Stroke
Stroke: Excerpt from Handbook of Diseases
Stroke is a sudden impairment of cerebral circulation in one or more blood vessels supplying the brain. Stroke interrupts or diminishes oxygen supply and commonly causes serious damage or necrosis in brain tissues.
The sooner circulation returns to normal after a stroke, the better the chances are for complete recovery. However, about half of those who survive a stroke remain permanently disabled and experience a recurrence within weeks, months, or years.
Stroke is the third most common cause of death in the United States today and the most common cause of neurologic disability. It affects 500,000 people each year; half of them die as a result.
Causes
Factors that increase the risk of stroke include history of transient ischemic attacks (TIAs), atherosclerosis, hypertension, electrocardiogram changes, arrhythmias, rheumatic heart disease, diabetes mellitus, gout, postural hypotension, cardiac or myocardial enlargement, high serum triglyceride levels, lack of exercise, use of hormonal contraceptives, cigarette smoking, and family history of stroke.
The major causes of stroke are thrombosis, embolism, and hemorrhage.
Thrombosis
In middle-aged and elderly people — among whom there’s a higher incidence of atherosclerosis, diabetes, and hypertension — thrombosis is the most common cause of stroke. Obstruction of a blood vessel causes the stroke. Typically, the main site of the obstruction is the extracerebral vessels, but sometimes it’s the intracerebral vessels.
Thrombosis causes ischemia in brain tissue supplied by the affected vessel as well as congestion and edema. The latter may produce more symptoms than the thrombosis itself, but these subside with the edema.
Thrombosis may develop while the patient sleeps or shortly after he awakens; it can also occur during surgery or after a myocardial infarction. The risk increases with obesity, smoking, or the use of hormonal contraceptives. Cocaine-induced ischemic stroke is now seen in younger patients.
Embolism
The second most common cause of stroke, embolism is an occlusion of a blood vessel caused by a fragmented clot, a tumor, fat, bacteria, or air. It can occur at any age, especially among patients with a history of rheumatic heart disease, endocarditis, posttraumatic valvular disease, or myocardial fibrillation and other cardiac arrhythmias or after open-heart surgery or placement of a mechanical heart valve.
The embolus usually develops rapidly — in 10 to 20 seconds — and without warning. When it reaches the cerebral vasculature, it cuts off circulation by lodging in a narrow portion of an artery, most commonly the middle cerebral artery, causing necrosis and edema.
If the embolus is septic and infection extends beyond the vessel wall, an abscess or encephalitis may develop. If the infection is within the vessel wall, an aneurysm may form, which could lead to cerebral hemorrhage.
Hemorrhage
The third most common cause of stroke is hemorrhage. Like an embolism, it may occur suddenly, at any age. Such hemorrhage results from chronic hypertension or aneurysms, which cause sudden rupture of a cerebral artery. The rupture diminishes blood supply to the area served by this artery. In addition, blood accumulates deep within the brain, further compressing neural tissue and causing even greater damage.
Stroke classification
Strokes are classified according to their course of progression. The least severe is the TIA, or little stroke, which results from a temporary interruption of blood flow, usually in the carotid and vertebrobasilar arteries. A progressive stroke, or stroke-in-evolution (thrombus-in-evolution), begins with slight neurologic deficit and worsens in a day or two. In a completed stroke, neurologic deficits are maximal at onset and don’t progress.
Signs and symptoms
Signs and symptoms of stroke vary, depending on the artery affected (and, consequently, the portion of the brain it supplies), the severity of damage, and the extent of collateral circulation that develops to help the brain compensate for decreased blood supply.
If the stroke occurs in the left hemisphere, it produces symptoms on the right side; if it occurs in the right hemisphere, it produces symptoms on the left side. However, a stroke that causes cranial nerve damage produces signs of cranial nerve dysfunction on the same side as the hemorrhage.
Symptoms are usually classified according to the artery affected:
❑ middle cerebral artery: aphasia, dysphasia, visual field cuts, and hemiparesis on the affected side (more severe in the face and arm than in the leg)
❑ carotid artery: weakness, paralysis, numbness, sensory changes, and visual disturbances on the affected side; altered level of consciousness; bruits; headaches; aphasia; and ptosis
❑ vertebrobasilar artery: weakness on the affected side, numbness around the lips and mouth, visual field cuts, diplopia, poor coordination, dysphagia, slurred speech, dizziness, amnesia, and ataxia
❑ anterior cerebral artery: confusion, weakness and numbness (especially in the leg) on the affected side, incontinence, loss of coordination, impaired motor and sensory functions, and personality changes
❑ posterior cerebral arteries: visual field cuts, sensory impairment, dyslexia, coma, and cortical blindness. Usually, there’s no paralysis.
Symptoms can also be classified as premonitory, generalized, and focal. Premonitory symptoms (such as drowsiness, dizziness, headache, and mental confusion) are rare. Generalized signs and symptoms (such as headache, vomiting, mental impairment, seizures, coma, nuchal rigidity, fever, and disorientation) are typical. Focal symptoms (such as sensory and reflex changes) reflect the site of hemorrhage or infarction and may worsen.
Diagnosis
Confirmation of stroke is based on symptoms, a history of risk factors, and the results of diagnostic tests.
❑ Computed tomography scan shows evidence of hemorrhagic stroke immediately but may not show evidence of thrombotic infarction for 48 to 72 hours.
❑ Magnetic resonance imaging may help identify ischemic or infarcted areas and cerebral swelling.
UNDER STUDY: Positron emission tomography can quantify cerebral blood flow. Single-photon emission tomography, computed tomography perfusion, and magnetic resonance perfusion techniques report relative blood flow and are research tools.
❑ Ophthalmoscopy may show signs of hypertension and atherosclerotic changes in retinal arteries.
❑ Angiography outlines blood vessels and pinpoints atherosclerotic plaques, vessel occlusion, or the rupture site.
❑ EEG helps to localize the damaged area.
Other baseline laboratory studies include urinalysis, coagulation studies, complete blood cell count, serum osmolality, and electrolyte, glucose, triglyceride, creatinine, and blood urea nitrogen levels.
Treatment
Treatment options vary, depending on the type of stroke the patient experiences. Early medical diagnosis of the type of stroke coupled with new drug treatments can greatly reduce the long-term disability secondary to ischemia.
Surgery performed to improve cerebral circulation for patients with thrombotic or embolic stroke includes an endarterectomy (the removal of atherosclerotic plaque from the inner arterial wall) or a microvascular bypass (the surgical anastomosis of an extracranial vessel to an intracranial vessel).
Medications useful in treating stroke include:
❑ alteplase (recombinant tissue plasminogen activator), effective in emergency treatment of embolic stroke (See Restoring ischemic brain tissue with alteplase.) (Patients with embolic or thrombotic stroke who aren’t candidates for alteplase [3 to 6 hours poststroke] should receive aspirin or heparin.)
❑ long-term use of aspirin or ticlopidine, used as antiplatelet agents to prevent recurrent stroke
❑ anticoagulants (heparin, warfarin), which may be required to treat crescendo TIAs not responsive to antiplatelet drugs
❑ antihypertensives, antiarrhythmics, and antidiabetics, which may be used to treat risk factors associated with recurrent stroke.
Special considerations
Early supportive therapy
❑ Frequently assess neurologic status, using the National Institutes of Health (NIH) Stroke Scale to determine deficits. (See Using the NIH Stroke Scale, pages 828 and 829.)
❑ If the patient has been treated with alteplase, monitor him for signs of hemorrhage.
❑ Monitor blood pressure frequently; give labetalol for severe hypertension.
CLINICAL TIP: Remember that because autoregulation is disrupted in patients with stroke, it’s necessary to maintain perfusion higher than the usual blood pressure.
❑ Use acetaminophen and hypothermia blankets to control fever.
❑ Maintain a patent airway and oxygenation status; intubate and ventilate the patient as needed.
❑ Monitor blood glucose levels.
❑ Monitor electrocardiogram results, and treat arrhythmias as early as possible.
❑ If the patient develops a headache, administer an analgesic.
Ongoing care
❑ Watch for signs and symptoms of pulmonary emboli, such as chest pain, shortness of breath, dusky color, tachycardia, fever, and changed sensorium. If the patient is unresponsive, monitor his blood gas levels often, looking for increased partial pressure of carbon dioxide or decreased partial pressure of arterial oxygen.
❑ Watch for signs of other complications, such as infection, cerebral edema, hydrocephalus, seizures, aspiration pneumonia, deep vein thrombosis, pressure ulcers, urinary tract infections, contractures, and subluxation.
❑ Offer the urinal or bedpan every 2 hours. If the patient is incontinent, he may need an indwelling urinary catheter, but this should be avoided, if possible, because of the risk of infection.
❑ Ensure adequate nutrition. Check the patient’s gag reflex before offering small oral feedings of semisolid foods. (A speech pathologist should assess the patient to determine his needs and specific feeding strategies for dysphagia.) Place the food tray within the patient’s visual field. If oral feedings aren’t possible, insert a nasogastric tube.
❑ To prevent aspiration pneumonia, position the patient in an upright, lateral position to allow secretions to drain. Turn the patient frequently.
❑ Position the patient and align his extremities correctly to prevent external rotation. Use high-topped sneakers to prevent footdrop when the patient is sitting up and his feet are on the floor. Avoid subluxation of the affected shoulder through proper support and positioning.
❑ Provide range-of-motion exercises throughout the day. Consult a physical therapist for additional positioning and transfer strategies and splinting devices.
❑ Consult a physical therapist, an occupational therapist, and a speech therapist for short- and long-term rehabilitative care goals. A multidisciplinary approach is necessary to help minimize long-term disability. Deficits can include motor weakness, coordination and balance problems, diminished corneal reflex, visual field deficits, dysarthria, dysphasia, impaired memory and concentration, and pain.
❑ Establish and maintain communication with the patient. If he’s aphasic, set up a simple method of communicating basic needs. Remember to phrase your questions so he’ll be able to answer using this system. Repeat yourself quietly and calmly, and use gestures, if necessary, to help him understand. Even the unresponsive patient can hear, so don’t say anything in his presence you wouldn’t want him to hear and remember.
❑ Provide psychological support. Set realistic short-term goals. Involve the patient’s family in his care when possible, and explain his deficits and strengths.
❑ Establish rapport with the patient. Spend time with him, and provide a means of communication. Simplify your language, asking questions that can be answered with a yes or no whenever possible. Don’t correct his speech or treat him like a child. Remember that building rapport may be difficult because of mood changes that may result from brain damage or as a reaction to being dependent.
❑ If necessary, teach the patient to comb his hair, dress, and wash. With the aid of a physical therapist and an occupational therapist, obtain appliances, such as walking frames, hand bars for the toilet, and ramps, as needed.
❑ If speech therapy is indicated, encourage the patient to begin as soon as possible and follow through with the speech therapist’s suggestions.
❑ To reinforce teaching, involve the patient’s family in all aspects of rehabilitation. With their cooperation and support, devise realistic discharge goals, and let them help decide when the patient can return home.
❑ Before discharge, warn the patient and his family to report any premonitory signs or symptoms of stroke, such as severe headache, drowsiness, confusion, and dizziness. Emphasize the importance of regular follow-up visits.
❑ If aspirin has been prescribed to minimize the risk of embolic stroke, tell the patient to watch for GI bleeding related to ulcer formation. Make sure the patient realizes that he can’t substitute acetaminophen for aspirin.
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
More About Cerebrovascular accident
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Medical Books Excerpts
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- "Professional Guide to Diseases (Eighth Edition)" (2005)
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- Stroke
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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