PPMS is characterized by worsening neurologic function (accumulation of disability) from the onset of symptoms, without early relapses
or remissions. PPMS can be further characterized at different points in time as either active
(with an occasional relapse and/or evidence of new MRI activity) or not active
, as well as with progression
(evidence of disease worsening on an objective measure of change over time, with or without relapse or new MRI activity) or without progression
. Approximately 15 percent of people with MS are diagnosed with PPMS.
This graphic shows the kinds of disease activity that can occur in PPMS; however each person's experience with PPMS will be unique. PPMS can have brief periods when the disease is stable, with or without a relapse or new MRI activity, as well as periods when increasing disability occurs with or without new relapses or lesions on MRI.
Why are modifiers used to characterize PPMS?
Disease activity and progression should be evaluated at least yearly by neurologic examination and MRI. Being able to characterize the course of your disease course at different points in time helps you and your MS care provider have important conversations about your treatment options and prognosis. For example:
- If you have PPMS that is active, with new MRI activity or relapses, your conversation with your MS care provider could be about starting treatment with a disease-modifying therapy to reduce the risk of a relapse, as well as rehabilitation to help improve function and mobility.
- If you have PPMS that is stable without activity or progression, the conversation with your MS care provider should include the role of rehabilitation to help you maintain function, as well as other symptom management strategies that you may need.
- If you have PPMS that is not active (no new MRI activity or relapses) but is progressing with increasing accumulation of disability, the conversation with your MS provider needs to focus on the rehabilitation strategies that can help you maintain function and keep you safe and independently mobile.
How does PPMS differ from the other disease courses?
Although there is a lot of variability among people with PPMS, we know that as a group, they differ in several ways from people with relapsing forms of MS:
- Relapsing forms of MS (including relapsing-remitting MS, and secondary progressive in those individuals who continue to experience relapses) are defined by inflammatory attacks on myelin. PPMS involves much less inflammation of the type seen in relapsing MS. As a result, people with PPMS tend to have fewer brain lesions (also called plaques) than people with relapsing MS and the lesions tend to contain fewer inflammatory cells. People with PPMS also tend to have more lesions in the spinal cord than in the brain. Together, these differences make PPMS more difficult to diagnose and treat than relapsing forms of MS.
- In the relapsing forms, women are affected two to three times as often as men; in PPMS, the numbers of women and men are approximately equal.
- The average age of onset is approximately 10 years later in PPMS than in relapsing MS.
- People with PPMS tend to experience more problems with walking and more difficulty remaining in the workforce.
- In general, people with PPMS may also require more assistance with their everyday activities.