Clipping is a surgery performed to treat an aneurysm — a balloon-like bulge of an artery wall. As an aneurysm grows it can become so thin that it leaks or ruptures, releasing blood into the spaces around the brain. A neurosurgeon opens the skull (craniotomy) and places a tiny clip across the neck of the aneurysm to stop or prevent it from bleeding. The goal of surgical clipping is to isolate an aneurysm from the normal circulation without blocking off any small perforating arteries nearby.