check in with their doctors. “The highest risk period for having a second stroke is in the first few months,” he said. “We are very careful about closely following up within weeks to make sure that everything is going well. Once the appropriate medicines have been started, the right lifestyle changes have been instituted, and the patients are further out from their stroke, I think just checking in every three to six months with their physicians is probably fine.”

Find out more about cryptogenic stroke. Download What’s at the heart of my cryptogenic stroke? A patient guide to strokes of unknown cause and see our Fall 2015 issue of Stroke Connection for the first part of this two-part series.

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