Hi and welcome to the Chiari forum.
I am so sorry and as CW mentioned above wish there was more we can do, other then offer a shoulder and listen.
What we suggest for older individuals is to get to a true Chiari specialist...u will need a pediatric Chiari specialist...and to get to one u may have to travel.
We do have a list of Drs that the members here have been to, treated by and liked....however the list is not a referral. nor an endorsement for the names listed...it is just a starting point for u to research to find the right Dr for u and ur child.
Make sure they do test him for sleep apnea....this is many times overlooked and is very very important for everyone but especially children and infants.
Do u know which came first? The hydro?....as that can cause the cerebral tonsils to herniate.....
I know this is a very scary and frustrating time, the best thing u can do, is what u r, reaching out and educating urself on these conditions so u can make an informed decision for ur son.
Know u r not alone, and we will support u and help get answers to ur questions the best we can.....I know we have had a few children represented on this forum by parents, but I do feel urs may be the youngest that I remember.....that said there are more informed Drs in treating these conditions today, it is a matter of locating and traveling to them.
Check ur INS to see what type of coverage u have....and get copies of ALL testing done on ur DS....MRI's on disk and reports...blood labs etc....it will make getting a 2nd or 3rd opinion faster and easier.
http://www.medhelp.org/health_pages/list?cid=186