Friend, he cannot just leave this alone, you'll lose him if he does. Sounds like he doesn't want to do anything out of fear and that can and just might cost him his life. This could be something very easy to treat RIGHT NOW, the longer he goes the worse it will get, nothing bad just goes away. I have a Chiari 1 which is a brain herniation
caused from an accident and for the first few months I just ignored it and went right on working and living life like nothing was wrong. When the headaches
got so bad I was pulling out my hair I knew I had to do something and trust my Lord, and my doctors, now I will see my daughter graduate, go to college, marry, have babies! I am so thankful. You sound like a wonderful friend, keep nudging him, you may even talk to your own doctor about his condition and see if he / she can give you some advice. Don't give up on him!! Bless you and best of luck.