Brain aneurysms are weaknesses in the walls of the blood vessels of the brain, usually occurring at a point where a blood vessel branches. This weakness causes a bulging in the wall of the blood vessel. This bulge can take two general shapes. The first is called a "saccular" brain aneurysm and is a formation of a sac or pouch on one side of the blood vessel wall. The second type is called a "fusiform" brain aneurysm and is an outward bulging of the blood vessel wall in all directions.

Along with occurring within the brain itself, an aneurysm can occur within the major head and neck vessels leading to the brain, called the carotid arteries with the same devastating results. The Carotid arteries are the vessels in your neck forward of the large neck muscle on the side of your neck which can be felt pulsing. The carotid arteries are extremely prone to vascular disease which can weaken their structure leading to aneurysms.

Brain aneurysms can cause problems in several different ways. They may rupture and cause bleeding into the fluid spaces surrounding the brain or into the brain itself. This "hemorrhage" usually causes a severe headache, which is often described by the patient as "the worst of my life."

In addition, brain aneurysms may cause problems not related to bleeding. As an aneurysm grows, it may compress adjacent areas of the brain or specific nerves (such as the optic nerve, the nerve that transmit signals from the eye to the brain). Depending upon the location of the aneurysm, this mechanical pressure (mass effect) can result in a variety of symptoms including, but not limited to, abnormal sensations, blindness, seizures or paralysis. Additionally, some aneurysms contain blood clots that may dislodge and be carried by blood flow further into the brain, blocking smaller arteries, which can lead to a stroke.

An alternative to open surgery is the minimally invasive procedure known as endovascular embolization. With this technique, a tiny incision is made in the upper portion of the thigh, where a catheter (small tube) is placed into the large artery of the leg, and with x-ray guidance is advanced through blood vessels until it reaches the aneurysm site. The aneurysm is then "packed" with tiny thread-like coils that are passed through the catheter into the aneurysm. The coils and the body's reaction to them effectively seal off the aneurysm.

In contrast to conventional open surgery, this technique allows the aneurysm to be treated from the inside of the vessel, thus the name "endovascular" surgery. Endovascular embolization can be used to treat aneurysms in many locations and has been shown to be particularly useful in treating aneurysms that are very difficult or impossible to reach by conventional neurosurgical techniques.

Learn about brain aneurysm symptoms