When it comes to multiple sclerosis, you can’t really look at any one patient’s experience as representative of the condition; that’s because symptoms of MS can vary widely from patient to patient. Depending on where lesions form on the central nervous system, MS may affect different parts of the body for each patient, like the legs, fingers, or vision.
Doctors categorize multiple sclerosis into four main types, based on the progression of the disease. This diagnosis does matter since it can affect treatment. “There are different classifications for MS, and that is really based on the patient’s symptoms and what the patient tells us,” says Michelle Fabian, MD, a neurologist at The Mount Sinai Hospital.
There are four main courses MS can take: progressive-relapsing MS, secondary progressive MS, primary progressive MS, and relapsing-remitting MS.
What Is Relapsing-Remitting MS?
The most common type of MS is relapsing-remitting, affecting 85 percent of MS patients at diagnosis. The key characteristic of this type is relapses, or flare-ups, of MS symptoms, followed by periods of lessened or no symptoms.
Doctors define relapses as a new attack, localized somewhere on the body, that causes symptoms that last longer than 24 hours, according to Dr. Fabian. After the attack, the patient makes a partial or full recovery and may not experience new symptoms for weeks, months, or even years.
Because the patient may not fully recover between relapses, each relapse may exacerbate the condition and increase disability over time. Treating relapsing-remitting MS focuses on preventing relapses, which will keep the condition from progressing. Learn more about relapsing-remitting MS here.
What Is Primary Progressive MS?
Primary progressive MS affects about 15 percent of MS patients at diagnosis, according to the National MS Society. Instead of relapses that come and go, patients with primary progressive MS see a slow and steady progression of their symptoms over time.
“Instead of a new symptom that comes on over days to weeks, it’s a slow thing that happens over months to years,” says Dr. Fabian. “It’s more of a gradual symptom, and then it doesn’t typically go away. It might kind of plateau—flatten out—but it doesn’t go away.”
Learn more about the characteristics of primary progressive MS here.
What Is Secondary Progressive MS?
A patient with relapsing-remitting MS may be diagnosed with secondary progressive MS if, over time, relapses stop occurring and the disease switches to a more gradual worsening of symptoms.
“[Patients with SPMS] have a history of those episodes of [central nervous system] inflammation,” says Dr. Fabian, “but those stop. What happens after that is they develop a progressive course.”
What Is Progressive-Relapsing MS?
This disease course is the rarest of the four, according to Dr. Fabian. Progressive-relapsing MS begins as a progressive course, gradually becoming more severe, and then the patient experiences a relapse—a flare-up of symptoms on a new part of the body.
In addition to the four main types of MS, doctors may also diagnose a patient with clinically isolated syndrome. “We have patients with one symptom of MS, and their MRI looks like a mild form of MS,” says Dr. Fabian. “That would be CIS.” If the patient has another relapse—as many do—doctors would then consider that relapsing-remitting MS. Here’s more information about clinically isolated syndrome.
Thanks to recent treatment advances for MS, most patients with relapsing-remitting MS won’t develop secondary progressive MS, unlike in the past. New medications have become more effective at preventing relapses, thus helping to stave off the progression of the disease.