Medical Health Encyclopedia

Hemorrhagic stroke

Some people with brain hemorrhage have abnormal connections between arteries and veins. Under normal circumstances, circulating blood travels through the arteries into the capillaries, where it provides nutrients and oxygen to the tissues. Once the blood has deposited the nutrients and oxygen, it is carried back to the heart from the capillaries via the veins.

In some people, however, a brain artery may connect directly to a vein, instead of going through the capillaries first. This is called an arterial-venous malformation (AVM). Since blood pressure in the arteries is much greater than in the veins, the veins may rupture, causing bleeding into the brain.

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.