What is a stroke?
Stroke is an injury to the brain that occurs when the brain's blood supply is interrupted. Blood carries oxygen which is necessary for all cells in the body to survive. The brain has one of the highest demands for oxygen. In fact, cells in the brain start to die if they are without oxygen-rich blood for more than a few minutes. The death of these brain cells can result in permanent brain damage. Other terms for stroke include cerebrovascular accident (CVA) or brain attack.
Blood vessels that carry blood from the heart to the body are called arteries. Oxygen-rich blood is delivered to the brain through the carotid arteries along both sides of the neck. These arteries split into several smaller vessels that reach throughout the brain and skull. Damage or blockage to any of these arteries can slow or stop blood flow to the brain. The severity of brain damage will depend on the amount of brain tissue affected, the length of time the blood flow is impaired, and the area of the brain affected.
Types and Causes of Stroke
An ischemic stroke occurs when a blood vessel of the brain becomes blocked. Nearly 90 percent of all strokes are ischemic. Blockage may be caused by:
- Carotid artery stenosis. Narrowing of the carotid arteries that supply blood to the brain. The narrowing occurs as a result of atherosclerosis, the build up of plaque (fat, cholesterol, and other substances) inside artery walls.
- Thrombus. A blood clot that forms in the arteries of the brain, often a result of atherosclerosis.
- Embolism. A blood clot that travels from another part of the body. In many cases, the clot travels from the heart and gets trapped in the arteries that supply blood to the brain. A common cause of embolism is atrial fibrillation, a type of heart arrhythmia.
- Arterial spasm. Blood vessels have muscular walls that can tighten or loosen to help blood flow. Problems with nerves, blood vessel structure, injuries, or stimulants can cause these muscles to spasm and tighten, making it difficult for blood to flow through the blood vessel. Although spasms can cause problems on their own, they may be more likely to cause blockages in blood vessels with current atherosclerosis.
A stroke may also occur if a blood vessel breaks and bleeds into or around the brain. Hemorrhagic stroke is the most common type of stroke in young people. The leading causes of this type of stroke are:
- Hypertension. Blood pressure is the force of blood on arteries walls. Prolonged high blood pressure damages and weakens blood vessels.
- Brain aneurysm. An aneurysm is an outpouching of a blood vessel wall in the brain that form in areas where the artery wall is weak or thin. The bulging, blood-filled pocket can put pressure on parts of the brain. Aneurysms that burst often have devastating consequences.
- Ateriovenous malformations (AVM). A rare condition marked by abnormal connections that occur between arteries and veins. Instead of an artery supplying an area of the brain with blood, it is connected directly to a vein that takes it away, bypassing the brain tissue that needs it. The blood vessels may be weakened over time. This, in turn, may cause widening of the vessels, which may eventually burst.
A silent stroke occurs without any typical signs or symptoms of a stroke. Despite this, silent strokes cause damage to brain tissue and increase the risk of a major stroke in the future. Silent strokes tend to occur in silent areas of the brain that are not obviously active in cognitive function or mobility. Brain tissue damage is usually found incidentally during imaging tests.
Certain factors increase your risk of stroke but can not be changed, such as:
- Race: People of African American, Hispanic, or Asian/Pacific Islander descent are at increased risk
- Age: Older than 55 years of age
- Family history of stroke
Other factors that may increase your risk can be changed such as:
- Drug abuse from cocaine, amphetamines, or heroin use
- Physical inactivity
Certain medical condition that can increase your risk of stroke. Management or prevention of these conditions can significantly decrease your risk. Medical conditions include:
- High blood pressure
- High cholesterol levels – specifically high-LDL bad cholesterol
- Low bone mineral density, especially in women
- Obesity and metabolic syndrome
- High blood homocysteine level
- Diabetes mellitus or impaired glucose tolerance
- Atrial fibrillation
- Blood disorders such as sickle cell disease and polycythemia
- Vascular dementia
- Disease of heart valves, such as mitral stenosis
- Prior stroke or cardiovascular disease, such as heart attack
- Peripheral artery disease
- Transient ischemic attack (TIA) – a warning stroke with stroke-like symptoms that go away shortly after they appear
- Conditions that increase your risk of blood clots such as:
- Certain autoimmune diseases
- Migraine with aura
- Having a blood vessel abnormality
Risk factors specific to women include:
- Previous pre-eclampsia
- Use of birth control pills, especially if you are over 35 years old and smoke
- Long-term use of hormone replacement therapy
- Pregnancy – due to increased risk of blood clots
Symptoms & Diagnosis
Symptoms of a cerebellar stroke come on suddenly and may include:
- Uncoordinated movements of the limbs or trunk (ataxia)
- Difficulty walking, including problems with balance
- Abnormal reflexes
- Vertigo – a feeling of spinning or whirling when you are not moving
- Nausea and vomiting
- Intense headache
- Speech problems and difficulty swallowing
- Problems sensing pain and temperature
- Difficulty hearing
- Problems with vision (e.g., eyes move rapidly, difficulty controlling eye movement)
- Problems with eyes (e.g., small pupil, droopy eyelid)
- Loss of consciousness
If you or someone you know has any of these symptoms, call for emergency medical services right away. Brain tissue without blood flow dies quickly. Early care can decrease damage.
A physical exam will be done to look for muscle weakness, visual and speech problems, and movement difficulty. If possible, you will be asked about your symptoms and medical history.
Images may be taken of your bodily structures. This can be done with:
- CT scan
- MRI scan
- Magnetic resonance angiography (MRA)
- CT angiogram (CTA)
- Doppler ultrasound
Blood tests can also help identify clotting problems in the blood. The fluid that surrounds your brain and spine may be examined.
Immediate treatment is needed to:
- Dissolve or remove a clot (for ischemic stroke)
- Stop bleeding (for hemorrhagic stroke)
Medical Drug Therapy
For an ischemic stroke, the doctor may give medications to:
- Dissolve clots and/or prevent new ones from forming
- Thin blood
- Control blood pressure
- Reduce brain swelling
- Treat an irregular heart rate
For a hemorrhagic stroke, the doctor may give medications to:
- Work against any blood-thinning drugs you were taking before the stroke
- Reduce how your brain reacts to bleeding
- Control blood pressure
- Prevent seizures
For an ischemic stroke, the doctor may do surgery to:
- Reroute blood supply around a blocked artery
- Remove fatty deposits from a carotid artery (carotid artery endarterectomy)
- Widen and keep open a carotid artery (angioplasty and stenting)
- Remove the clot or deliver clot-dissolving medication
A catheter may also be passed through the blood vessels to the blocked area. The catheter can help remove the clot or deliver medication directly to the area.
For a hemorrhagic stroke, the doctor may:
- Remove a piece of the skull to relieve pressure on the brain (craniotomy)
- Place a clip or a tiny coil in an aneurysm to stop it from bleeding
A rehabilitation program focuses on:
- Physical therapy – to regain as much movement as possible
- Occupational therapy – to assist in everyday tasks and self-care
- Speech therapy – to improve swallowing and speech challenges
- Psychological therapy – to improve mood and decrease depression
Many of the risk factors for stroke can be changed. Lifestyle changes that can help reduce your chance of getting a stroke include:
- Exercise regularly.
- Eat more fruits, vegetables and whole grains. Limit dietary salt and fat.
- If you smoke, talk to your doctor about ways to quit.
- Increase your consumption of fish.
- Drink alcohol only in moderation. This means one to two drinks per day.
- Maintain a healthy weight.
- Check your blood pressure frequently. Follow your doctor's recommendations for keeping it in a safe range.
- Take aspirin if your doctor says it is safe.
- Keep chronic medical conditions under control. This includes high cholesterol and diabetes.
- Talk to your doctor about the use of statins. These types of drugs may help prevent certain kinds of strokes in some people.
- Seek medical care if you have symptoms of a stroke, even if symptoms stop.
- If you use drugs, talk to your doctor about rehabilitation programs.