Secondary Progressive MS vs Relapsing-Remitting MS

One of the most common questions I am asked by patients is whether they are in the relapsing-remitting phase of MS or in the progressive phase of the illness. Lets again review what these terms mean. About 85% of patients start the illness with relapsing-remitting disease. This means that patients develop a neurological symptom, usually over the course of hours to days, that then spontaneously improves over the course of weeks to months. The improvement from relapses is usually quite good, though this is not always the case. Patients may then go months to years before they have another relapse, and there is no development of disability in between relapse.

The Secondary Progressive Phase

After a period of time, usually 10-30 years, patients will then enter what is called the secondary progressive phase of the illness. Patients who are diagnosed with MS at a younger age tend to remain in the relapsing-remitting phase longer compared to those who are diagnosed at a later age.  In the secondary progressive phase, relapses are very rare events.  However, patients may accumulate disability quite gradually from year to year.

Often times, it is quite clear when patients are in the relapsing-remitting or the secondary-progressive phase of the illness, but there is no formal transition between the two stages. In this way, it can be compared to asking “when does someone become old?”  My grandmother who recently turned 100 is old by any definition. But I certainly cannot tell you at what age this happened. 

The Importance in Determining the Stages of MS

Nevertheless, it is important to determine the stage of a patient’s MS to the best of our abilities. The treatments are only effective in the relapsing-remitting phase of the illness and have not been shown to be of benefit once someone has reached the progressive phase. One of the challenges faced by doctors and patients alike is to be bold enough to stop using medications for MS in patients who are clearly in the progressive phase of the illness and for whom relapses are no longer a feature of the disease.

Finally, it should be mentioned that the divisions of MS into relapsing-remitting and secondary progressive phases says nothing about the severity of the disease. There are patients with patients with mild progressive disease, and there are patients with severe relapsing disease.  So in this sense, one stage of the illness is not “better” than another.