Stroke Cerebrovascular Accident PDF

Stroke Cerebrovascular Accident Marina Gharibian Adra PhD RN NURS 210B Spring 2023-2024  Cerebral Circulation  Anatomy and Physiology  The blood flow to the brain is supplied by the two internal carotid arteries anteriorly and the vertebral arteries posteriorly....

Stroke Cerebrovascular Accident Marina Gharibian Adra PhD RN NURS 210B Spring 2023-2024  Cerebral Circulation  Anatomy and Physiology  The blood flow to the brain is supplied by the two internal carotid arteries anteriorly and the vertebral arteries posteriorly.  The internal carotid artery, branches into several arteries: ophthalmic, posterior communicating, choroidal, anterior cerebral, and middle cerebral. The two vertebral arteries arise from the subclavian artery. They enter the skull through the foramen magnum and unite to form the basilar artery. Branches of the basilar and vertebral arteries supply the medulla, pons, cerebellum, midbrain, and caudal part of the diencephalon. The distal branches of the internal carotid and vertebral arteries communicate at the base of the brain through the Circle of Willis; this anastomosis of arteries can provide continued circulation if blood flow through one of the main vessels is disrupted.  Stroke Stroke (or Brain Attack) is an acute neurologic deficit from a vascular disorder that injurs brain tissue. Stroke remains one of the leading causes of mortality and morbidity in the United States. Types of Stroke  There are two main types of strokes: ischemic stroke and hemorrhagic stroke. Ischemic/Hemorrhagic Stroke Ischemic strokes are caused by an interruption of blood flow in a cerebral vessel and are the most common type of stroke, accounting for 70% to 80% of all strokes. The less common hemorrhage strokes are caused by bleeding into brain tissue. This type of stroke usually is from a blood vessel rupture caused by hypertension, aneurysms, head injury, and has a much higher fatality rate than ischemic strokes.  Among the major risk factors for stroke are:  age  sex  race  heart disease Risk Factors  hypertension  high cholesterol levels  cigarette smoking  prior stroke  diabetes mellitus  excess alcohol use  sedentary lifestyle.  Ischemic Strokes Ischemic strokes are caused by cerebrovascular obstruction by THROMBOSIS or EMBOLI.  A common classification system identifies 5 stroke subtypes and their frequency: ✪ Large artery atherosclerotic disease (both thrombosis and arterial emboli) 20%. ✪ Small vessel or penetrating artery disease (lacunar stroke) 25%. ✪ Cardiogenic embolism 20%. ✪ Cryptogenic stroke (undetermined cause) 30%. ✪ Unusual cause: example Migraine 5%. Ischemic Penumbra in Evolving Stroke During the evolution of a stroke, there usually is a central core of dead or dying cells, surrounded by an ischemic area of minimally perfused cells called the penumbra (i.e., halo). Whether the cells of the penumbra continue to survive depends on the successful return of adequate circulation and the volume of toxic products released by the neighboring dying cells. Oligemia: hypo perfused parenchyma with a cerebral blood flow (CBF) value of approximately 22–60 mL/100 g/min, which is above the ischemic threshold (22 mL/100 g/ min). Core represents the irreversibly injured tissue. Diffusion abnormality theoretically represents an irreversibly injured tissue but if reperfusion is administered fast this area might recover. Perfusion area represents the area of viable by threatened brain tissue which is surrounded by benign oligemia. Hemorrhagic Stroke The most frequently fatal stroke is a spontaneous hemorrhage into the brain substance. With rupture of a blood vessel, hemorrhage into the brain tissue occurs, resulting in edema, compression of the brain contents, or spasm of the adjacent blood vessels. The most common predisposing factors are advancing age and hypertension. Other causes of hemorrhage are aneurysm, trauma, drugs. Hemorrhagic Stroke A cerebral hemorrhage occurs suddenly, usually when the person is active. Vomiting commonly occurs at the onset, and headache sometimes occurs. In the most common situation, hemorrhage into the basal ganglia results in contralateral hemiplegia. The hemorrhage and resultant edema exert great pressure on the brain substance, and the clinical course progresses rapidly to coma and frequently to death. If you think someone may be having a stroke, act F.A.S.T. and do the following test: F—Face: Ask the person to smile. Does one side of the face droop? A—Arms: Ask the person to raise both arms. Does one arm drift downward? S—Speech: Ask the person to repeat a simple phrase. Is the speech slurred or strange? T—Time: If you see any of these signs, call 9-1-1 right away. Transient ischemic attack-TIA  Transient ischemic attacks are characterized by ischemic cerebral neurologic deficits that last for less than 24 hours.  TIA or ministroke is equivalent to brain angina and reflects a temporary disturbance in cerebral blood flow, which reverses before infarction occurs, analogous to angina in relation to heart attack.  TIAs are important because they may provide warning or impending stroke.  In fact, the risk of stroke after a TIA is maximal immediately after the event.