Like the AZ said, I'd want another opinion. And I'd want to follow up with more MRIs. Maybe in time that kink will straighten out.
I can't say - I'm not a dr - what is up with your son. But one thing I can say is right now it is as important what symptoms he has as what any scan or test shows. Please keep track of that. It can help his doc figure out what's going on.
Anything that happens within the brain, spine or nerves can produce symptoms. And for me, I worry more about how it affects me symptom wise than how scary it looks in the films.
Hope that helps.