How Healthcare Providers Find the Cause of a Cryptogenic Stroke

A cryptogenic stroke is a stroke of unknown cause. This means that the stroke cannot be attributed to any specific cause or risk factor, even after thorough testing. Before labeling any stroke a cryptogenic stroke, your stroke team will search for the common and uncommon causes of stroke. The most common causes of stroke include smoking, heart disease, high blood pressure, vascular disease, and high cholesterol.

Patient lying inside a medical scanner
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What Is a Stroke?

A stroke is brain damage due to the interruption of blood flow to a region of the brain. It is among the top causes of death and disability in the United States. A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a blood clot or bleeds. When that happens, part of the brain cannot get the blood, oxygen, and nutrients it needs, so the brain cells in that region may suffer permanent damage.


The brain is an extremely complex organ that controls thinking, movement, and sensation. If a stroke occurs and blood flow can't reach the region that controls a particular body function, that part of the body won't work as it should.

Because the different areas of the brain all control specific functions, a stroke can cause any physical or cognitive (thinking) problems.

Most of the time, your medical team can effectively diagnose a stroke. The next step is urgent stabilization of your medical condition and stroke treatment to minimize any damage from the stroke.

Why It's Important to Figure out the Cause

A stroke can be caused either by a blood clot blocking the flow of blood to the brain (called an ischemic stroke) or by bleeding of a blood vessel (called a hemorrhagic stroke). A TIA (transient ischemic attack), or "mini-stroke", is caused by a temporary blood clot that resolves and does not cause permanent damage.

If you have a TIA or an ischemic stroke, the potential causes are somewhat different than the causes of a hemorrhagic stroke. The reason that your medical team works so hard to search for and identify the cause of your stroke is that your stroke risk can often be controlled and managed, substantially reducing your chances of having another stroke.

A stroke typically occurs as the result of years of buildup of disease in the blood vessels of the heart or the brain. Most people who experience a stroke are at high risk of having another stroke. Having one stroke causes a handicap, and having another stroke adds another handicap, which can significantly interfere with your daily life.

How Your Medical Team Searches for the Cause

If you have had a stroke, you can expect a number of medical tests that examine the structure of your brain to see exactly where the stroke is located and what type of stroke it is. These tests include brain imaging tests, such as Brain MRI, Brain CT, Brain MRA, and Brain MRV. It is unlikely that you would need to have all of these imaging tests, because one test may give enough answers so that other tests are not needed.

When it comes to searching for the underlying cause of your stroke, your healthcare provider may order any of a number of blood tests that examine your heart, your blood clotting tendency, your vitamin B12 level, and even your thyroid function. Again, you would not need to have all of these tests. Your healthcare provider will decide which tests to order depending on your medical history, your family history, the type of stroke you had and the results of preliminary tests.

There are also some lifestyle factors that can add to your risk of strokes, such as smoking, a high-fat diet, major stress and mood problems and lack of physical exercise. Less common causes of stroke include pregnancy or the use of birth control pills. Post-menopausal hormone therapy may pose special stroke risks for women and the use of testosterone therapy for men may increase the risk of stroke.

A Word From Verywell

If you have been told that you have had a cryptogenic stroke, you might be concerned about your health. However, rest assured that the process of searching for causes after a cryptogenic stroke generally uncovers previously unnoticed health problems — ultimately resulting in better health when those problems are addressed and managed.

As you recover from your stroke, you may need one or more types of rehabilitation programs. You should also learn as much as you can about stroke prevention so that you can make the lifestyle changes necessary to prevent yourself from experiencing another stroke.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Jose Vega MD, PhD
Jose Vega MD, PhD, is a board-certified neurologist and published researcher specializing in stroke.