Ok so some places to get started.
Firstly I recommend you read some books by Glenn Doman. In your case what to do about your brain injured child would be a great place to start. Then his physically superb book will give you even more ideas. Hre is the website link for information but most of the time the books are available from the library or amazon.
http://www.gentlerevolution.com/mm5/merchant.mvcAfter that to ease your future communication problems have you considered teaching some sign language? There are many threads on baby signing time on this forum, it could alleviate some frustration as you work on speach development. Little reader does wonders for enhancing vocabulary understanding and hearing all the words articulated separately and clearly often helps children develop speech.
Talking alot to children as you go about your every day life is another valuable technique. Chatter constantly about what you are doing. Don't just pick up the toys, talk about the toys as you pick them up.
I think it would be a good idea to work on both speech and physical skills now. Rather than just focus on communication. You child has some catching up to do in a physical sense. It's best to get started on that now, the more practice kids get the better they are.
Keep reading everything on the forum. You have much to learn that will help your child succeed. Don't be discouraged by the lack of medical information, time and time again children here have proven the doctors wrong.
I have just given you some ideas to start. If you would like some specific advise from others with children of different chromosome patterns please start a new post with your questions. Many here are retry willing to help!
You are in the right place