Lecture 3: Central Nervous System - Cerebrovascular Accident (CVA) PDF

CHAPTER THREE Central nervous system In this chapter, you’ll learn: Cerebrovascular accident (CVA) - Classification, risk factor, causes, types, symptoms, prevention, diagnosis and Treatment of stroke.  Cerebrovascular accident (CVA) Stroke...

CHAPTER THREE Central nervous system In this chapter, you’ll learn: Cerebrovascular accident (CVA) - Classification, risk factor, causes, types, symptoms, prevention, diagnosis and Treatment of stroke.  Cerebrovascular accident (CVA) Stroke Previously known as cerebrovascular accident, stroke is a sudden impairment of cerebral circulation in one or more of the blood vessels supplying the brain. It interrupts or diminishes oxygen supply, causing serious damage or necrosis in brain tissues. Although it mostly affects older adults, it can strike people of any age. Black populations have a higher risk than other population groups. Classification of stroke Stroke is classified according to how it progresses: Transient ischemic attack (TIA), the least severe type, is caused by a temporary interruption of blood flow, usually in the carotid and vertebrobasilar arteries. Progressive stroke, begins with a slight neurologic deficit and worsens in a day or two. Completed stroke, the most severe type, causes maximum neurologic deficits at the onset. Risk factor of stroke Factors that increase the risk of stroke include: History of TIA. (Recognizing and treating TIAs can reduce the risk of a major stroke. TIAs produce stroke-like symptoms but most have no lasting effects) Atherosclerosis. Hypertension. (It's the biggest cause of strokes) Arrhythmias. (This condition includes defective heart valves as well as atrial fibrillation, or irregular heartbeat, which causes a quarter of all strokes among the very elderly) Electrocardiogram changes. Rheumatic heart disease. Diabetes mellitus (People who have it often have high blood pressure and are more likely to be overweight. Both raise the chance of a stroke. Diabetes damages your blood vessels, which makes a stroke more likely)  Gout Cardiac enlargement High serum triglyceride levels Lack of exercise. (the chances of a stroke may go up if you're overweight) Hormonal contraceptive use. Drug abuse (Drugs including cocaine and heroin are associated with an increased risk of stroke). Smoking (Nicotine makes the blood pressure go up. Cigarette smoke causes a fatty buildup in the main neck artery. It also thickens the blood and makes it more likely to clot) Family history of cerebrovascular disease Sickle cell disease. (Sickle cell disease, a genetic condition that can narrow arteries and interrupt blood flow). Causes of stroke Major causes of stroke include: -Thrombosis. -Embolism. -Hemorrhage. Thrombosis: ü Thrombosis is the most common cause of stroke in middle- aged and elderly people. ü It usually results from an obstruction in the extracerebral vessels, but sometimes it’s intracerebral. ü The risk increases with obesity, smoking, hormonal contraceptive use, and surgery. Embolism: ü The second most common cause of stroke, embolism is a blood vessel occlusion caused by a fragmented clot, a tumor, fat, bacteria, or air. ü It can occur at any age, especially in patients with a history of rheumatic heart disease and other cardiac arrhythmias. ü It also occurs after open-heart surgery. ü Embolism usually develops rapidly—in 10 to 20 seconds—and without warning. Hemorrhage: ü Hemorrhage, the third most common cause of stroke, may also occur suddenly at any age. ü It arises from chronic hypertension or aneurysms, which cause a sudden rupture of a cerebral artery. ü Increasing cocaine use by younger people has also increased the number of hemorrhagic strokes because of the severe hypertension caused by this drug. Brain aneurysm Types of strokes There are 2 main types of strokes: ischaemic and haemorrhagic. Ischaemic Strokes: o An ischaemic stroke occurs when a thrombus or embolus impairs cerebral blood flow. o One of the most common causes of ischaemic strokes are those that are associated with atherosclerosis, in which the lumen of arteries are narrowed, leading to a thrombus forming. o This thrombus then occludes the vessel which, when occurring in the brain, results in the cerebral ischaemia – otherwise known as a thrombotic stroke. o An embolic stroke can also occur when a thrombus breaks away and becomes an embolus. o This embolus can then be carried to the brain from another part of the body and occlude a cerebral blood vessel causing cerebral ischaemia. Haemorrhagic Strokes: o A haemorrhagic stroke occurs when there is a rupture in a cerebral blood vessel that causes bleeding in the brain. o The main cause of haemorrhagic strokes is hypertension, but they can also be brought on by anatomical defects such as aneurysms, arteriovenous malformations (AVMs) or degenerative changes occurring in arterial walls. o An aneurysm occurs when there is a weakened part of a blood vessel wall that balloons out. o This section of the blood vessel wall can continue to weaken until it eventual ruptures and bleeds into the brain. o AVMs (arteriovenous malformations) occur when there is a cluster or a tangle of abnormally formed blood vessels. o These blood vessels bypass normal brain tissue and divert the blood from the arteries to the veins. When these AVMs rupture they then cause bleeding.  General Symptoms of stork  Weakness in the arm or leg or both on the same side.  Weakness in the muscles of the face.  Difficulty speaking.  Coordination problems.  Dizziness.  Vision problems.  Sudden headache.  Loss of consciousness. Prevention Many stroke prevention strategies are the same as strategies to prevent heart disease. In general, healthy lifestyle recommendations include: Controlling high blood pressure (hypertension). Lowering the amount of cholesterol and saturated fat in diet. Quitting tobacco use. Controlling diabetes. Maintaining a healthy weight. Eating a diet rich in fruits and vegetables. Exercising regularly. Treating obstructive sleep apnea (OSA). Avoiding illegal drugs. Anti-platelet drugs. Anticoagulants. Diagnosis of stroke These tests are used to diagnose stroke: Cerebral angiography details disruption or displacement of the cerebral circulation by occlusion or hemorrhage. It’s the test of choice for examining the entire cerebral circulation. Digital subtraction angiography evaluates the patency of the cerebral vessels and identifies their position in the head and neck. It also detects and evaluates lesions and vascular abnormalities.  CT scan detects structural abnormalities, edema, and lesions, such as nonhemorrhagic infarction and aneurysms.  Cerebral angiogram A cerebral angiogram showing a carotid aneurysm associated with stroke. CT scan of brain tissue damaged by stroke  PET scan provides data on cerebral metabolism and cerebral blood flow changes, especially in ischemic stroke. Single-photon emission tomography identifies cerebral blood flow and helps diagnose cerebral infarction. MRI and magnetic resonance angiography evaluate the lesion’s location and size. MRI doesn’t distinguish hemorrhage, tumor, or infarction as well as a CT scan, but it provides superior images of the cerebellum and brain stem. Transcranial Doppler studies evaluate the velocity of blood flow through major intracranial vessels, which can indicate the vessels’ diameter.  Cerebral blood flow studies measure blood flow to the brain and help detect abnormalities. Ophthalmoscopy may show signs of hypertension and atherosclerotic changes in the retinal arteries. EEG may detect reduced electrical activity in an area of cortical infarction and is especially useful when CT scan results are inconclusive. It can also differentiate seizure activity from stroke. Treating stroke Medical treatment for stroke commonly includes physical rehabilitation, dietary and drug regimens to help decrease risk factors, and measures to help the patient adapt to specific deficits, such as speech impairment and paralysis. Drug therapy Drugs commonly used for stroke therapy include: Thrombolytic therapy such as recombinant tissue plasminogen activator given within the first 3 hours of an ischemic stroke to restore circulation to the affected brain tissue and limit the extent of brain injury Anti-con-vulsants such as phenytoin to treat or prevent seizures Stool softeners such as docusate to avoid straining, which increases intracranial pressure Corticosteroids such as dexamethasone to minimize cerebral edema Anticoagulants, such as heparin, warfarin, and ticlopidine, to reduce the risk of thrombotic stroke. Analgesics such as codeine to relieve headache that may follow hemorrhagic stroke. Surgery Depending on the stroke’s cause and extent, the patient may also undergo surgery.