A stroke is a sudden blockage of blood to the brain or bleeding in the brain that causes brain cells to die.
What causes a stroke?
The brain muscle needs a steady supply of oxygen-rich blood in order to function properly. If the flow of blood is interrupted by a blockage or by sudden bleeding in the brain, brain cells will begin to die.
There are two main kinds of stroke: ischemic and hemorrhagic.
Ischemic strokes are the most common. They occur when there is a blockage to an artery that supplies blood to the brain. There are two types of ischemic stroke: thrombotic and embolic. In thrombotic stroke, a blood clot (thrombus) forms in an artery that supplies blood to the brain.
In an embolic stroke, a blood clot or other substance (plaque, fatty material) travels through the bloodstream to an artery in the brain. (A blood clot or piece of plaque that travels through the bloodstream is known as an embolus). About half of all strokes in the United States are a result of carotid artery disease, which causes plaque to build up inside and narrow the carotid arteries.
A transient ischemic attack (TIA) is similar to an ischemic stroke in cause and symptoms, but it usually lasts one or two hours and does not cause permanent brain damage. TIAs can be a warning sign of a stroke and require immediate medical attention.
Hemorrhagic strokes occur when an artery in the brain leaks blood or bursts, damaging brain cells. There are two types of hemorrhagic stroke: intracerebral and subarachnoid. In an intracerebral hemorrhage, a blood vessel inside the brain leaks blood or ruptures. In a subarachnoid hemorrhage, a blood vessel on the surface of the brain leaks blood or ruptures. This causes bleeding between the inner and middle layers of the membranes that cover the brain. High blood pressure and aneurysms are common causes of hemorrhagic strokes.
Symptoms of a stroke
The symptoms of a stroke can vary from person to person and may develop quickly or over a period of several hours or even days. The type of symptoms experienced will vary depending on the type of stroke and the area of the brain damaged.
Common symptoms of a stroke include:
- Paralysis or numbness of the face, arms or legs, especially on one side of the body
- Trouble speaking or understanding speech
- Trouble seeing in one or both eyes
- Difficulty breathing
- Dizziness or loss of balance or coordination
- Loss of consciousness
- Sudden and severe headache
How are strokes diagnosed?
Your doctor can diagnose a stroke by evaluating your medical history, your symptoms, and the results from several tests, including:
- Blood tests
- Brain computed tomography (CT)
- Carotid angiography
- Carotid ultrasound
- Computed tomography (CT) arteriogram
- Electrocardiogram (EKG)
- Magnetic Resonance Arteriogram (MRA)
- Magnetic Resonance Imaging (MRI)
What are the options for treating a stroke?
Though both are medical emergencies, treatment options for a stroke depend on whether it is ischemic or hemorrhagic.
Treatments for ischemic stroke aim to break up blood clots in the arteries through one of the following:
- Medication, including tissue plasminogen activator (tape), antiplatelet medicines or blood thinners
- Medical procedures, including a carotid endarterectomy, carotid percutaneous intervention, or intra-arterial thrombolysis, which open blocked carotid arteries
Hemorrhagic strokes are treated by finding and stopping the cause of bleeding in the brain. Surgery may be needed to stop bleeding and repair damage in the brain, depending on what is causing the bleeding.
Surgical treatments for strokes caused by an aneurysm include:
- Aneurysm clipping
- Coil embolization
Treatments for hemorrhagic strokes caused by a tangle of arteries and veins that have ruptured include:
- Surgery to remove the tangle
- Injecting a substance into the tangle that blocks blood flow
- Radiation to shrink the blood vessels in the tangle