Neurosciences

What is Stroke?

A stroke, frequently called a “brain attack,” can happen to anyone at any time. Stroke occurs when blood flow to an area of the brain is cut off. Once a stroke happens, brain cells cannot get oxygen and start to die within minutes. A stroke can cause lasting brain damage, long-term disability, or even death.

There are two types of stroke – Ischemic and Hemorrhagic:

Image of Brain Stroke Types and the Brain

1. Ischemic Strokes (Clots): In everyday life, blood clotting is beneficial. When you are bleeding from a wound, blood clots work to slow and eventually stop the bleeding. In the case of stroke, however, blood clots are dangerous because they can block arteries and cut off blood flow to the brain, a process called ischemia thus ischemic stroke. High blood pressure is the number one cause for this type of stroke and about 87% of all strokes are ischemic strokes. An ischemic stroke can occur in two ways: embolic and thrombotic strokes.

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Embolic Stroke

In an embolic stroke, a blood clot forms somewhere in the body (usually the heart) and travels through the bloodstream to your brain. Once in your brain, the clot eventually travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke. The medical word for this type of blood clot is embolus.
Thrombotic Stroke

In the second type of blood-clot stroke, blood flow is impaired because of a blockage to one or more of the arteries supplying blood to the brain. The process leading to this blockage is known as thrombosis. Strokes caused in this way are called thrombotic strokes since a clot that forms on a blood-vessel deposit is called a thrombus.

Blood-clot strokes can also happen as the result of unhealthy blood vessels clogged with a buildup of fatty deposits and cholesterol. Your body regards these buildups as multiple, tiny and repeated injuries to the blood vessel wall. Your body reacts to these injuries just as it would if you were bleeding from a wound; it responds by forming clots. Two types of thrombosis can cause stroke: large vessel thrombosis and small vessel disease (or lacunar infarction).
Large Vessel Thrombosis

Thrombotic stroke occurs most often in the large arteries, so large vessel thrombosis is the most common and best-understood type of thrombotic stroke. Most large vessel thrombosis is caused by a combination of long-term atherosclerosis (narrowing of arteries due to plaque buildup) followed by rapid blood clot formation. Thrombotic stroke patients are also likely to have coronary artery disease, and heart attack is a frequent cause of death in patients who have suffered this type of brain attack.
Small Vessel Disease/Lacunar Infarction

Small vessel disease, or lacunar infarction, occurs when blood flow is blocked to a very small arterial vessel. The term's origin is from the Latin word lacuna, which means hole, and describes the small cavity remaining after the products of deep infarct have been removed by other cells in the body. Little is known about the causes of small vessel disease, but it is closely linked to hypertension (high blood pressure).

2. Hemorrhagic Strokes (Bleeds): Strokes caused by the breakage (hemorrhage) or "blowout" of a blood vessel in the brain are called hemorrhagic strokes. Hemorrhages can be caused by a number of disorders, which affect the blood vessels, including long-standing high blood pressure and cerebral aneurysms. An aneurysm is a weak or thin spot on a blood vessel wall. These weak spots are usually present at birth. Aneurysms develop over a number of years and usually don't cause detectable problems until they break. There are two types of hemorrhagic stroke: subarachnoid and intracerebral.

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Subarachnoid Hemorrhage

An aneurysm bursts in a large artery on or near the thin, delicate membrane surrounding the brain. Blood spills into the area around the brain, which is filled with a protective fluid, causing the brain to be surrounded by blood-contaminated fluid.
Intracerebral Hemorrhage

Bleeding occurs from vessels within the brain itself. Hypertension (high blood pressure) is the primary cause of this type of hemorrhage.

Frequently Asked Questions

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Q: Is stroke due to overwork or stress?

A: No. Almost everyone who has ever had a stroke may have been under stress or have been overworking at some time before the onset of the stroke. It is natural to think of stroke and stress as being related but they are not related.
Q: Does stroke affect the heart?

A: No. The stroke itself has no effect on the heart, but patients who suffer a stroke may have had heart disease already, which they may or may not have known about before the stroke.
Q: Will recovery occur and how long will it take?
A: Partial recovery is very usual, but total recovery is less common. After a stroke four things may happen:
1. The brain cells which were badly damaged at the onset die and never recover.
2. Other cells which were only partially damaged, due to swelling of the brain, recover and start working again. This process takes place during the first few weeks after the onset of the stroke.
3. Parts of the brain which are unaffected by the stroke begin to take over the functions of the dead parts. This can occur only to a limited extent, but may continue for a long time.
4. The patient adapts to the loss of function and learns new ways of living with the damaged brain.
Q: What are the risks of having a second stroke?

A: Having a stroke does not automatically mean you will have another stroke. However, the conditions which caused the first stroke- (weakness of an artery wall or blood clotting) sometimes cannot be reversed so the possibility of a second stroke is high. You can help reduce your chances having a second stroke by controlling risk factors and making healthy lifestyle choices.
Q: How is movement affected?

At the onset of stroke, the muscles of the face, trunk, arm and leg on either the left or right side of the body are weak and relaxed. In most cases the power gradually returns, first to the leg and then to the arm. However, unless the limbs are placed in the correct position and are frequently put through a range of movements, there is a danger that they may stiffen, so that, even if the power returns, the limbs could be practically useless. This is why it is important to place the limbs in the correct position allowing recovery to take place in the best way. The simple rule is to let the leg bend but to keep the arm straight. It is also vital to treat the body as a whole, not just the paralyzed limbs in isolation.
Q: How is speech affected?

A: Speech is affected in two ways. In some patients, speech is slurred and indistinct or even completely absent, but the patient can read, write and understand perfectly what is said. This condition is called dysarthia, and treatment usually helps with the patient’s recovery.

The other condition is much more complex. It is called dysphasia or aphasia and is due to damage to the part of the brain which controls all language processes. This can affect the patient's ability to speak, understand speech, read and write. Recovery from dysphasia can be rapid and complete, but is, in most cases, slow and incomplete, and patients and their relatives need a great deal of help from speech and language therapists and others.
Q: How is vision affected?

A: In most stroke cases, vision is not affected. Patients who complain of visual difficulty, the fault is not in the eyesight itself, but in the interpretation by the brain of what the eye sees. In most people, the two sides of the brain each form a separate picture of half of what lies before it, and the two pictures are joined together to give a total view. When part of the brain forming one of those half pictures is damaged by a stroke, the patient sees only one half of the world depending on which half of the brain is affected. This can be perplexing for the patient and relatives, and is very disabling, but recovery, although slow, usually occurs.