Strokes: The Basics

Featured Article, Healthy Heart, Stroke
on August 13, 2011
Think Stock

The brain thrives on a rich supply of blood, nutrients and oxygen. Every move, decision, response and stimulus of the body depends upon the brain — no matter how complex or primitive the organism. From gnats to gnus, chimpanzees to humans, we all are alike in that we rely on the brain in order to function. Know the kinds of strokes and their causes in order to protect this complex and vital organ.

Strokes can destroy the brain. A stroke impedes or stops the blood supply to the brain. Any disruption in the flow of blood to the brain damages and kills brain tissue. A stroke is a medical emergency. If a stroke is suspected, get to the ER as quickly as possible. Any delay in treatment can cause permanent neurological damage, complications and even death.

There are two types of stroke ischemic and hemorrhagic. Both types are very dangerous and their causes vary. Overall, most strokes are the ischemic type. The Mayo Clinic states that ischemic strokes account for almost 90 percent of all strokes.

Ischemic strokes occur when arteries are impinged. The reduced blood flow — ischemia — causes brain cells to die in minutes. There are two categories of ischemic strokes:

  • Thrombotic stroke occurs when a thrombus (blood clot) is formed in an artery, such as the carotid artery, that supplies blood to the brain. Typically, clots such as this will form in areas that are already damaged by atherosclerosis — fatty plaque deposits.
  • Embolic stroke occurs when a blood clot or other debris forms in a blood vessel away from the brain, but travels through the body and lodges in one of the narrow brain arteries. Atrial fibrillation — irregular heartbeats — leads to a pooling of blood in the heart, thus forming these types of clots.

Hemorrhagic strokes result from a bleed in the brain. Leaks or ruptures of blood vessels can be the result of hypertension, aneurysms (weak spots in blood vessel walls). Rarely, an anomalous tangle of blood vessels — that is present from birth — causes a rupture. There are two kinds of hemorrhagic stroke:

  • Intracerebral hemorrhage refers to a burst blood vessel in the brain. The pooling of blood damages brain cells. Tangential cells are also damaged by the reduction in blood supply due to the hemorrhage. Often, high blood pressure causes the small arteries to become brittle and more likely to crack or rupture.
  • Subarachnoid hemorrhage occurs when arterial bleeding, likely from an aneurysm developed at birth or over time, is so near the surface of the brain that the pooling blood fills a space between the skull and the brain itself. Vasospasms, where the blood vessels widen and narrow irregularly, cause further damage by limiting the brain’s blood flow even more. A sudden and severe headache may signal this type of hemorrhage.

With strokes, mini does not mean harmless. Transient ischemic attacks are also known as ministrokes. These brief episodes of five minutes or less are due to a temporary decrease in blood supply to the brain. Debris or clots are the culprits, most often. Even if symptoms seem to go away, medical care must be sought. The risk of a full-blown stroke is high with ministrokes. Symptoms are not always definitive, even when the stroke is causing brain damage. Your highly trained ER physician is best able to manage any kind of stroke, mini or otherwise.