Cerebrovascular accident

I. Introduction

Definition:
Cerebrovascular accident is sudden death of some brain cells due to lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain. It also refers to the injury to the brain that occurs when flow of blood to brain tissue is interrupted by a clogged or ruptured artery, causing brain tissue to die because of lack of nutrients and oxygen. A CVA is also referred to as a stroke.
TYPES OF CVA:
1. Ischemic stroke which refers to the loss of oxygen and nutrients for brain cells that occurs because the blood supply to a portion of the brain has been cut off. Ischemic strokes account for approximately 80% of all strokes, and can be further broken down into two subtypes: thrombotic, also called cerebral thrombosis, and embolic, also termed cerebral embolism.

a. Thrombotic strokes are by far the more prevalent of ischemic strokes, and can be seen in nearly all aging populations worldwide. As people grow older, atherosclerosis, or hardening of the arteries, occurs. This results in a buildup of a waxy, cholesterol-laden substance in the arteries, which eventually narrows the interior space, or lumen, of the artery. This arterial narrowing occurs in all parts of the body, including the brain. As the process continues, the occlusion, or shutting off, of the artery eventually becomes complete so that no blood supply can pass through. Usually the occurrence of the symptoms of a thrombotic stroke are much more gradual and less dramatic than other strokes due to the slow, ongoing process that produces it.

* Transient ischaemic attack (TIA) or ‘mini-stroke’ is a short-term stroke that lasts for less than 24 hours. It is one form of thrombotic stroke, and usually the least serious. TIAs represent the occlusion of a very small artery, or arteriole. The oxygen supply to the brain is quickly restored and symptoms disappear. A transient stroke needs prompt medical attention because it indicates a serious risk of a major stroke.

b. Embolic stroke is a blood clot that forms elsewhere in the body before travelling through the blood vessels and lodging in the brain. In the brain, it starve cells of oxygen. An irregular heartbeat or recent heart attack may make you prone to forming blood clots.

2. Cerebral hemorrhage is when a blood vessel bursts inside the brain and bleeds (hemorrhages). With a hemorrhage, blood seeps into the brain tissue and causes extra damage. Hemorrhagic strokes occur when an artery to the brain has a weakness and balloons outward, producing an aneurysm. Such an aneurysm often ruptures due to this inflation and thinning of the arterial wall, causing a hemorrhage in the affected portion of the brain.
Percentage:
CVA is the leading cause of adult disability in the world. Strokes can and do occur at any age, three-quarters of strokes occur in people over the age of 65 and nearly one fourth of strokes occur in people under the age of 65.. Each year, approximately 795,000 people suffer a stroke, about 600,000 of these are first attacks, and 185,000 are recurrent attacks. Strokes affect men more often than women, although women are more likely to die from a stroke.
Signs and Symptoms:
The symptoms of stroke depend upon the part of the brain that is affected, and how large a portion of brain tissue has been damaged by the CVA. The most common signs of a stroke are:
* weakness down one side of the body, ranging from numbness to paralysis that can affect the arm and leg
* weakness down one side of the face, causing the mouth to droop
* speech may be difficult or become difficult to understand
* swallowing may be affected
* loss of muscle coordination or balance
* brief loss of vision
* severe headache
* confusion
Face-arm-speech test (FAST)
The Stroke Association says three simple checks can help you recognise whether someone has had a stroke or mini-stroke.
* Facial weakness: can the person smile? Has the mouth or eye drooped?
* Arm weakness: can the person raise both arms?
* Speech problems: can the person speak clearly and understand you?
* Test these symptoms.
II. Anatomy and Physiology
Anatomy of cerebral circulation

Arterial supply of oxygenated blood.

Four major arteries and their branches supply the brain with blood. The four arteries arecomposed of two internal carotid arteries (left and right) and two vertebral arteries thatultimately join on the underside (inferior surface) of the brain to form the arterial circle of Willis, or the circulus arteriosus.

The vertebral arteries actually join to form a basilar artery. It is this basilar artery that joins with the two internal carotid arteries and their branches to form the circle of Willis.Each vertebral artery arises from the first part of the subclavian artery and initiallypasses into the skull via holes (foramina) in the upper cervical vertebrae and theforamen magnum. Branches of the vertebral artery include the anterior and posterior spinal arteries, the meningeal branches, the posterior inferior cerebellar artery, and themedullary arteries that supply the medulla oblongata.

III. Pathophysiology

CVA
Predisposing factors: Precipitating factors:
Hypertension Lifestyle(sedentary)
Hyperlipidemia Vices(alcohol,smoke)
DM Vasoconstriction Age
Heart Diseases Diet
Atherosclerosis Heredity
Arteriosclerosis Blockage of blood vessel Sex
Thrombus Self-medication

Lack of oxygen and nutrients supply

Cerebral Ischemia Hypoxia

Cell death Altered cerebal metabolism
Decreased O2 Level
Decreased cerebral perfusion STROKE
Intracerebral
hemorrhage
Local acidosis
Paralysis
Cytotoxic edema

Aneurysm rupture

Brain tissue necrosis

DEATH
IV. Treatment

1. Emergency treatment:

Brain scans are needed to find out what type of stroke you’ve had.

* If a blood clot is the cause, ‘clot busting’ medication may be used to dissolve the clot, but this must be given within three hours of the stroke. Anti-clotting medication such as aspirin may also be given to stop the stroke from getting worse.
* Anti-clotting medication is not given in strokes caused by hemorrhaging because it will make the bleeding worse.
* Tests on key functions like swallowing and movement
* Checks on oxygen, glucose and blood pressure levels.
* If swallowing is affected, you may be fed by a tube or given fluids into a vein (intravenously) to avoid food going into the lungs.
* Emergency treatment of hemorrhagic stroke is aimed at controlling intracranial pressure. Intravenous urea, or mannitol, plus hyperventilation are the most common treatment. Corticosteroids may also be used. Patients with bleeding disorders such as those due to anti- coagulant treatment should have these disorders reversed, if possible.
* Sometimes surgical removal of a clot obstructing an artery is necessary. Hemorrhagic stroke can cause a buildup of pressure on the brain that must be relieved as quickly as possible to prevent further brain damage. In extreme cases, this may require an incision through the skull to relieve the pressure. Surgery for hemorrhage due to aneurysm may be performed if the aneurysm is close enough to the cranial surface to allow access. Ruptured vessels are closed off to prevent bleeding. For aneurysms that are difficult to reach surgically, endovascular treatment may be used. In this procedure, a catheter is guided from a larger artery up into the brain to reach the aneurysm. Small coils of wire are discharged into the aneurysm.