I am not sure if this is something that progresses over time, or if what we are seeing on MRI now is what we will always see. That's one thing you could ask (if you want).
From what I have learned from my friend, it is something that is frequently missed and misdiagnosed, and it can absolutely change over time. She was just diagnosed this year when she was over 40, but she said looking back she has had symptoms her whole life. They have just gotten more severe recently for her, which lead to more testing and the diagnosis. They can be different from person to person (and day to day), and the symptoms and severity can change over time as well. Chiari can also cause symptoms outside of headaches. I know my friend and her one DD suffer from difficulty sleeping, arm weakness, eye pressure... Her oldest DD, who is now 15, was diagnosed when she was either 11 or 12 and had surgery at age 13. Things have progressed for her again where she may be facing another surgery. I know at one point she was having MRIs at least every six months, if not more frequently, to monitor how things were changing. However, each person is different. So where your DS is now may not change, or it may. Again, I am in no ways an expert, but if your DS has been diagnosed with Chiari, I would highly recommend working with a doctor who has expertise with Chiari to understand what your DS needs. I can get you names of doctors if you would like. I know both my friend's children have physical restrictions to prevent any sort of head injury -- no trampolines, no roller coasters, no sports with balls, no gymnastics, no horse-back riding, etc. After a long recovery, the oldest DD was feeling good after her first surgery, and she started running cross-country. They have now learned that was a mistake because all the bouncing that her body did progressed her symptoms to the point where she may need surgery again.
