I am also truly sorry for your loss, but you really do need the doctor who was treating his PN to answer this question, as you don't mention the actual cause of the accident as to if any other vehilces, road conditions, or anything else that may have initiated the accident.
Many years ago my uncle got a lend of his friends motor bike, road conditions were good and he was riding along safely but some idiot drunk stepped out from the medium strip right in front of him, he never had the time to do anything else but slam on the brakes, he was thrown off his bike and hit an old metal postal box and died soon after, the drunk survived, if he would have been driven a car the result would have been the opposite, so there's no wonder why i hate motor cycles, you have no protection around you like a car has and thats not saying your safe in a car either.