Vertebrobasilar stroke is a type of stroke that occurs when blood flow to the back part of the brain is interrupted. While less common than other stroke types, it carries a particularly high risk of death and long-term disability due to symptoms that can easily be mistaken for less serious conditions.

A vertebrobasilar stroke happens when the blood vessels supplying the posterior, or back portion, of the brain become blocked or severely restricted. This area of the brain controls many essential functions, including balance, vision, coordination, consciousness, and basic life-sustaining processes like breathing and heart rate. When these areas don’t receive enough oxygen-rich blood, brain cells begin to die within minutes, leading to a stroke.

The name comes from the specific blood vessels involved in this type of stroke. The vertebral arteries, which are two major blood vessels that run up each side of the neck through the spine, join together at the base of the skull to form the basilar artery. Together, these vessels make up what doctors call the vertebrobasilar system or posterior circulation. This network supplies blood to critical brain structures including the brainstem (which contains the midbrain, pons, and medulla), the cerebellum (which controls coordination and balance), the thalamus (which processes sensory information), and parts of the occipital and temporal lobes responsible for vision and memory.

What makes vertebrobasilar strokes particularly dangerous is that their symptoms often don’t look like what most people expect from a stroke. Instead of the classic signs like facial drooping or arm weakness on one side, people experiencing this type of stroke might primarily feel dizzy, nauseated, or have vertigo. These symptoms can easily be mistaken for an inner ear problem, food poisoning, or even a migraine. This confusion can lead to dangerous delays in getting emergency medical treatment, which is why vertebrobasilar strokes have such a high mortality rate.

How Common Is Vertebrobasilar Stroke?

Vertebrobasilar strokes account for approximately 20% of all strokes and transient ischemic attacks. This means that roughly one out of every five strokes affects the posterior circulation system rather than the front part of the brain. While this makes them relatively less common than strokes affecting the anterior circulation, they represent a significant portion of all cerebrovascular events.

The condition is more likely to affect certain groups of people. Men face approximately twice the risk of vertebrobasilar insufficiency compared to women. The risk also increases significantly with age, with as many as 25% of people over age 70 showing some degree of reduced blood flow to the posterior brain regions. People over age 50 are at particularly elevated risk, especially if they have other health conditions.

Despite representing only about 20% of all strokes, vertebrobasilar strokes carry a mortality rate of more than 85% when large vessels are completely blocked. This exceptionally high death rate reflects both the critical nature of the brain structures affected and the challenges in recognizing and treating these strokes quickly. The areas supplied by the vertebrobasilar system control so many vital functions that damage to them often results in severe, life-threatening complications.

Geographic location also plays a role in stroke risk. In the United States, people living in what is known as the “stroke belt,” primarily in the Southeast, experience higher rates of all types of strokes, including vertebrobasilar strokes. Additionally, Black Americans face a higher risk of vertebrobasilar disease compared to other ethnic groups, though the reasons for this disparity involve a complex interaction of genetic, environmental, and socioeconomic factors.

What Causes Vertebrobasilar Stroke?

Strokes occur when something blocks the blood supply to part of the brain, or when a blood vessel in the brain bursts. The brain requires a constant supply of oxygen to function, and this oxygen arrives via blood pumped through arteries. When blood flow stops or becomes severely restricted, brain cells begin dying within minutes because they cannot survive without oxygen. This process of cell death is what causes a stroke and its resulting symptoms.

The most common underlying cause of vertebrobasilar stroke is atherosclerosis, which is the hardening and narrowing of arteries. This condition develops gradually over time as deposits of cholesterol, calcium, and other cellular materials build up on the inner walls of arteries, forming structures called plaques. These plaques not only make the arteries harder and less flexible, they also grow larger over time, progressively narrowing the space through which blood can flow. Eventually, a plaque can become large enough to significantly restrict blood flow, or a piece of plaque can break off and travel downstream to block a smaller vessel completely.

Strokes can be divided into two main categories: ischemic and hemorrhagic. Ischemic strokes occur when blood flow is blocked, while hemorrhagic strokes occur when a blood vessel ruptures and bleeds. Ischemic strokes are further categorized based on what caused the blockage. Lacunar strokes are caused by uncontrolled high blood pressure damaging small vessels, most commonly in the internal capsule or thalamus, though they can occasionally affect the brainstem. Thrombotic strokes happen when excessive atherosclerosis causes a clot to form right at the site of a narrowed artery. Embolic strokes occur when a blood clot or piece of plaque forms somewhere else in the body, travels through the bloodstream, and eventually lodges in and blocks a brain artery.

Hemorrhagic strokes in the vertebrobasilar territory are often the result of ruptured aneurysms, uncontrolled high blood pressure, blood vessel abnormalities, cancer that has spread to the brain, or diseases affecting brain vessels. Less common causes of vertebrobasilar stroke include vertebral artery dissection (a tear in the artery wall), penetrating artery disease (when small arteries in the brain become blocked), pulmonary embolism, blood disorders that affect clotting, drug addiction, fibromuscular dysplasia (an abnormal cell development in artery walls), and even severe migraine headaches.

Who Is at Risk?

The risk factors for vertebrobasilar stroke are the same as those for other types of strokes, as they all relate to the health of blood vessels throughout the body. High blood pressure, or hypertension, is the most common risk factor, present in about 70% of stroke patients. When blood pressure remains elevated over time, it damages the walls of arteries, making them more susceptible to atherosclerosis and increasing the likelihood of both ischemic and hemorrhagic strokes.

Diabetes mellitus is another major risk factor because high blood sugar levels over time damage blood vessels throughout the body, including those in the brain. Cigarette smoking accelerates the development of atherosclerosis, increases blood pressure, and makes blood more likely to clot. Obesity contributes to stroke risk both directly and indirectly by increasing the likelihood of developing other risk factors like high blood pressure, diabetes, and high cholesterol.

Atrial fibrillation, an irregular heart rhythm, significantly increases stroke risk because the abnormal heart rhythm can allow blood clots to form in the heart chambers. These clots can then travel to the brain and cause an embolic stroke. A sedentary lifestyle without regular physical activity contributes to obesity, high blood pressure, and diabetes. Hyperlipidemia, which means elevated levels of fats in the blood, particularly high cholesterol, accelerates the formation of atherosclerotic plaques in arteries.

Illicit drug use, particularly cocaine, can cause strokes through multiple mechanisms including sudden spikes in blood pressure, blood vessel inflammation, and increased blood clotting. Hypercoagulable states, which are conditions that make blood clot too easily, can lead to stroke by causing clots to form in brain arteries. Other heart conditions that increase risk include blood clotting disorders, infective endocarditis (infection of heart valves), and vertebral artery dissection.

People with coronary artery disease or peripheral artery disease face elevated risk because these conditions indicate that atherosclerosis is already affecting their blood vessels. A family history of vertebrobasilar insufficiency or stroke also increases risk, suggesting genetic factors play a role. Age over 50, particularly over 70, is a significant risk factor as atherosclerosis typically develops over many years.

Recognizing the Symptoms

The symptoms of vertebrobasilar stroke can vary widely depending on which parts of the posterior brain are affected and how severely blood flow is restricted. This variability makes diagnosis challenging, as symptoms may resemble many other medical conditions. Understanding these symptoms is crucial because recognizing them quickly and seeking immediate medical attention can be life-saving.

Vertigo, which is a spinning sensation where you feel like you or the room around you is moving, is one of the most commonly reported symptoms. Unlike simple dizziness, vertigo from a vertebrobasilar stroke is usually sudden, severe, and accompanied by other neurological symptoms. Nausea and vomiting frequently accompany the vertigo, which is why many people mistakenly think they have a stomach virus or food poisoning rather than a stroke.

Vision problems are very common with vertebrobasilar strokes because the posterior circulation supplies the occipital lobes, which process visual information. Symptoms can include blurred vision, double vision (seeing two of everything), temporary loss of vision in one or both eyes, graying or clouding of vision, or loss of portions of the visual field. Some people describe their vision as if they’re looking through a fog or as if a curtain has been drawn across part of their sight.

Balance problems and difficulty walking occur because the cerebellum, which coordinates movement and maintains balance, is supplied by the vertebrobasilar system. People may find themselves suddenly unsteady on their feet, veering to one side when trying to walk, or experiencing what doctors call “drop attacks” where they suddenly fall to the ground without losing consciousness. Loss of coordination and ataxia (uncoordinated movements) make even simple tasks like reaching for objects or walking in a straight line difficult or impossible.

Speech difficulties, called dysarthria, occur when stroke affects the parts of the brainstem that control the muscles used for speaking. Speech may become slurred, garbled, or difficult to produce. Unlike some other types of strokes where people lose the ability to understand or form words, in vertebrobasilar stroke the problem is usually with the physical production of speech. Difficulty swallowing, or dysphagia, also results from brainstem involvement and can be dangerous as it increases the risk of choking or inhaling food or liquids into the lungs.

Numbness or tingling can affect any part of the body, but the pattern may be unusual compared to other stroke types. Because of how sensory pathways are organized in the brainstem, vertebrobasilar strokes can cause what doctors call “dissociated sensory loss,” where one type of sensation (like pain and temperature) is lost while another type (like touch and position sense) is preserved. Some people experience numbness on one side of the face and the opposite side of the body, a pattern called “crossed paresis” that is characteristic of brainstem lesions.

Headaches, particularly in the back of the head, may occur with vertebrobasilar strokes. Abnormal eye movements, including involuntary jerking movements called nystagmus, lateral gaze abnormalities where the eyes cannot move fully in certain directions, and changes in pupil size can all indicate brainstem involvement. Changes in consciousness level, ranging from confusion to complete loss of consciousness, reflect damage to the parts of the brainstem that regulate alertness and awareness.

Other symptoms may include weakness in the limbs, particularly affecting both legs or all four limbs rather than just one side of the body, which is more typical of strokes affecting the front of the brain. Horner syndrome, with drooping eyelid, smaller pupil, and decreased sweating on one side of the face, can occur with vertebrobasilar strokes. Urinary incontinence and sudden generalized weakness are also possible symptoms.

Prevention Strategies

Preventing vertebrobasilar stroke involves addressing the underlying risk factors that contribute to blood vessel disease. While some risk factors like age and family history cannot be changed, many can be modified through lifestyle changes and medical treatment. The goal of prevention is to keep blood vessels healthy and maintain good blood flow to the brain throughout life.

Stopping smoking is one of the most important steps anyone can take to reduce stroke risk. Smoking damages blood vessel walls, accelerates atherosclerosis, increases blood pressure, and makes blood more likely to clot. The benefits of quitting begin almost immediately, with stroke risk dropping significantly within just a few years of stopping. Even people who have smoked for decades can reduce their risk by quitting.

Regular physical activity helps prevent stroke through multiple mechanisms. Exercise helps control weight, lowers blood pressure, improves cholesterol levels, helps manage blood sugar, and keeps blood vessels flexible and healthy. Most experts recommend at least 150 minutes of moderate-intensity aerobic activity per week, such as brisk walking, swimming, or cycling. Even people who have been inactive for years can benefit from starting an exercise program, though it’s wise to consult a doctor before beginning if you have existing health conditions.

Following a heart-healthy diet low in saturated fats, trans fats, and cholesterol helps prevent the buildup of plaques in arteries. A diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats from sources like fish, nuts, and olive oil provides the nutrients blood vessels need to stay healthy while limiting the substances that contribute to atherosclerosis. Reducing salt intake helps control blood pressure, while limiting alcohol consumption prevents blood pressure spikes and other health problems.

Careful management of diabetes is essential for preventing blood vessel damage that leads to strokes. This means monitoring blood sugar levels regularly, taking prescribed medications as directed, following dietary recommendations, exercising regularly, and maintaining regular contact with healthcare providers to adjust treatment as needed. Keeping blood sugar levels as close to normal as possible protects blood vessels throughout the body, including those supplying the brain.

Regular health screenings allow early detection and treatment of risk factors before they cause serious problems. Blood pressure should be checked regularly, as hypertension often causes no symptoms until it has already damaged blood vessels. Cholesterol levels should be monitored through blood tests, and medication may be prescribed if levels are too high despite lifestyle changes. People with atrial fibrillation may need blood-thinning medications to prevent clot formation.

Maintaining a healthy weight reduces the burden on the cardiovascular system and helps prevent or control diabetes, high blood pressure, and high cholesterol. Even modest weight loss can significantly improve these risk factors. Managing stress through techniques like meditation, yoga, adequate sleep, and healthy coping strategies may also contribute to stroke prevention by helping control blood pressure and reducing inflammation in the body.

How the Disease Changes the Body

Understanding the pathophysiology, or how vertebrobasilar stroke changes normal body functions, helps explain why symptoms occur and why this condition is so serious. The brain is an extremely active organ that requires a constant supply of oxygen and glucose to function. Unlike other organs that can store energy or function briefly without oxygen, brain cells begin to die within minutes when blood supply is cut off.

When atherosclerosis develops in the vertebral or basilar arteries, plaques made of cholesterol, calcium, and other materials accumulate on the inner walls of these vessels. These plaques gradually narrow the space through which blood can flow, a process that typically develops over many years. As the narrowing progresses, blood flow to the posterior brain becomes restricted, a condition called vertebrobasilar insufficiency. Initially, this reduced flow may cause only occasional symptoms, particularly during activities that increase the brain’s oxygen demand or temporarily reduce blood pressure.

When a complete blockage occurs, either because a plaque grows large enough to occlude the vessel or because a blood clot forms at the site of a plaque, the sudden loss of blood flow creates an ischemic stroke. The area of brain tissue downstream from the blockage immediately enters a critical state. The core of this area, which has the most severely reduced blood flow, begins dying almost instantly. Surrounding this core is an area called the penumbra, where blood flow is reduced but not completely absent. Cells in the penumbra are injured but not yet dead and may be salvageable if blood flow can be restored quickly.

The brainstem structures supplied by the vertebrobasilar system control many automatic functions that we don’t consciously think about. The medulla regulates breathing, heart rate, and blood pressure. The pons plays a role in sleep, bladder control, hearing, taste, and eye movement. The midbrain is involved in vision, hearing, motor control, and alertness. When stroke damages these areas, the effects can be devastating and immediately life-threatening.

The cerebellum, which coordinates movement and maintains balance, requires a constant blood supply to function properly. When vertebrobasilar stroke affects the cerebellum, people lose the ability to coordinate their movements smoothly. Simple actions like reaching for a cup or walking across a room become difficult or impossible. The thalamus, which acts as a relay station for sensory information traveling to the conscious parts of the brain, may also be affected, causing unusual patterns of numbness or altered sensation.

Because many cranial nerves, which control facial movement, eye movement, swallowing, and other functions, either originate in the brainstem or pass through it, vertebrobasilar strokes frequently affect these nerves. This can result in facial weakness or paralysis, difficulty moving the eyes in certain directions, problems with hearing or balance from inner ear nerve involvement, and difficulty swallowing. The pattern of deficits depends precisely on which level of the brainstem is affected.

One characteristic feature that helps doctors identify brainstem strokes is “crossed paresis,” where paralysis or weakness affects the face on the same side as the stroke but affects the arm and leg on the opposite side. This occurs because nerve pathways cross over at different levels, so damage at the brainstem level affects different body parts on different sides. This crossing pattern is quite different from strokes affecting the front of the brain, where symptoms typically affect one entire side of the body.

When large vessels in the vertebrobasilar system become completely blocked, the mortality rate exceeds 85%, and most survivors face severe, permanent disabilities. These may include quadriplegia (paralysis of all four limbs), hemiplegia (paralysis of one side of the body), difficulty swallowing that makes eating dangerous, inability to speak clearly, vision problems, chronic dizziness, and dysfunction affecting multiple body systems. Many survivors require long-term care and extensive rehabilitation.

However, not all vertebrobasilar strokes are massive. Many arise from disease in small vessels and affect only discrete areas of the brainstem. These smaller strokes, while still serious, often have a more benign prognosis with reasonable functional recovery possible. The location of the stroke matters as much as its size in determining outcomes.