I, too, can't walk on my own, I use a rollator because I also have balance issues too. Did you get the GAD65 antibody test (although if it is negative, that does not mean you do not have SPS). I also ran the gamut of testing, etc. And the depression...well, I understand where you are coming from. I recently contacted a few people via e-mail that have SPS and it is nice to know that some of the more bizarre symptoms are shared by all of us. I am not a doctor, but I have read there are some good results with IVIg therapy in managing the disease (BUT it is VERY EXPENSIVE if your insurance won't cover it). The depression can be overwhelming, especially since the disease makes it hard for us to even go outside because the symptoms are exacerbated. I also go onto the www.ataxia.org board because they sometimes have good information about the walking issues. That may be helpful to you. As a some recent new SPS friends have pointed out to me, YOU ARE NOT ALONE.
Keep the faith and keep it moving!!
God Bless You!!