A mystery: Understanding cryptogenic stroke

When a person experiences a stroke, the type of treatment he or she receives is largely dependent on what caused the stroke. So what happens when the cause is unknown?

Treatment following a stroke has dual purposes — it’s intended to limit the damage caused by the stroke and help prevent another stroke. Because of this, stroke patients undergo different types of testing to determine the cause of their stroke.

But in a fairly large number of cases, the stroke has no known cause, a type of stroke known as “cryptogenic stroke.” In fact, according to the American Heart Association (AHA)/American Stroke Association (ASA), as many as 30 percent of ischemic strokes are classified as cryptogenic.

Ruchir Shah, MD, a board-certified neurologist and vascular neurologist with UT Erlanger Neurology, offers answers to some questions about cryptogenic strokes.

Q: So, what exactly is a cryptogenic stroke?

A: In most cases, a stroke is caused by a blood clot that blocks the blood flow to the brain. In some instances, despite testing, the cause of a stroke can’t be determined. In this case, the stroke of unknown cause is called a “cryptogenic stroke”.

Because approximately 1 in 4 stroke survivors will likely have another stroke event, finding the cause of stroke will help your physician treat the underlying cause of your stroke and minimize the likelihood of another event.

Q: What are potential causes behind a cryptogenic stroke?

A: There are many different causes, ranging from infection to genetic blood clotting disorders to atrial fibrillation.

Atrial fibrillation, or AFib, is a fairly common condition in the United States, affecting nearly 3 million Americans. If a person has this condition, the upper chambers of the heart beat rapidly and irregularly and blood doesn’t pump efficiently to the rest of the body. Atrial fibrillation is one of the potential causes of cryptogenic stroke — increasing risk of stroke five times. AFib can go undetected because it often has no symptoms and may occur infrequently.

Other causes for cryptogenic stroke include Patent Foreman Ovale (PFO), inherited thrombophilias, and infectious, autoimmune and inflammatory states.

Q: What types of testing are done to try and uncover the cause of a stroke?

A: When a person experiences a stroke, it’s important to be seen quickly by neurologists who specialize in stroke.

We conduct a thorough workup to find the underlying cause. To help determine the cause, we typically use a combination of blood work, imaging tests such as CT scans and MRIs, and transthoracic echocardiogram (ultrasound of the heart).

A cardioembolic stroke occurs when the heart pumps unwanted materials into the brain. When this type of stroke is suspected in patients, which is often the case in cryptogenic stroke, we do further testing including Transcranial Doppler — a measure of the velocity of blood flow through the brain vessels — and long-term heart rhythm monitoring. Our cardiologists can also implant a device which can monitor heart rhythm for more than a year.

The earlier we can determine etiology, the earlier we can treat and prevent future strokes.

When a stroke occurs, you need prompt, experienced care. Rest assured that if you or a loved one have a stroke, you can find that care at the Southeast Regional Stroke Center at Erlanger, the region’s only comprehensive stroke center.