When a vessel in the brain forms a weak spot, it may fill with blood and bulge like a balloon. This bulging spot is a brain aneurysm. Depending on its size and where the aneurysm forms, these weak spots can be dangerous. They may break open (rupture) and allow blood to leak into the brain. Neurosurgeons can clip brain aneurysms to ensure they don't rupture. A small metal clip (or clips) is placed over the neck of the aneurysm to prevent blood entering it. Without a blood supply, the aneurysm is no longer at risk of breaking open and shrinks over time. Clipping for cerebral aneurysm is an effective procedure to permanently close it and prevent the risk of bleeding.