At its most basic, secondary-progressive multiple sclerosis (SPMS) is a worsening form of MS that follows relapsing remitting multiple sclerosis (RRMS) in some people. SPMS occurs only in people who already have RRMS. The progression to secondary progressive MS is due to gradually worsening nerve damage. Without treatment, there’s a high likelihood RRMS will transition to SPMS. The change to SPMS typically happens about 15 to 20 years after the initial diagnosis.
When Walking Gets Harder
“The most common presenting symptom of SPMS is progressive difficulty walking,” says Joshua Katz, M.D., co-director of the Elliot Lewis Center, an MS care program in Wellesley, MA. “People start having more trouble walking distances, climbing stairs, and maintaining balance.”
Progression is typically slow and tends to take years, he says. At a certain point, some people may require a cane and, perhaps, later a walker; occasionally, SPMS will progress to the point that a wheelchair is necessary for getting around.
The Unpredictability of MS Progression
MS is an extremely variable disease that can be very mild or very severe; moreover, it can stop progressing at any time or start progressing again, says Fred Lublin, M.D., director of the Corinne Goldsmith Dickinson Center for Multiple Sclerosis at Mount Sinai Medical Center in New York City. “Unlike some degenerative neurological disorders, MS is very unpredictable and not guaranteed to worsen rapidly or at all.”
Some people see their MS stabilize and stay that way. Others will progress, though that number is shrinking since disease-modifying therapies (DMTs) became available. “The conversion to SPMS is not a foregone conclusion,” says Kathy Costello, C.R.N.P., associate vice president of healthcare access for the National Multiple Sclerosis Society (NMSS) in Baltimore.
“The good news is that thanks to disease-modifying therapies, symptom management, and frequent monitoring, your MS may never turn into SPMS," Costello says. "It’s possible, but you may never get there.”
Common Symptoms of SPMS
Symptoms of SPMS are unpredictable, vary from person to person, and can change over time. In relapsing remitting MS, symptoms usually occur in episodes, while in SPMS, symptoms worsen gradually over time, generally in the absence of a defined relapse.
In addition to difficulty walking and balance issues, symptoms of progression might include:
- Spasticity (tight muscles)
- Numbness and tingling
- Blurred vision
- Bladder problems
In those who go from RRMS to SPMS, it’s impossible to pinpoint exactly when one turns into the next. “It’s a transition that happens over time,” Costello says. In fact, it can take several years for your doctor to know for sure that you have progressed to SPMS, says Dr. Lublin. “The transition from one form of MS to the next is quite subtle.”
“With RRMS,” says Costello, “people have periods of time with new symptoms—numbness, weakness, vision changes—and then, over weeks to months, the symptoms improve, often with complete or partial recovery. Following a relapse, there’s a quiescent period, when you don’t have new or worsening symptoms. This remission may be followed at some point by another relapse.”
If you develop SPMS, you may still have relapses—although they generally occur less frequently than in RRMS. When a relapse happens, it’s called active SPMS, which is more likely to respond to DMTs than non-active SPMS. “The disease-modifying treatments that we have now may stall or limit the activity of the disease so you don’t ever experience a progression,” says Costello.
With SPMS, you may experience a gradual worsening of symptoms you had earlier, despite the fact that you’re no longer having inflammatory relapses. To make it even trickier for doctors to diagnose SPMS, some MS symptom exacerbations are so mild that you may not have realized they were an indication of progressive MS. You might write off a brief episode as a sign of fatigue or having a mild virus. In fact, that short, symptomatic episode could indicate you’ve passed through the relapsing-remitting phase of MS without being formally diagnosed with SPMS. If your symptoms worsen or remain after your last relapse, check in with your doctor.
Who Is at Risk for SPMS and Why?
Nearly 1 million people in the United States have MS, according to NMSS estimates. As is the case with most autoimmune disorders, about three times as many women are affected by MS as men, and the disorder seems to be more common in colder areas that are farther from the equator, where there may be less sunlight and, consequently, your body may produce less vitamin D.
Wherever they live, people of Northern European descent seem to run the highest risk of developing the disease, while Native Americans of North and South America, along with Asian Americans, have relatively low rates of MS. While women are more likely to have MS than men in general, men and women have the same risk of transitioning to SPMS, says Dr. Katz.
“It is thought that early and highly effective treatment may prevent people from getting SPMS, but this isn’t known for sure,” he says. “But it is clear that early treatment has an enormous impact on reducing later disability, whether or not one develops SPMS.” If there were no DMTs, about 50% of people with RRMS would progress to SPMS in 10 years or so. And about 90% would develop SPMS by 25 years after initial diagnosis. But thanks to newer treatments, it’s less likely.
“People often ask when they will become progressive,” Dr. Katz says. “It’s difficult to answer because it is very individual. But taking a disease-modifying therapy, managing symptoms, and maintaining a healthy life are all strategies to delay progression.”