Brain Ischemia Types and Causes

Brain ischemia, also known as cerebral ischemia or cerebrovascular ischemia, occurs when there is an insufficient amount of blood flow to the brain. Oxygen and vital nutrients are carried in the blood through arteries—the blood vessels that carry oxygen and nutrient-rich blood to every part of the body.

The arteries that provide blood to the brain follow a certain pathway that ensures every region of the brain is adequately supplied with blood from one or more arteries. When an artery in the brain becomes blocked or bleeds, this leads to a lower oxygen supply to the region of the brain that relies on that particular artery.

Even a temporary deficit in oxygen supply can impair the function of the oxygen-deprived region of the brain. In fact, if the brain cells are deprived of oxygen for more than a few minutes, severe damage can occur, which may result in the death of the brain tissue. This type of brain tissue death is also known as a cerebral infarction or ischemic stroke.

Brain Ischemia Symptoms

The symptoms of brain ischemia can range from mild to severe. They can last from a few seconds to a few minutes. If the ischemia is brief and resolves before permanent damage (infarction) can occur, then the event is often referred to as a transient ischemic attack (TIA).

If the brain becomes damaged as a result of ischemia, the symptoms may become permanent. Symptoms of brain ischemia include the following:

• Body weakness on one or both sides of the body
• Loss of sensation on one or both sides of the body
• Confusion or disorientation
• Changes in vision of one or both eyes
• Dizziness, vertigo
• Double vision
• Slurred speech
• Loss of consciousness or decreased consciousness
• Balance problems and problems with coordination

Types 

Brain ischemia can be categorized into a few different types. These include:

• Thrombotic: This type of ischemia is caused by blockage of a blood vessel, usually due to a blood clot or a sudden spasm of an artery.
• Embolic: This type of ischemia is typically caused by a blood clot that may have formed in the heart or an artery that then travels to another (often smaller) artery, causing a blockage in the destination artery.
• Hypoperfusion: This type is caused by an overall lack of blood supply. A heart attack, severe blood loss from trauma, or surgery can cause a decrease in overall blood flow to the brain.

The ischemia can affect a small region of the brain, or it may affect a large region or even the entire brain:

• Focal ischemia is confined to a specific area of the brain. It usually occurs when a blood clot has blocked an artery in the brain. Focal ischemia can be the result of a thrombus or embolus.
• Global ischemia affects a wider area of the brain and usually occurs when the blood supply to the brain has been drastically reduced or stops. This is typically caused by a cardiac arrest.

Causes and Risk Factors

Brain ischemia is linked to many different diseases or irregularities. They may include the following:

• Sickle cell anemia or other blood diseases
• Malformed blood vessels
• Arterial plaque buildup
• Congenital heart defects
• Heart disease
• Blood clots
• Irregular heartbeat
• Low blood pressure
• Heart attack
• Ventricular tachycardia

Risk factors for ischemic stroke include:

• High blood pressure
• Smoking tobacco
• Obesity
• High cholesterol
• Diabetes
• Previous TIA
• Atrial fibrillation

Prevention and Treatment

Brain ischemia can be prevented. The treatment of brain ischemia includes a number of medications that are used for the treatment and prevention of ischemic stroke.

Prevention of brain ischemia includes medications that can help you achieve your ideal blood pressure, as well as medications for lowering levels of cholesterol and fat in the blood. Dietary modification can also help in achieving ideal cholesterol levels.

Treatment for sudden ischemia includes the intravenous medication alteplase (tPA). When administered within three hours of diagnosis, this emergency treatment has been shown to improve the medical outcome after a stroke. Sometimes, tPA can be given up to 4.5 hours after stroke symptoms start.

This drug restores blood flow by dissolving the blood clot causing the stroke. There are also emergency endovascular procedures in which the doctor can directly treat the blocked blood vessel.

Sometimes, after a stroke, survivors are at higher risk of developing post-stroke seizures. Anti-seizure medications can help prevent some post-stroke seizures and can also control post-stroke seizures if they do develop.