Cat head trauma

My gorgeous Persian kitten of 7 weeks got a little smack on the bum for being naughty and then about a minute later he lost all control of bodily fluids and proceeded to convulse and bleed profusely out of the nose. I called the after hours vet and he said it was head trauma and after extensive research there's no doubt that that is the problem. Unfortunately I live in an  area where the equipment required is not available and it would cost thousands to get him flown to get treatment. Money that I just don't have lying around. After the first 36 hrs he started to recover quite speedily but after another 36 hrs his declined quite rapidly but not comatose. Its horrible to see his sister trying to play with him poor guy is the most active kitten iv ever had.. I guess my question lies in what possibly could have caused the head trauma and what's the likelyhood that he will fully recover ..