A stroke is a medical condition in which poor blood flow to the brain causes cell death.[5] There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding.[5] Both cause parts of the brain to stop functioning properly.[5] Signs and symptoms of a stroke may include an inability to move or feel on one side of the body, problems understanding or speaking, dizziness, or loss of vision to one side.[2][3] Signs and symptoms often appear soon after the stroke has occurred.[3] If symptoms last less than one or two hours, the stroke is a transient ischemic attack (TIA), also called a mini-stroke.[3] A hemorrhagic stroke may also be associated with a severe headache.[3] The symptoms of a stroke can be permanent.[5] Long-term complications may include pneumonia and loss of bladder control.[3]

Other namesCerebrovascular accident (CVA), cerebrovascular insult (CVI), brain attack
CT scan of the brain showing a prior right-sided ischemic stroke from blockage of an artery. Changes on a CT may not be visible early on.[1]
SpecialtyNeurology, stroke medicine
SymptomsInability to move or feel on one side of the body, problems understanding or speaking, dizziness, loss of vision to one side[2][3]
ComplicationsPersistent vegetative state[4]
CausesIschemic (blockage) and hemorrhagic (bleeding)[5]
Risk factorsHigh blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, previous TIA, end-stage kidney disease, atrial fibrillation[2][6][7]
Diagnostic methodBased on symptoms with medical imaging typically used to rule out bleeding[8][9]
Differential diagnosisLow blood sugar[8]
TreatmentBased on the type[2]
PrognosisAverage life expectancy 1 year[2]
Frequency42.4 million (2015)[10]
Deaths6.3 million (2015)[11]

The main risk factor for stroke is high blood pressure.[6] Other risk factors include tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, a previous TIA, end-stage kidney disease, and atrial fibrillation.[2][6][7] An ischemic stroke is typically caused by blockage of a blood vessel, though there are also less common causes.[12][13][14] A hemorrhagic stroke is caused by either bleeding directly into the brain or into the space between the brain's membranes.[12][15] Bleeding may occur due to a ruptured brain aneurysm.[12] Diagnosis is typically based on a physical exam and supported by medical imaging such as a CT scan or MRI scan.[8] A CT scan can rule out bleeding, but may not necessarily rule out ischemia, which early on typically does not show up on a CT scan.[9] Other tests such as an electrocardiogram (ECG) and blood tests are done to determine risk factors and rule out other possible causes.[8] Low blood sugar may cause similar symptoms.[8]

Prevention includes decreasing risk factors, surgery to open up the arteries to the brain in those with problematic carotid narrowing, and warfarin in people with atrial fibrillation.[2] Aspirin or statins may be recommended by physicians for prevention.[2] A stroke or TIA often requires emergency care.[5] An ischemic stroke, if detected within three to four and half hours, may be treatable with a medication that can break down the clot.[2] Some hemorrhagic strokes benefit from surgery.[2] Treatment to attempt recovery of lost function is called stroke rehabilitation, and ideally takes place in a stroke unit; however, these are not available in much of the world.[2]

In 2013, approximately 6.9 million people had an ischemic stroke and 3.4 million people had a hemorrhagic stroke.[16] In 2015, there were about 42.4 million people who had previously had a stroke and were still alive.[10] Between 1990 and 2010 the number of strokes which occurred each year decreased by approximately 10% in the developed world and increased by 10% in the developing world.[17] In 2015, stroke was the second most frequent cause of death after coronary artery disease, accounting for 6.3 million deaths (11% of the total).[11] About 3.0 million deaths resulted from ischemic stroke while 3.3 million deaths resulted from hemorrhagic stroke.[11] About half of people who have had a stroke live less than one year.[2] Overall, two thirds of strokes occurred in those over 65 years old.[17]