This reminds me of Jack Nicholson in Con Air somewhere around the beginning. Him and his wife(from what I remember) were walking out of a bar, were jumped, and since Nicholson was in the Military and hit the guy in such a way that the nose bone shot straight up the guys brain and killed him. Forgive me if I'm wrong. Anyways, I believe it COULD be possible. For what I think, it really depends how the fight it going. Plus Anatomy you gotta think of. The way the bone structure is built it seems like it could be really hard to do. Somebody could develope enough force if they had the right amount of momentum.