Sorry to hear of your PPMS diagnosis. Though there are no FDA-approved therapies for this form of MS, some patients are trying Solumedrol infusions, methotrexate therapy (this is a pill), some are experimenting with Tysabri infusions and Novantrone infusions, and one of my friends with PPMS is trying daily Copaxone injections. You must tell your doctors that you want to do more than symptom management. At the very least, they should let you know about clinical trials in which you might participate.
My other thought is that you might consider getting another opinion on your dx. If you have any doubts about your dx, if there has been an inflammatory phase and relapses in your recent past, then perhaps there is a chance that the drug therapies which treat RRMS might be beneficial to you right now. If you haven't already, ask your diagnosing doctor lots of questions about how they arrived at this dx.
If you are interested in experimental therapies, you can do some online research to find out more by visiting the Multiple Sclerosis Foundation, Multiple Sclerosis Association of America, Multiple Sclerosis Society, Cleveland Clinic, Mayo Clinic, The National Institute of Neurological Disorders and Stroke (NINDS), The National Institutes of Health (NIH), and visit other MS forums such as medhelp and healthcentral to read about what other PPMS patients are doing to manage their disease.
It's up to you to push for more treatment options. Please keep us updated on your progress and the treatments you might undergo. And take good care of yourself.
Kim