Friday, August 01, 2014

Definition

A stroke occurs when the arterial blood flow leading to or in the brain becomes blocked or ruptures.

Blood carries oxygen and nutrients to the neurons (nerve cells) in the brain, so when the blood flow stops, the cells begin to die. As a result, the functions of the body controlled by the nerve cells can lose their ability to function.

Description

The specific abilities that will be lost or affected by the stroke depend on the extent of the cell death and where in the brain the stroke happened.

The brain is divided into four primary parts: the right hemisphere, the left hemisphere, the cerebellum and the brain stem.

The right hemisphere controls:

  • left side of the body
  • analytical and perceptual tasks such as judging distance, size, speed, position
  • short-term memory

The left hemisphere controls:

  • right side of the body
  • speech and language
  • memory

The cerebellum controls:

  • balance and coordination

The brain stem controls:

  • life-support functions such as breathing, blood pressure and heartbeat
  • eye movements
  • hearing
  • speech
  • swallowing

Depending on the severity of the stroke, victims may or may not experience any or all losses of the above functions.

Causes

There are two broad categories of strokes, called ischemic stroke or hemorrhagic stroke.

Ischemic stroke is caused by a blockage of a blood vessel in the brain or neck. This stroke can stem from three different conditions: thrombosis, embolism or stenosis:

  • Thrombosis (cerebral thrombosis) is the formation of a clot within a blood vessel of the brain or neck and is usually caused by atherosclerotic plaque build-up.
  • Embolism (cerebral embolism) is the movement of a clot from another part of body to the brain or neck. These clots can form on artificial valves in the heart, on atherosclerotic plaques in aorta or caused from a condition called atrial fibrillation. Atrial fibrillation is an irregular heartbeat whereby the upper chamber of the heart quivers rapidly rather than beats. Because this quivering motion is not forceful enough to send all the blood to the heart's lower chambers, the blood pools, thus allowing clots to develop.
  • Stenosis is a severe narrowing of an artery in or leading to the brain. Roughly 2/3 of all strokes are caused by clots.

Hemorrhagic stroke is the bleeding into the brain or the spaces surrounding the brain which is caused by a number of disorders that affect the blood vessels (i.e., high blood pressure and cerebral aneurysm). There are two types of hemorrhagic stroke: subarachnoid and intracerebral.

  • ubarachnoid hemorrhage is caused by the rupture of a blood vessel on the surface of the brain so that blood fills the space between the brain and the skull.
  • An intracerebral hemorrhage is caused by the rupture of a blood vessel within the brain itself.

Some factors that increase the risk of stroke are genetically determined, others are simply a function of natural processes, and still others result from a person's lifestyle. The factors resulting from heredity or natural processes can't be changed, but those that are environmental can be modified with a doctor's help.

There are five uncontrollable risk factors:

  • Age - your chances of having a stroke go up as you get older. Two-thirds of all strokes happen to people over age 65. Your stroke risk doubles with each decade past age 55.
  • Sex - males have a slightly higher risk than females.
  • Race - American blacks have a higher stroke risk than most other racial groups.
  • Family history of diabetes.
  • Family history of stroke or TIA (transient ischemic attack).

There are two basic controllable risk factors:

  • Treatable medical disorders - includes diabetes, atrial fibrillation, heart attack, high blood pressure, high cholesterol, carotid artery disease, heart disease, personal history of stroke or TIA and patent foramen ovale (PFO). PFO is an abnormal opening between the right and left sides of the heart.
  • Lifestyle factors - includes smoking, drinking too much, obesity, drug abuse (especially cocaine), physical inactivity and low estrogen.

Symptoms

The warning signs of stroke are:

  • Sudden weakness or numbness of the face, arm and leg on one side of the body.
  • Loss of speech, or trouble talking or understanding speech.
  • Dimness or loss of vision, particularly in only one eye.
  • Unexplained dizziness, unsteadiness or sudden falls.
  • "Temporary strokes" (transient ischemic attacks or TIAs). These can occur days, weeks or even months before a major stroke. TIAs result when a blood clot temporarily clogs an artery and part of the brain does not get the supply of blood it needs. The symptoms occur rapidly and last a relatively short period of time, usually from a few minutes to several hours. The usual symptoms are like those of a full-fledged stroke, except that the symptoms of a TIA are temporary, lasting 24 hours or less. In fact, people who have had TIAs are 9.5 times more likely to have a stroke than people of the same age and sex who have not had a TIA.

Treatment

Treating a stroke depends on where the stroke occurred in your brain and whether it's ischemic or hemorrhagic. The doctor may use a magnetic resonance imaging (MRI) scan, computed tomography (CT) imaging or angiography (injecting dye through a catheter inserted into the suspected blocked blood vessel and taking x-rays of the vessels) to determine the stroke type and location.

Time is critical. Until a few years ago, strokes were regarded as untreatable. Brain cells were thought to die within minutes after a stroke began, so stroke treatment was believed useless. The only onsite medical treatment is stabilization and "wait and see." Now researchers have discovered that some brain cells die immediately after a stroke, but others can survive for as long as several days. It is now clear that treatment following a stroke, especially if begun within three hours of onset, can help preserve brain tissue.

In June 1996 the FDA approved tissue plasminogen activator (t-PA) as the first treatment for strokes caused by arterial blockages. This "clotbuster" is inserted into the femoral artery near the groin and then threaded up into the brain to directly dissolve the blood clot, thereby limiting or stopping the damage to the brain cells. This therapy is used on ischemic strokes and effective within three hours of onset.

The use of t-PA is not recommended after three hours of onset due to the risk of hemorrhaging, thus standard treatment is administered. In an ischemic stroke the goal is to (1) maintain normal blood pressure and (2) improve blood flow by preventing recurrent clots. This is done by administrating anti-hypertensives to reduce blood pressure, platelet-inhibiting drugs such as aspirin, ticlopidine (Ticlid) or an anticoagulant such as heparin, coumadin or warfarin to prevent blood clots from forming or growing.

If unsuccessful, a carotid endarterectomy may be considered. This procedure removes the atherosclerotic plaque and the blood clot from the left or right carotid artery (the major vessels that carry blood through the neck to the brain) thus allowing the blood to flow uninterrupted.

In a hemorrhagic stroke, the goal is to (1) get the blood pressure under control and (2) correct the cause of the hemorrhage and protect the brain from further damage. The hemorrhage causes blood to pool in the brain and thus increases pressure on the brain. The doctor will give diuretic drugs to minimize the temporary swelling of the brain tissue.

Rarely is surgery recommended, but if tests detect an aneurysm, the surgeon may clamp the aneurysm at its base and then remove it. The surgeon now has the option to use a catheter, containing a metal coil, that passes through the blood vessel in the neck. The metal coil causes the aneurysm to clot and seal itself off.

Some people are only slightly affected by strokes. Others recover quickly from what seemed like a severe stroke. Still others may suffer such serious damage that it will take a long time to regain even partial use of their limbs, speech, or whatever faculties that have been affected.

Successful rehabilitation depends on the extent of brain damage, the patient's attitude, the skill of the rehabilitation team, and the cooperation of family and friends. Most stroke patients can benefit from rehabilitation, and today the outlook for stroke patients is more hopeful than ever before. Because of advances in treatment and rehabilitation, many patients are being restored to a fully functional life.

For rehabilitation to be most effective, three points must be kept in mind:

1. Rehabilitation must begin as soon after the stroke as possible

2. The family can be the patient's most important means of support during the rehabilitation process

3. Rehabilitation is a team effort with the physician, nurse, and other specialists working with the patient and their family.

Questions

What are the chances the symptoms were caused by something other than a stroke?

What was the cause of the stroke?

What tests are used to determine what type of stroke occurred and how much damage was done?

What medications will be prescribed? What are the side effects?

Would surgery be recommended to improve cerebral circulation? If so, what type of surgery?

What other treatment can be used to prevent another stroke?

Is there a support group for the family to go to ask questions?

What are the chances of having a stroke after a TIA or having another stroke after a first?

What do we need to know about rehabilitation?

Can the rehabilitation be done on an outpatient basis?

Will a nurse or therapist help instruct us on what we need to know for home care such as exercise, diet and communication?

Approximately how long will rehabilitation take to return to normal activities?

Prevention

Strokes may be prevented by lowering your blood pressure, quitting smoking, beginning or increasing exercise, controlling medical problems with medications (i.e., atrial fibrillation requires anticoagulants), maintaining optimal weight, and eating a diet high in fruits and vegetables.

If you have a blocked carotid artery your doctor may suggest a carotid endarterectomy to remove the fatty deposits.