Stroke is defined as an acute neurologic deficit lasting more than 24 hours and caused by cerebrovascular etiology. It is subdivided into ischemic stroke (caused by vascular occlusion or stenosis) and hemorrhagic stroke (caused by vascular rupture, resulting in intraparenchymal and/or subarachnoid hemorrhage). Ischemic stroke accounts for 87% of all stroke cases, hemorrhagic stroke for 10%, and subarachnoid hemorrhage for 3%. 
Regardless of the specific etiology, ischemic stroke occurs when blood supply in a cerebral vascular territory is critically reduced due to occlusion or critical stenosis of a cerebral artery. A minority of ischemic strokes are caused by cerebral sinus or cortical vein thrombosis. Risk factors strongly associated with ischemic stroke include older age, family history, hypertension,  smoking,  diabetes,  atrial fibrillation,  comorbid cardiac conditions,  carotid artery stenosis,    sickle cell disease,  and dyslipidemia. 
Cause of a minority of ischemic strokes. Strong risk factors include older age, smoking, and history of cardiovascular disease.  Carotid revascularization of high-grade asymptomatic, and moderate or high-grade symptomatic, carotid artery stenosis helps to prevent future stroke.
Cerebral ischemia should be suspected when a patient presents with typical symptoms of rapidly resolving unilateral weakness or numbness, but also with less classic symptoms such as unilateral vision loss, transient aphasia, or vertigo. TIAs have considerable risk of early recurrent cerebral ischemic events. Strong risk factors include atrial fibrillation, valvular disease, congestive heart failure, hypertension, diabetes,  carotid stenosis,  cigarette smoking,  alcohol abuse,  and older age. Evaluation and initiation of secondary prevention should occur rapidly.
Intracerebral hemorrhage is caused by vascular rupture with bleeding into the brain parenchyma. Three-quarters of hemorrhagic strokes are due to intracerebral hemorrhage, with the rest being due to subarachnoid hemorrhage. Strong risk factors include family history, older age,  hemophilia, cerebral amyloid angiopathy, hypertension,  anticoagulation,   use of illicit sympathomimetic drugs,  vascular malformations,  and Moyamoya syndrome. 
Typically asymptomatic until ruptured, resulting in a subarachnoid hemorrhage. Screening with noninvasive neuroangiography is recommended for at-risk populations. Strong risk factors include smoking, moderate-high level alcohol consumption,  family history, previous subarachnoid hemorrhage, and heritable connective tissue disease. 
A medical emergency where there is bleeding into the subarachnoid space. The most common cause of nontraumatic subarachnoid hemorrhage is intracranial aneurysm. Strong risk factors include hypertension, smoking, family history, and autosomal dominant polycystic kidney disease. 
BMJ Publishing Group
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