What is a stroke?
A stroke, sometimes called a "brain attack," is an injury to the brain related to problems with blood flow. Stroke is the 5th leading cause of death and the number one cause of serious, long-term disability in the United States, with about 6.5 million stroke survivors alive today.
What causes a stroke?
There are two types of stroke: hemorrhagic and ischemic. A hemorrhagic stroke occurs when brain arteries rupture. An ischemic stroke occurs when blood supply to part of the brain is cut off.
An ischemic stroke occurs when the blood supply is cut off from part of the brain, often related to a clot or a plaque. When this happens, the blood-deprived brain tissue loses its supply of oxygen and nutrients. When brain tissue is deprived of blood for more than a few minutes, the brain tissue begins to die. Brief losses of neurological functions often occur before a full-blown stroke and are called transient ischemic attacks, or TIAs. A TIA occurs when blood flow to a certain part of the brain is cut off for a short period of time, usually 15 minutes or less. Although TIA is a painless episode, it is an important warning sign. TIA warning signs are similar to those of strokes, even though TIAs do not last. These include symptoms like loss of speech, vision problems, weakness of muscles, and severe headaches. Ischemic strokes tend to result from either clotting of an already narrowed vessel, much like in a typical heart attack, or from clots that form elsewhere and then lodge in the vessels that supply the brain.
The term hemorrhagic means flow (or torrent) of blood, referring to bleeding into or around the brain. Symptoms of this type of stroke are similar to those of an ischemic stroke. The major subtypes of hemorrhagic stroke are: subarachnoid, parenchymal, and intraventricular. They depend on where the bleeding is located. In hemorrhagic strokes, brain arteries rupture from high blood pressure, abnormal blood vessel walls, or from an aneurysm (an abnormal outpouching of a blood vessel). The rupture causes blood to flood the brain, creating pressure that leads to significant brain injury. A subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke where bleeding occurs in the subarachnoid space, a specific area between the layers surrounding the brain. This space also contains a clear fluid called cerebral spinal fluid. A common cause of subarachnoid hemorrhage is rupture of an aneurysm. Some other causes of subarachnoid hemorrhage include:
- Arteriovenous malformations (AVMs, or abnormal and snarled blood vessels)
- Dural fistulae or shunts (abnormal blood vessels of the dura)
- Vasculitides of the cerebrovasculature (conditions that cause inflamed blood vessels)
A parenchymal or intracerebral hemorrhage (ICH) involves the neurons and glial cells of the brain. An intraventricular hemorrhage (IVH) involves bleeding into the ventricles, fluid filled spaces in the brain where cerebral spinal fluid is made.
What are the signs and symptoms of a stroke?
Many warning signs indicate you may be suffering a possible stroke. Depending on the function of the part of the brain that is under attack, the person suffering the stroke suddenly may become paralyzed, blind or unable to speak. If you experience any of the major stroke warning signs listed below, call 911. It is important to get to a hospital immediately. The signs are:
- Sudden loss of speech
- Slurred speech
- Sudden loss of vision
- Blurry or double vision
- Sudden paralysis
- Sudden weakness
- Sudden dizziness
- Sudden severe headache, often with neck stiffness and vomiting
Remember that “time is brain.” The longer that brain cells go without fresh blood and oxygen makes the damage more likely to be permanent. The chances for survival and recovery improve when treatment begins within the first hours after a stroke has occurred.