Understanding Stroke

A stroke is a brain, spinal cord, or retinal injury related to dysfunction of the blood vessels supplying these parts of the central nervous system, resulting in permanent damage. When cells (neurons) or nerve fibers (axons) are injured, specific functions of the nervous system are impaired or lost: the ability to speak or comprehend others, the ability to move the face or limbs, the ability to see throughout one’s vision, and more.

A stroke is typically classified in one of two ways:

1. Ischemic stroke (the majority of strokes): a blockage of a blood vessel supplying a specific portion of the brain, resulting in loss of oxygen and nutrient delivery to that area.
2. Intracerebral hemorrhage: a rupture of a blood vessel supplying the brain, resulting in bleeding into the brain tissue.

Ischemic strokes typically have a single cause, but the cause can differ greatly from one person to the next.

For older adults, the causes of stroke may be related to common “risk factors” for stroke and heart disease. Stroke is a brain disease, not a heart disease, but both the brain and the heart can be injured by the same medical problems.

1. Atrial fibrillation – An abnormal heart rhythm resulting in clot formation in the left atrium of the heart. This becomes more common as we age.
2. Large artery atherosclerosis – Cholesterol plaque buildup in the arteries of the head and neck. Conditions such as hypertension (high blood pressure), hypercholesterolemia (elevated blood cholesterol), diabetes (high blood sugar), and tobacco use damage these large arteries and increase plaque buildup over time.
3. Small vessel occlusion – Weakening of the small arteries in the head, leading to collapse of the blood vessels. Risk factors such as hypertension (high blood pressure), hypercholesterolemia (elevated blood cholesterol), diabetes (high blood sugar), and tobacco use also damage these small arteries.

For younger adults, the causes of stroke are often less connected to prior medical problems. Some of these include:

1. Patent foramen ovale – A small tunnel between two chambers of the heart, leading to passage of a clot through the heart or a formation of a clot in the tunnel itself.
2. Arterial dissection – A tear in the wall of a blood vessel in the head or neck, leading to obstruction of blood flow.
3. Reversible cerebral vasoconstriction syndrome – Abnormal, excess squeezing of the walls of blood vessels in the head.
4. Cerebral venous sinus thrombosis – Clot formation in the blood vessels draining blood away from the head.
5. Hypercoagulability – A change in the body’s balance between clotting and bleeding, leading to excess clot formation.
6. Vasculitis – A condition triggering an immune system attack on the blood vessels, leading to swelling of the blood vessel walls.

Intracerebral hemorrhages may have multiple contributing causes. These include:

1. Hypertension – High blood pressure can break the walls of small arteries, causing bleeding in the brain.
2. Cerebral amyloid angiopathy – With age, abnormal proteins including amyloid may deposit in the walls of arteries. These weaken the infrastructure of the arteries and make them more susceptible to injury and rupture.
3. Medication-related – Some medications such as anticoagulants (e.g. Coumadin/warfarin) or antiplatelet medications (e.g. aspirin, Plavix/clopidogrel) that are used to prevent ischemic stroke and treat heart conditions can exacerbate bleeding in the brain.
4. Vascular malformations – Blood vessels can sometimes develop abnormally early in life (e.g. arteriovenous malformations, cavernous malformations) or change when exposed to conditions that damage blood vessels such as hypertension and tobacco use (e.g. aneurysms). These are often more fragile than normal blood vessels and can rupture more easily.
5. Other medical conditions – Some illnesses increase risk of bleeding such as liver disease, hemophilia, and kidney disease.
6. Trauma – Physical injury from a fall or head strike can sometimes cause bleeding into the brain tissue (although this usually results in bleeding outside the brain tissue or on the scalp). 

For stroke, sometimes the specific cause (or mechanism) is not clearly determined after a comprehensive evaluation (including a careful history, examination, and tests). In these cases, the stroke is deemed cryptogenic and the stroke specialist will help guide you in determining the best course of action, even if there is not a single, clear “right” answer.

Stroke is the leading cause of disability and the third leading cause of death in the United States. Stroke can affect people of any age, including babies, children, young adults, middle-aged adults, and elderly adults.

According to the Centers for Disease Control and Prevention, stroke affects more than 795,000 adults in the U.S. each year. However, many strokes remain undiagnosed when individuals do not receive medical attention for their symptoms, or if their symptoms are not recognized as stroke symptoms.

At any given time, there are about 6.5 million stroke survivors in the U.S. While some are severely disabled by their strokes, many recover and are able to return to prior roles and responsibilities. Among those with impaired walking due to stroke, the vast majority will be able to walk again with rehabilitation and time for recovery.

Common symptoms of a stroke relate to loss of function for the brain, spinal cord, or the retina of the eye. These include:

• Weakness of one side of the face (difficulty closing the eyes or moving the mouth)
• Weakness of one side of the body (difficulty moving the arm or leg on one side)
• Loss of sensation on one side of the face or body (numbness or tingling on one side)
• Trouble with speaking (expressing thoughts in words)
• Trouble with understanding others (comprehending spoken or written language)
• Trouble with seeing (partial loss of vision in one or both eyes or double vision)
• Trouble with coordination (moving the arms or legs appropriately)
• Trouble with balance (resulting in falling to one side)

Most symptoms of stroke develop suddenly, but they can sometimes be gradual or fluctuating (come-and-go). The symptoms may be mild or severe.

If you or a loved one ever experiences any of these symptoms, call 911 immediately. An emergency medical team in an ambulance can call ahead to the Stroke Center, allowing faster mobilization of the Stroke Team and quicker treatment. Every minute an artery is blocked, 2 million brain cells die. Rapid treatment of a stroke can improve outcomes and save lives.

The diagnosis of stroke is usually directed by a neurologist with the help of a team of resident physicians, Emergency Medicine physicians, nurses, emergency medical technicians, and others. The most important information for securing the diagnosis are your symptoms and your neurologic examination. Many physicians and nurses will ask you questions about your symptoms, usually repeatedly over the course of several evaluations, to confirm and glean additional details from your memory of your experience. Physicians and nurses will also repeatedly examine you to monitor your symptoms and deficits: this helps guide treatment decisions as they work to stabilize your condition.

In most cases, several tests will occur during and after the hospitalization. You may not undergo all of these tests, but your doctors will specifically tailor these tests to you. These include the following:

• Head CT scan – A rapid, three-dimensional X-ray of the brain to quickly assess for bleeding in the head. This does not usually confirm the presence of an ischemic stroke, but it can help determine the safety of emergency treatments such as IV tPA and mechanical thrombectomy.
• CT angiogram of the head and neck – A rapid scan of the blood vessels of the head and neck with an iodine-containing contrast dye injected into the bloodstream that can confirm the presence of large artery blockages and vascular malformations.
• Electrocardiogram (ECG or EKG) – An electrical test that records your heart beat to assess the rate and rhythm.
• Blood tests – Tests to assess for cholesterol levels, blood sugar levels, and other risk factors for stroke. These tests also check blood electrolytes and blood cell counts to monitor for issues that may worsen the stroke (i.e. infection, high blood sugar, etc.).
• Chest x-ray – An x-ray to assess for infection or aspiration (i.e. accidentally swallowing food particles into the lungs as a result of difficulty swallowing).
• Urine tests – Tests to assess for infection and other conditions that worsen the stroke.
• Cardiac telemetry – An electrical test with stickers on the chest to monitor the heart rhythm for abnormalities (including atrial fibrillation).
• Brain MRI – A slower brain scan providing high resolution pictures that can confirm the diagnosis of stroke and provide additional information on the cause of the stroke.
• Echocardiogram – An ultrasound of the heart that provides information on heart muscle and valve function. This can be performed as a transthoracic echocardiogram on the surface of the chest or as a transesophageal echocardiogram where you swallow a small camera to look more closely at the heart. The type of study selected will be related to concerns about causes of stroke specific to you.
• Catheter angiogram – A minimally-invasive surgical test involving a wire catheter injecting an iodine-containing dye into the arteries of the head and neck to obtain high-resolution pictures of the blood vessels.
• CT of the torso – A three-dimensional x-ray study that looks for conditions that may increase blood clotting, including unrecognized cancers.
• MRI of the pelvis – A slower scan of the veins of the pelvis looking for deep vein clots.
• Doppler ultrasound of the legs – An ultrasound of the deep veins of the legs looking for deep vein clots.

Risk factors are conditions that contribute to specific causes (or mechanisms) of stroke. Some of these contribute to both ischemic stroke and intracerebral hemorrhage. Risk factors are important to identify and address in order to reduce the chances of having another stroke in the future. Stroke can be prevented!

For ischemic stroke in older adults, the most common risk factors are:

• Hypertension (high blood pressure)
• Atrial fibrillation (an abnormal heart rhythm)
• Hypercholesterolemia (elevated blood pressure)
• Diabetes (high blood sugar)
• Tobacco use
• Obesity
• Obstructive sleep apnea
• Lack of exercise
• Poor diet
• Excess alcohol consumption

For ischemic stroke in younger adults, the most common risk factors are:

• Patent foramen ovale (a small tunnel between two chambers in the heart)
• Injury to the neck or neck manipulation
• Pregnancy
• Migraine
• Tobacco use
• Excess alcohol consumption
• Drug use (including marijuana, cocaine, heroin, amphetamines, etc.)

For intracerebral hemorrhage, the most common risk factors are:

• Hypertension (high blood pressure)
• Cerebral amyloid angiopathy
• Blood-thinning medications (i.e. anticoagulants)
• Vascular malformations (i.e. aneurysms, arteriovenous malformations, cavernous malformations)