well from what Germ says its more of the brain swelling instead of chiari
which i assume for my lawsuit would be better than chiari
Germ seemed to indicate a chiari is congenital and that is the way I was reading it in that link you sent.
Since it seems the chiari can go undiagnosed since there are so many symptoms they could/would argue that you were born that way but it was never diagnosed and had nothing to do with the accident.