Hello and welcome,
Sometimes the sx will come back due to scar tissue causing problems or if you returned to the same habits and activites that may have caused TOS to occur.

Have you had any TOS PT or posture therapies?
Or have you been trying any self care to help stop the return of symptoms?

here are the links to our dr list & some PTs also our useful links for TOS
http://neurotalk.psychcentral.com/showthread.php?t=135
http://neurotalk.psychcentral.com/showthread.php?t=84