When doctors cannot determine the cause of an individual’s stroke, the stroke is cryptogenic. Most cryptogenic strokes may have an ischemic origin. This means they develop due to a blockage in a blood vessel that reduces the blood flow to the brain.

There is some uncertainty over what it means for strokes to be cryptogenic. As a 2016 study notes, scientists define cryptogenic strokes as those with causes doctors cannot explain. However, there is no universally accepted definition of what this means.

A 2022 overview of research states that from the age of 25 years, an individual has an approximately 25% risk of having a stroke. The majority of these are ischemic strokes, which occur when something blocks or narrows a blood vessel in the brain.

Of these strokes, roughly 35% are cryptogenic, although scientists are unsure about their true prevalence.

This article provides a detailed overview of cryptogenic strokes, including their symptoms, causes, and risk factors. It will go on to discuss the diagnosis, treatment, and outlook for cryptogenic stroke before detailing some preventive measures.

A doctor performing tests to diagnose a cryptogenic stroke -2.Share on Pinterest
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The only difference between typical and cryptogenic strokes is whether doctors can determine the cause. For this reason, the symptoms of a cryptogenic stroke are the same as those of any other stroke.

According to the Centers for Disease Control and Prevention (CDC), these symptoms include sudden:

  • weakness in the face, leg, or arm, especially if this weakness affects only one side of the body
  • vision difficulties, which could affect one or both eyes
  • walking problems
  • dizziness, lack of coordination, or lack of balance
  • confusion, problems with speaking, or problems with understanding
  • severe headache, seemingly without a cause

A stroke is a medical emergency, and anyone with signs of stroke needs immediate medical attention.

Learn more about the symptoms of a stroke.

A cryptogenic stroke refers to a stroke of unknown cause. However, doctors and scientists can make educated guesses about what causes them.

According to the American Stroke Association, some possible causes of cryptogenic stroke include:

  • patent foramen ovale — a hole that develops between the left and right upper chambers of the heart
  • atrial fibrillation — an atypical heart rhythm
  • a fatty buildup of plaque inside the aorta
  • a disposition to form blood clots

In some cases, a cryptogenic stroke could arise from infection, cancer, or a tear in an artery wall. However, these causes of stroke are less common than those above.

Stroke risk factors can increase the risk of someone developing a stroke. However, they are not necessarily causes of stroke and do not mean that the individual will experience one.

A 2023 overview lists the following as risk factors for stroke:

  • being older
  • being male
  • a family history of stroke or similar diseases
  • certain genetic conditions, such as sickle cell disease

It is unclear whether these risk factors are different for cryptogenic stroke specifically.

Some studies suggest, in comparison with the general United States population, Hispanic people are 46% more likely to have a cryptogenic stroke, while African Americans are twice as likely. However, more research is necessary to verify these findings.

Authors of a 2016 article state that cryptogenic strokes remain a diagnostic challenge.

They also suggest that all cryptogenic strokes may be ischemic in origin. Therefore, some healthcare professionals believe that to diagnose a cryptogenic stroke, they must not be able to detect other causes of a stroke despite using the best diagnostic tools for ischemic strokes.

These methods include:

  • CT and MRI scans
  • electrocardiography
  • echocardiography
  • cardiac rhythm monitoring
  • blood biomarker tests

However, not everyone accepts this definition. For this reason, the diagnosis of cryptogenic stroke remains an issue for scientific debate.

Since doctors cannot be certain that someone’s cryptogenic stroke is ischemic, treating these strokes can be complicated.

However, there is evidence that anticoagulants are a useful form of treatment for cryptogenic stroke. In particular, these medications seem to help with preventing a second stroke.

According to the above 2016 study, scientists disagree about the outlook for cryptogenic stroke. This is because different studies use different definitions of this stroke type, which makes comparing them difficult.

However, evidence suggests that people have a 29% chance of having another stroke within 31 months of a cryptogenic stroke. For comparison, that figure is 27% for cardioembolic strokes and 13% for artery atherosclerosis and lacunar strokes.

Some people who experience a cryptogenic stroke will never have another stroke. However, strokes can lead to brain damage, which can cause long-term neurological impairments. Even with treatments, these impairments can greatly affect an individual’s quality of life.

It is impossible for an individual to prevent a stroke with complete certainty. However, some stroke risk factors are modifiable, which means that people could prevent a stroke by avoiding these.

The above 2023 overview lists the following as modifiable stroke risk factors:

  • eating a non-nutritious diet
  • smoking
  • drinking alcohol
  • not regularly exercising
  • having obesity
  • having high blood pressure
  • having diabetes
  • having atrial fibrillation

An individual who has concerns about lowering their risk of stroke can speak with a doctor for guidance and support.

A stroke occurs when there is reduced blood flow within a person’s brain. They can arise from brain blood vessel ruptures — these are hemorrhagic strokes. Other strokes arise when a brain blood vessel has a blockage or becomes too narrow.

Sometimes, doctors are unable to determine the cause of a stroke — these are cryptogenic strokes. Their symptoms and risk factors are the same as those of regular strokes.

There is some evidence that all cryptogenic strokes have an ischemic origin. This would explain why anticoagulants are effective in treating both types of stroke. Treatment for cryptogenic strokes nonetheless remains challenging.