7.3.1 Cerebrovascular Accident
A cerebrovascular accident（CVA），or stroke，is a syndrome characterized by the rapid onset（minutes to hours）of neurologic symptoms such as sensory abnormalities，aphasia，hemiparesis，or hemiplegia.
Subtypes of CVA include ischemic stroke and hemorrhagic stroke（Fig.7-5）.An ischemic stroke is typically caused by blockage of a blood vessel.A hemorrhagic stroke is caused either by intracerebral hemorrhage secondary to hypertension，cerebral amyloid angiopathy，or degenerative arterial disease；and the other is secondary to subarachnoid hemorrhages caused by rupture of an aneurysm.
Fig.7-5 Common Types of Stroke
Diagnosis is typically based on a physical exam and supported by medical imaging such as a CT or MRI scan.A CT scan can rule out bleeding，but may not necessarily rule out ischemia.Other tests such as an electrocardiogram（ECG）and blood tests are done to determine risk factors and rule out other possible causes.Prevention includes decreasing risk factors，surgery to open up the arteries to the brain in those with problematic carotid narrowing，and administration of warfarin in people with atrial fibrillation.
The successful management of acute ischemic stroke is currently based on two vascular recanalization strategies：anti-platelet agents and thrombolysis.Because most strokes are due to thromboembolic occlusion of an intracranial artery，restoration or improvement of perfusion to the ischemic area is the key therapeutic strategy.(https://www.daowen.com)
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Task 3 Define the meaning of each medical term given below.
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