Stroke 101

Cerebrovascular disease or stroke is the loss or alteration of body functions that results from an insufficient supply of blood to some parts of the brain. For human brain to function at peak levels, blood must flow through its many vessels. If the blood flow is obstructed for more than several minutes, injury to the brain cells becomes permanent and tissue dies in the affected region.

Stroke is one of the leading causes of disability. It can lead to weakness or paralysis usually of one side of the body. Often, the person has slurring of speech or even inability to talk (aphasia). Of course, if stroke is massive and severe, death becomes inevitable.

If we consider an isolated blood vessel, blood flow to the brain tissue can be hampered in two ways: 1) the vessel clogs within (ischemic stroke); and 2) the vessel ruptures, causing blood to leak into the brain (hemorrhagic stroke).

Ischemic strokes accounts for about 85% of all cases. It occurs as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis. These fatty deposits can cause two types of obstruction - cerebral thrombosis and cerebral embolism.

Cerebral thrombosis refers to a thrombus (blood clot) that develops at the clogged part of the vessel. This is usually seen in older people and may occur in a person at rest.

Cerebral embolism refers generally to a blood clot that forms at another location in the circulatory system, usually the heart and large arteries of the upper chest and neck. A portion of the blood clot breaks loose, enters the bloodstream and travels through the brain’s blood vessels until it reaches vessels too small to let it pass. A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation. It creates conditions where clots can form in the heart, dislodge and travel to the brain. The onset of cerebral embolism is usually sudden.

On the other hand, hemorrhagic stroke accounts for 15% of all cases. It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue. It may either cause intracerebral hemorrhage or subarachnoid hemorrhage.

Hemorrhagic stroke occurs when a weakened blood vessel ruptures. The two types of weakened blood vessels that usually cause hemorrhagic stroke are aneurysms and arteriovenous malformations (AVMs).

An aneurysm is a ballooning of a weakened region of a blood vessel. If left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain. Meanwhile, an arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels. Any one of these vessels can rupture, also causing bleeding into the brain.

Another important condition is the transient ischemic attacks or TIAs, which are considered minor or warning strokes. In a TIA, conditions indicative of an ischemic stroke are present and the typical stroke warning signs develop. However, the obstruction (blood clot) occurs for a short time and tends to resolve itself through normal mechanisms.

Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke. Steps should be taken immediately to prevent a stroke.

Stroke is a medical emergency and everyone should know the following warning signs because every second counts:

• sudden numbness or weakness of the face, arm or leg, especially on one side of the body
• sudden confusion, trouble speaking or understanding
• sudden trouble seeing in one or both eyes
• sudden trouble walking, dizziness, loss of balance or coordination; and
• sudden, severe headache with no known cause.

Seek medical attention immediately if these symptoms occur. Time lost is brain lost!

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