Hi and welcome to the Chiari forum.
First let me say, WOW...this is the longest I have heard of someone being post op for chiari PFD surgery...and no symptoms till now?...WOW again!!
This is great to hear....but, yes it is possible for symptoms to return...as she could have fallen...been on a bumpy car ride or even a MVA that could re-trigger the symptoms...as well as scar tissue...or bulging disks, they can cut off CSF flow too and cause many of the same symptoms as chiari.
I am not sure about the studies of surgery as children and now facing symptoms again as an adult....
May I ask do u know who her NS was?...and what type of surgery she had...there r several types...I know they used to do a bony decompression which is not as invasive as the PFD where they cut the dura...I have heard those that had this type..the bony...after a time would require the full PFD as the symptoms would return.Just never heard it would take this long, so if that is the case...she did great!!!
i have also had the decompression surgery as well 12 yrs ago and had a shunt placement as well at the age of 19. i am now 32 yrs and am just now experiencing some tightness and soreness in my neck but i havent had any other problems since. I have also been wondering the same thing tho.very good question...