Hemorrhagic stroke

Another important brain disease that can cause bleeding is cancer. This is especially true for cancers that spread to the brain from distant organs, such as the breast, skin, and thyroid.

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About 20% of strokes are hemorrhagic -- but the other 80% are caused by the opposite problem: too little blood reaching an area of the brain, which is usually due to a clot that has blocked a blood vessel. This is called "ischemic stroke." This type of stroke can sometimes lead to a brain hemorrhage because the affected brain tissue softens and this can lead to breaking down of small blood vessels.

In addition, brain hemorrhage can occur when people have problems forming blood clots. Clots, which are the body's way of stopping any bleeding, are formed by proteins called coagulation factors and by sticky blood cells called platelets. Whenever the coagulation factors or platelets do not work well or are insufficient in quantity, people may develop a tendency to bleed excessively.

Some medications (often used, ironically, to prevent ischemic stroke) prevent clot formation. These work by blocking the production of clotting factors (such as the blood thinner warfarin) or interfering with the function of platelets (such as aspirin). The most common side effects of such medications is bleeding, which may occasionally affect the brain. Controlling bleeding to avoid stroke is a very fine balancing act.

Illicit drugs, such as cocaine, can also cause hemorrhagic stroke.