Head CT > Stroke > Ischemic stroke


Ischemic stroke

Ischemic strokes are caused by thrombosis, embolism of thrombosis, hypoperfusion and lacunar infarctions. A thrombotic stroke occurs when a blood clot forms in situ within a cerebral artery and blocks or reduces the flow of blood through the artery. This may be due to an underlying stenosis, rupture of an atherosclerotic plaque, hemorrhage within the wall of the blood vessel, or an underlying hypercoagulable state. This may be preceded by a transient ischemic attack and often occurs at night or in the morning when blood pressure is low. Thrombotic ischemic strokes account for 53% of all strokes.
An embolic stroke occurs when a detached clot flows into and blocks a cerebral artery. The detached clot often originates from the heart or from the walls of large vessels such as the carotid arteries. Atrial fibrillation is also a common cause. Embolic strokes account for 30% of all strokes.
A lacunar infarction occurs when the walls of small arteries thicken and cause the occlusion of the artery. These typically involve the small perforating vessels of the brain and result in lesions that are less than 1.5 cm in size.
Hypoperfusion infarctions occur under two circumstances. Global anoxia may occur from cardiac or respiratory failure and presents an ischemic challenge to the brain. Tissue downstream from a severe proximal stenosis of a cerebral artery may undergo a localized hypoperfusion infarction. Lacunar and hypoperfusion strokes, account for the remaining 1% of strokes of the ischemic type.

 



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