A stroke happens when part of the brain is damaged because of either the blockage of a blood vessel or the rupture of a blood vessel in the brain.

A stroke can happen in one of 2 ways: a blood vessel in the brain can either get blocked (cutting off blood flow; called ischemic stroke) or start bleeding (called hemorrhagic stroke). Strokes caused by blockage are much more common than strokes caused by bleeding. Things that increase the risk of having a stroke include high blood pressure, high cholesterol, diabetes, smoking, an abnormal heart rhythm calledatrial fibrillation, and lack of physical activity. Therefore, maintaining a healthy lifestyle and taking medications for any of these other medical conditions will lower your risk of stroke.

When the brain does not get enough blood flow, many different signs and symptoms can occur. The amount and type of symptoms depend on what part of the brain is involved.

Some of the common signs of stroke include

• Asymmetry in the face or a droop on one side of the face

• Weakness on one side of the body (such as an arm, leg, or both)

• Numbness or unusual sensations on one side of the body

• Trouble speaking (speech is slurred; cannot repeat a simple phrase)

Time is the most important factor if you think you are having a stroke. The faster you can get to a hospital, the better your chances of recovery. Therefore, you should call the paramedics right away if you have any of the above warning signs—do not “wait it out” to see if the symptoms get better on their own.

The reason that time is very important is that for some strokes, a medication that dissolves blood clots can be given through the bloodstream as treatment. This medication only works during the first few hours after a stroke. After that it is no longer effective and can even cause harmful side effects. Therefore, it is very important, when possible, to record the exact time that you or someone around you first noticed symptoms and the time that you were last well without symptoms.

In the April 23/30, 2014, issue of JAMA, an article discusses a study that was done to try to improve the time delay in giving clot-dissolving medications for stroke. The idea was to give the clot-dissolving medication in the ambulance on the way to the hospital instead of after arriving at the hospital, and this study showed some promising early results.