Well, I don't know how many doctors he's
seen, but I can think of 2 things to keep in mind:
Doctors are people too, and they don't know EVERYthing... if they are talking about a risk of paralysis, they could very well just feel fine saying "no martial arts forever" just to be safe. Me and my brother have both had dentists tell us to get root canals, although we haven't and nothing ever happens... OK that is a little different, but think about that if a professional wants to be conservative about a root canal, of COURSE it is a good idea for a professional to be conservative about a potential spinal cord injury. They talk about THEIR field, like everyone else.. what about a doctor who does Aikido, his story might be different. Of course, there is I'm sure quite a bit of value in what his doctors have been saying.. it does sound risky to continue doing Aikido. BUT....
As I was saying about doctors potentially being ignorant about Aikido.... we all know Aikido can be very vigorous, but it never HAS to be. More vigorous just might be more fun sometimes, or more self-defense-like training sometimes... but I think a VERY CAREFUL person could still do Aikido in his situation... but yes I think a lot of changes should be made.. i.e. slow and careful for a very long time, forever maybe. "Polish the mirror" time..... I believe there is an article about that on this site... Anyway this might sound like I don't know what I'm talking about, but come on, "no martial arts forever" ???!!? What about Tai Chi??? That won't paralyze you!! Obviously "No martial arts" isn't quite right, so indeed maybe "modified Aikido" is possible.
Of course, if there is indeed a possiblity of physical recovery beyond what has been expected, as Ledyard Sensei suggested, that should be the first course of action......
There's my opinion..