I gotta give you credit... you just got out of brain surgery and the only thing you're worried about is your bowling game! Either you're hard-core, or they forgot to take out the part that is making you insane!
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Jokes aside, I hope all goes well and you have a quick recovery. As for the physical aspect, I dunno... I guess the best advice I could give there would be to stay on your feet as much as possible. Keep the legs strong. You could also get a racquet ball and squeeze on it to keep the hand strength up. Push ups to keep the upper body in shape (depending on how much you work out - if you're already hitting the gym during the week, I wouldn't bother with my suggestions). Other than that, I think the rest will come back after you throw a few sets.
As for the brain, well you're asking the wrong guy. My mental game has always been my weakness. lol But I guess you could try reading - there are a couple of books people recommend here quite often (I don't remember them, but they're targeted to the mental aspect of bowling). I should read them, but I haven't.
Best of luck to you, both on the lanes and off!
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9~Internet Tough Guy
Cyberspace Sheep Lover