“Dandy Don” Meredith dies of brain hemorrhage

In a healthy, functioning brain, neurons do not come into direct contact with blood. The vital oxygen and nutrients the neurons need from the blood come to the neurons across the thin walls of the cerebral capillaries. The glia (nervous system cells that support and protect neurons) form a blood-brain barrier, an elaborate meshwork that surrounds blood vessels and capillaries and regulates which elements of the blood can pass through to the neurons.

When an artery in the brain bursts, blood spews out into the surrounding tissue and upsets not only the blood supply but the delicate chemical balance neurons require to function. This is called a hemorrhagic stroke. Such strokes account for approximately 20 percent of all strokes.

Hemorrhage can occur in several ways. One common cause is a bleeding aneurysm, a weak or thin spot on an artery wall. Over time, these weak spots stretch or balloon out under high arterial pressure. The thin walls of these ballooning aneurysms can rupture and spill blood into the space surrounding brain cells.

Hemorrhage also occurs when arterial walls break open. Plaque-encrusted artery walls eventually lose their elasticity and become brittle and thin, prone to cracking. Hypertension, or high blood pressure, increases the risk that a brittle artery wall will give way and release blood into the surrounding brain tissue.

A person with an arteriovenous malformation (AVM) also has an increased risk of hemorrhagic stroke. AVMs are a tangle of defective blood vessels and capillaries within the brain that have thin walls and can therefore rupture.

Bleeding from ruptured brain arteries can either go into the substance of the brain or into the various spaces surrounding the brain. Intracerebral hemorrhage occurs when a vessel within the brain leaks blood into the brain itself. Subarachnoid hemorrhage is bleeding under the meninges, or outer membranes, of the brain into the thin fluid-filled space that surrounds the brain.

Symptoms of a Stroke