When a knot of malformed or otherwise abnormal blood vessels occurs it’s known as arteriovenous malformation. Such knots—believed to result when an artery connects to a vein without the necessary capillaries—are likely to bleed, and therefore when they occur in the brain they can be very serious and potentially life threatening.

Because they are formed in the pre-natal stage, arteriovenous malformations typically accompany abnormal development of brain tissues. Occurring in less than one percent of the population, the size and location of arteriovenous malformations can vary and the signs and symptoms of the condition can present at any age.

The danger of arteriovenous malformations is that they can rupture or burst from pressure, which likely will cause damage to the surrounding tissues and thereby reduce the flow of blood to the brain. In terms of signs and symptoms of the condition, they are dependent on the size and location of the anomaly (in some cases there may be no signs or symptoms at all). But when markers of the problem are present, sufferers will most likely have seizures (a result of a disturbance of the electrical activity in the brain); headaches from increased blood flow; and signs that mimic a stroke, including paralysis or weakness on one side of the body, sensation, hearing, vision and balance problems and a loss of memory or drastic change in behavior.

Various forms of angiography—in which a dye is injected into the blood in conjunction with imaging technologies that detect the size and location of the arteriovenous malformation—are used in diagnosing the condition, and treatment can take several forms. Often, a liquid/glue substance is injected into the arteriovenous malformation to block it off, and sometime the abnormality is bombarded with x-rays in order to reduce its size. And in surgical situations the arteriovenous malformation is removed completely.

Treatments for arteriovenous malformations range from embolization to radiation therapy to surgical removal, that latter of which requires a craniotomy (a procedure used to access the tissues and vital portions of the brain by the removal of a section of the skull known as a “bone flap”).

While under general anesthesia, a patient’s head is secured to prevent movement during the craniotomy. A surgeon begins by making an incision and pushes away skin and muscle structures. One or possibly more small holes are drilled into the bone of the skull, and a saw is used to cut between the holes and remove a section known as the bone flap. The outermost membrane covering the brain—the dura—is now visible and accessible, and the surgeon cuts through this layer to reach the brain itself.

Once the blood vessel with the arteriovenous malformation is found, the surgeon isolates it from the surrounding brain tissue and removes the malformation in one piece. The dura is closed and the bone flap is returned to its original position and secured in place by plates and screws, and the skin is restored and sutured or stapled shut.

Post-craniotomy, a patient will typically be taken to an intensive care unit for monitoring and recovery from anesthesia, and they may be placed on a ventilator to assist with breathing. Once the patient is awake, physicians will check for normal breathing ability and that body movements are intact, and that there are no physical or mental complications as result of the surgery. A hospital stay lasts a few days, and patients will most likely receive some form of rehabilitation to help them return to normal daily activities.