Here or should I say 'there' is something I'd found which defines ATAXIA pretty well. Click on the blue here to get to 'there'?
http://neurotalk.psychcentral.com/thread102358.html
There might be things in the posts or 'stickies' above that post that could give to you the clue you need to get things [tests and treatments] done!

My heart is with you as it is a CHILD here that needs help! And, I'll bet that you are outta your mind with all sorts of thoughts. This is all going to make sense in the end? You don't think so now, but IT will! Learn LOTS, ask stupid and SMARTER questions and maybe, we can all help. But we gotta know more?
When did this all start?
Were there 'shots' or the like preceding it all?
Was there something for which antibiotics were used?
Anything, anything else!
We are NOT DOCTORS! But? We have all suffered in the medical 'food processer' in some ways or in many. We more than understand the 'I must be going crazy'! Thing as, we have all been there ourselves, either about us or our kids. We share so folks can avoid the pitfalls of those worst of scenarious! I do know and can attest that many here have helped save ME in some instances. I am sure these good people will try to help you too!
Come back and Tell us more? And know we aren't voyeurs or worse. Each person here has been where you are in a different way and can offer help in lots of different directions!
As for the ataxia? Tell your little lady that I too fall down more than I care to! AND I'm A grown-up! [Hummm, at least? Last I looked?]
Hugs and hope always - sometimes solutions are simple? Other times not-but, there are solutions out there. NO TREATMENT is not an answer - diagnosis IS!
- j