Hi and welcome to the Chiari forum.
We are not medical professionals here....so we can not tell you what your NL may say of know if you can work etc....
You indicate you have a syrinx that is different from a tarlov cyst.....so I am not sure that it spread as I feel it would have said the tarlov cyst grew. A syrinx develops when there is an obstruction to CSF flow, this could be due to your disk issue. It is possible they thought it was a tarlov cyst and now see it is a syrinx??? Not sure, only your Dr can explain that .
May I ask, do you feel you also have Chiari, is that why you posted in this forum? What other testing have you had?
"get that Note from the doc that referred me".