Stroke is defined as an acute neurological deficit lasting more than 24 hours and caused by cerebrovascular aetiology. It is subdivided into ischaemic stroke (caused by vascular occlusion or stenosis) and haemorrhagic stroke (caused by vascular rupture, resulting in intra-parenchymal and/or subarachnoid haemorrhage). Ischaemic stroke accounts for about 85% of cases and haemorrhagic stroke about 15%. 
Regardless of the specific aetiology, ischaemic 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 ischaemic strokes are caused by cerebral sinus or cortical vein thrombosis. Risk factors strongly associated with ischaemic stroke include smoking,  diabetes,  atrial fibrillation,  comorbid cardiac conditions,  carotid artery stenosis,    and sickle cell disease. 
Cause of a minority of ischaemic strokes. Carotid revascularisation of high-grade asymptomatic, and moderate or high-grade symptomatic, carotid artery stenosis helps to prevent future stroke.
Cerebral ischaemia 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 ischaemic events. Evaluation and initiation of secondary prevention should occur rapidly.
Intra-cerebral haemorrhage is caused by vascular rupture with bleeding into the brain parenchyma. Three-quarters of haemorrhagic strokes are due to intra-cerebral haemorrhage, with the rest being due to subarachnoid haemorrhage. Strong risk factors include anticoagulation,   use of illicit sympathomimetic drugs,  and vascular malformations. 
Typically asymptomatic until ruptured, resulting in a subarachnoid haemorrhage. Screening with non-invasive neuroangiography is recommended for at-risk populations.
A medical emergency where there is bleeding into the subarachnoid space. The most common cause of non-traumatic subarachnoid haemorrhage is intra-cranial aneurysm. Strong risk factors include hypertension, smoking, family history, and autosomal dominant polycystic kidney disease. 
BMJ Publishing Group
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