oh boy! On the surface it sounds like he may have gone to doctors until he heard what he wanted to hear. I hope for his sake he just stays retired.
What he is saying is that the first doctor told him he was done, he was at a high increased risk of death or paralysis.
He was encouraged by friends and family to seek additional opinions, and when he did, every other doctor told him that he does in fact have the condition, but it doesn't mean he is at any increased risk at all. His odds of being injured or killed are the same as any other player.
Now, I don't want to pretend to be a doctor here, but what he's being told kind of makes sense. He was born with a condition that did not allow the disk in his C1-C2 to fully form. So he has a very reduced cushion between two critical vertebrae.
In all reality, if any of us takes a bone crushing hit in that spot, we're paralyzed or dead. There is no amount of "disk" between them to absorb the blow of a few thousand pounds of force.
To say he is at higher risk because his was under-formed stands contrary to reason. Again, I am no doctor, but I have serious back issues, and I know for fact those disks don't do a whole lote to absorb impact. They provide comfort from not having your bones grind together all day, but that are not there to absorb great impact, thickness be damned.