Hi and welcome to the Chiari forum.
I had a CINE MRI with and without contrast as it is helpful to see what is going on when it is lit up with the contrast. I also had the PFD surgery back in May of '09 and I am doing so much better as a result.
Head trauma can cause a Chiari like issue OR it can trigger Chiari to flare.....so knowing which is going on will be helpful. When was the trauma, sometimes it can correct itself. If you have true Chiari, since birth, it could be the trauma triggered the symptoms to flare. You may have had symptoms all your life but not aware since for you how you felt was "normal" for you...until they escalated.
There are many related conditions you should have ruled out, which in turn may help you figure out if indeed your Chiari is a true Chiari meaning you were born with it.
Please keep asking questions and we will try to answer them, if I missed one or didn't quite answer , ask again.
Know you are not alone.