My dr said my thoracic syrinx is congenital and idiopathic i have never had symptoms. is it likely to grow? it worries me. it ws found by accident.

It may get larger: Yes, the syrinx can get larger with time. If you follow up with doctor and keep them abreast of any changes in how you feel then, they will be able to determine whether or not it is growing and do the appropriate studies to check it out. Otherwise, don't worry, you were born with it....Just be aware of it....Don't be obsessed with it.