The changes are often difficult to recognize. But you may notice that relapses may not seem to fully go away.
Most people with relapsing-remitting MS -- about 80% -- eventually develop secondary progressive MS. The relapses and remissions that used to come and go change into a steady, gradual worsening of the disease. The shift typically begins 15 to 20 years after first being diagnosed with MS.
Because multiple sclerosis is such a complex and variable disease, the change to SPMS can be difficult to identify, even for health professionals. Doctors often wait at least six months before making a diagnosis of SPMS.
Symptoms of Secondary Progressive MS
Although relapsing-remitting MS can be unpredictable, the pattern of clear attacks followed by recovery is consistent. With SPMS, relapses tend to be less distinct. They may happen less often or not at all. When relapses do occur, recovery is not as complete. Disabilities linger.
Symptoms that may indicate you are progressing to SPMS include:
Diagnosis of SPMS can only be made by comparing symptoms over time. So it's important that you accurately tell your doctor about changes in your symptoms. Doctors use something called the Kurtzke disability scale to help measure disease progression.
Cause of Secondary Progressive MS
The reason people progress from relapse-remitting to secondary progressive MS is not clear. It does not seem related to an increased immune response.
One theory is that the disease progression may be an after-effect of nerve injury that occurred early in the disease. But more research is needed to understand the shifting disease process.
Treatment of Secondary Progressive MS
Treating secondary progressive MS is often more difficult than treating relapsing-remitting MS.
The main class of drugs for MS -- called disease modifying drugs (DMDs) -- is used to reduce the severity and frequency of relapses. For people with SPMS who still have relapses, DMDs, such as interferon, can still help. But, for those with disease progression without relapses, the drugs are not generally considered useful.