Stroke Support Group

A stroke, also known as cerebrovascular accident (CVA), is an acute neurologic injury whereby the blood supply to a part of the brain is interrupted, either by a clot in the artery or if the artery bursts. The result is that the part of the brain perfused by that artery no longer can receive oxygen carried by the blood and it dies (becomes necrotic) with cessation of function from that part of the brain. In addition to tissue death, hemorrhages also cause damage from physical impingement of blood on the brain tissue. Stroke is a medical emergency and can cause permanent neurologic damage or even death if not promptly diagnosed and treated. It is the third leading cause of death and adult disability in the US and industrialized European nations.

Risk factors include advanced age, hypertension (high blood pressure), diabetes mellitus, high cholesterol, and cigarette smoking. Cigarette smoking is the most important modifiable risk factor of stroke.

Strokes can be classified into two major categories: ischemic and hemorrhagic. Ischemia can be due to thrombosis, embolism, or systemic hypoperfusion. Hemorrhage can be due to intracerebral hemorrhage or subarachnoid hemorrhage. ~80% of strokes are due to ischemia.

Ischemic stroke

In ischemic stroke, which occurs in approximately 85-90% of strokes, a blood vessel becomes occluded and the blood supply to part of the brain is totally or partially blocked. Ischemic stroke is commonly divided into thrombotic stroke, embolic stroke, systemic hypoperfusion (Watershed stroke), or venous thrombosis.

Hemorrhagic stroke

A hemorrhagic stroke, or cerebral hemorrhage, is a form of stroke that occurs when a blood vessel in the brain ruptures or bleeds. Like ischemic strokes, hemorrhagic strokes interrupt the brain's blood supply because the bleeding vessel can no longer carry the blood to its target tissue. In addition, blood irritates brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, it can cause increased intracranial pressure which physically impinges on brain tissue and restricts blood flow into the brain. In this respect, hemorrhagic strokes are more dangerous than their more common counterpart, ischemic strokes. There are two types of hemorrhagic stroke: intracerebral hemorrhage, and subarachnoid hemorrhage.

As ischemic stroke is due to a thrombus (blood clot) occluding a cerebral artery, a patient is given antiplatelet medication (aspirin, clopidogrel, dipyridamole), or anticoagulant medication (warfarin), dependent on the cause, when this type of stroke has been found. Hemorrhagic stroke must be ruled out with medical imaging, since this therapy would be harmful to patients with that type of stroke.

In increasing numbers of primary stroke centers, thrombolysis ("clot busting") is used to dissolve the clot and unblock the artery. However, there is a time constraint: the more time that goes by, the more brain that has irreversibly died. There is also a small risk of making the patient worse by causing bleeding. When used within the first 3 hours, thrombolysis improves the outcome in 1 of every 3.1 patients and worsens the outcome in 1 in every 32 patients. The routine use of thrombolysis is not approved beyond 3 hours. As an easily administered therapy that can be given at any hospital with a CAT scanner, thrombolysis is available at most hospitals in the US, but not where no institutional commitment to stroke care has occurred.

Another intervention for acute ischemic stroke is removal of the offending thrombus directly. This is accomplished by inserting a catheter into the femoral artery, directing it up into the cerebral circulation, and deploying a corkscrew-like device to ensnare the clot, which is then withdrawn from the body. In August 2004, the FDA cleared one such device, called the Merci Retriever.[4]