Hi and welcome to the Chiari forum.
Are u sure it was a sling? Or could it have been a patch? Many times the Dr places a dura patch and it can be from a cadaver, bovine, synthetic or they can use ur own pericardium (own skin) ...I had this done, but it was not a sling...ur Dr may have done something diff back then....I just know they do not do that now.
It is possible that u have scar tissue or have an issue with the "sling"
Do u have symptoms that have returned that u r asking, if so, what symptoms r they>?