Tethered cord

Has anyone been told they did not have a tethered cord only to have a second opinion and find out they actually do? I am possibly facing this scenario.

I'm facing this with my 8 year old son. He had decompression 8-2011. He had a very large syrinx. We've been struggling with bowel, bladder incontinence. Pain/tingling in legs, feet, and arms. Also, he's having more headaches. After 1 1/2 years of back and forth with neurosurgeon and neurologist, our wonderful neurologist suggested a second opinion with another neurosurgeon. She sent us to Vanderbilt. We had a consult appt and ns there told us my son has symptoms of tc . We are in the process of waiting of a MRI to see if he has tethered cord or lower syrinx. I'm a nervous wreck because I don't want to think of that surgery. I would've thought the tc or lower syrinx couldve been seen on previous scans?