Matt gets beat to within an inch of his life, and winds up with severe head trauma and neurological damage. He stutters and gets angry because his words won't come out right, his hands shake so badly at times that he can't even take a drink of water without spilling it on himself. Foggy's there with him every step of the way because no matter what, he'll never leave Matt's side.

Up to the author whether or not the damage is permanent, but oceans of angst and comfort would be nice.