I have had 2 spinal cord tumors and 2 syrnix with the 1st tumor. They were both removed surgically at Johns Hopkins by Dr. George Jallo. He'll look at MRI's for nothing if you're looking for another opinion.
In my case, once the tumor was removed the syrnix went away on their own without a shunt.
As for the sports question I can't answer that. But someone on the forum for spinalcordtumor.org may know.