My good friend's daughter just had the corrective surgery for it 2 years ago.
(She had the kind where parts of her skull were ground down to make more room for her brain, and then a skin "sling" was made that holds her brain upward even more. The "sling" also protects her brain from smacking into her skull during trauma.)
She's doing FANTASTIC. No killer headaches at ALL for the past 2 years, and only a couple normal ones. From an aesthetic point of view, the scar is under her hair (only had to shave a few inches.) Quick recovery time.
And yes. A car accident could *absolutely* make it worse. Much much worse. It wouldn't necessarily make it worse, but it very easily could.
I've been told I may have a mild form of it (for now, could get worse). Since it's a huge trigger for migraines, it'll probably become a much more common diagnosis in the coming years.
R