Ideopathic vestibular syndrome in dogs--experiences?

Our dog went down with this a week ago Thursday, and the vet says he has the worst case she has seen. He seems to be making small progress daily, but he is still somewhat wobbly and unable to walk—he can’t tell his back legs what to do yet.
My research tells me that dogs recover from this, but the vet can’t say whether he will recover to the point that he has the use of his back legs again. I’ve heard of lots of dogs with less severe cases making a full recovery, but I am wondering if anyone has any experience with dogs that have been severely affected and what their recovery was like.
Thanks!