There are four general ways aneurysms are treated: (1) they can be clipped, (2) they can be coiled, (3) they can be treated with parent artery occlusion, or (4) they can be bypassed.
Clipping:
Cerebral aneurysms can be treated by placing a titanium clip to pinch-off the aneurysm.
Coiling:
Cerebral aneurysms can be treated with coiling, a minimally invasive treatment in which tiny platinum coils are placed within the aneurysm to block it off. The coils are inserted through a very narrow plastic tube (catheter) that is inserted in the patient's groin and navigated to the brain.
Parent Artery occlusion
The vessels that supply blood to the brain are connected with each other (Circle of Willis). If the bloodflow is in danger due to a certain disease in an artery, it is often possible to occlude the diseased vessel. This is called Parent Artery Occlusion.
The blood vessels comprising the Circle of Willis will then compensate for this intentional blockage with by supplying blood to the brain from another source. To test whether the occlusion of this vessel is possible, a small balloon will be temporary placed in the vessel. This balloon will be puffed up so that it will occlude the vessel. When the artery tolerates this, and the blood flow is proven sufficient, the balloon will then be removed and the artery permanently occluded. 
Bypass:
When permanent parent artery occlusion is not tolerated well, the surgeon can decide to make a bypass as a treatment option. Surgeons can decide to construct a bypass together with other treatments such as clipping, coiling, and parent artery occlusion.
A bypass procedure creates a “bridge” connecting the two strong parts of the artery together, leaving the aneurysm (or diseased weak part) in between. The “bridge” is usually constructed by using a blood vessel graft from another part of your body (usually the lower leg). This blood-vessel graft or “bridge” constitutes the bypass.
Conventional Bypass Technique
During the bypass surgery, the flow of blood in the diseased artery may need to be stopped for a short time. The risk of closing the diseased vessel even temporarily can result in loss of blood circulation to a section of the brain, thus reducing vital oxygen supplies. This reduction in oxygen supply is called a “stroke,” which can result in a loss of some brain function. A “stroke” can occur naturally, but can also result from the temporary blockage of an artery during surgery.
The ELANA Technique
If your doctor feels that it may be safer to avoid stopping the flow of blood in a diseased artery during surgery, he or she may decide to use the ELANA Technique. ELANA makes it possible to create a bypass in the diseased artery without having to stop the flow of blood. Use the following link to learn more about the ELANA Technique.