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Biological Sciences
Stephen Reid

Chapter 58: Stroke STROKE  Stroke occurs when there is ischemia (inadequate blood flow) to a part of the brain or hemorrhage into the brain that results in death of brain cells. Functions, such as movement, sensation, or emotions, that were controlled by the affected area of the brain are lost or impaired.  The term brain attack is increasingly being used to describe stroke. This term communicates the urgency of recognizing the clinical manifestations of a stroke and treating a medical emergency, similar to what would be done with a heart attack. Risk Factors  The most effective way to decrease the burden of stroke is prevention. Nonmodifiable risk factors include age, gender, race, and heredity.  Hypertension is the single most important modifiable risk factor. Other modifiable risk factors include heart disease, diabetes, increased serum cholesterol, smoking, excessive alcohol consumption, obesity, physical inactivity, poor diet, and drug abuse.  Atherosclerosis (hardening and thickening of arteries) is a major cause of stroke. It can lead to thrombus formation and contribute to emboli.  A transient ischemic attack (TIA) is a temporary focal loss of neurologic function caused by ischemia of one of the vascular territories of the brain, lasting less than 24 hours and often lasting less than 15 minutes. Most TIAs resolve within 3 hours. TIAs are a warning sign of progressive cerebrovascular disease.  Strokes are classified as ischemic or hemorrhagic based on the underlying pathophysiologic findings.  Ischemic stroke: o An ischemic stroke results from inadequate blood flow to the brain from partial or complete occlusion of an artery and accounts for approximately 80% of all strokes. Ischemic strokes are further divided into thrombotic and embolic. o A thrombotic stroke occurs from injury to a blood vessel wall and formation of a blood clot. The lumen of the blood vessel becomes narrowed, and if it becomes occluded, infarction occurs. o Embolic stroke occurs when an embolus lodges in and occludes a cerebral artery, resulting in infarction and edema of the area supplied by the involved vessel.  Hemorrhagic stroke: o Hemorrhagic strokes account for approximately 15% of all strokes and result from bleeding into the brain tissue itself or into the subarachnoid space or ventricles. o Intracerebral hemorrhage is bleeding within the brain caused by a rupture of a vessel. The prognosis of intracerebral hemorrhage is poor. o Subarachnoid hemorrhage occurs when there is intracranial bleeding into the cerebrospinal fluid–filled space between the arachnoid and pia mater membranes on the surface of the brain. Subarachnoid hemorrhage is commonly caused by rupture of a cerebral aneurysm (congenital or acquired weakness and ballooning of vessels). Clinical Manifestations and Diagnostic Studies  A stroke can have an effect on many body functions, including motor activity, bladder and bowel elimination, intellectual function, spatial-perceptual alterations, personality, affect, sensation, swallowing, and communication. o Motor deficits include impairment of (1) mobility, (2) respiratory function, (3) swallowing and speech, (4) gag reflex, and (5) self-care abilities. o The patient may experience aphasia (total loss of comprehension and use of language) when a stroke damages the dominant hemisphere of the brain or dysphasia (difficulty related to the comprehension or use of language) due to partial disruption or loss. o Many stroke patients also experience dysarthria, a disturbance in the muscular control of speech. Impairments may involve pronunciation, articulation, and phonation. o Patients who have had a stroke may have difficulty controlling their emotions. o Both memory and judgment may be impaired as a result of stroke. o Most problems with urinary and bowel elimination occur initially and are temporary.  The single most important diagnostic tool for patients who have experienced a stroke is the noncontrast CT scan. The CT scan indicates the size and location of the lesion and differentiates between ischemic and hemorrhagic stroke. Collaborative Care: Prevention  Measures to prevent the development of a thrombus or embolus are used in patients at risk for stroke. Antiplatelet drugs are usually the chosen treatment to prevent further stroke in patients who have had a TIA related to atherosclerosis.  Surgical interventions for the patient with TIAs from carotid disease include carotid endarterectomy, transluminal angioplasty, stenting, and extracranial-intracranial bypass. Collaborative Care: Acute Phase  The goals for collaborative care during the acute phase are preserving life, preventing further brain damage, and reducing disability. Treatment differs according to the type of stroke and changes as the patient progresses from the acute to the rehabilitation phase.  Elevated BP is common immediately after a stroke and may be a protective response to maintain cerebral perfusion.  Fluid and electrolyte balance must be controlled carefully. The goal generally is to keep the patient adequately hydrated to promote perfusion and decrease further brain injury.  Recombinant tissue plasminogen activator (tPA) administered IV is
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