You may be surprised to know that there are unique types of multiple sclerosis. While they share some features, the science behind them, their course, and their symptoms can be quite different.
Relapsing-remitting MS is the most common type, affecting approximately 85 percent of those with MS. In this type of MS, a person will experience relapses of neurological dysfunction—these relapses are also called flares, bouts, attacks, or exacerbations. During a relapse, experts believe that there is an inflammatory attack on the myelin sheath—a covering that protects and insulates nerve fibers. The myelin sheath allows for proper, rapid communication among nerve cells, so when damaged, nerves cannot communicate properly and neurological symptoms arise.
The precise neurological symptom(s) that a person has depends on the location of the relapse within the brain or spinal cord. For example, if the optic nerve is the target of the relapse, a person may develop eye pain and blurry vision. If an area of the brainstem is affected, a person may experience tremor or problems with their balance.Some people regain all of their neurological function after a relapse, meaning their symptoms are reversible. Others gain only some (or none) of it back. It’s highly variable and symptoms can last days, even months. As the disease progresses, though, people tend to regain less and less function, and thus become more disabled.
The good news is that there are a number of medications approved for treating relapsing-remitting MS—13 to be exact. All of them have been shown in scientific studies to decrease both the number of relapses and number of new lesions on MRI. If you have been diagnosed with relapsing-remitting MS, it’s very likely that your neurologist will recommend starting one of these disease-modifying therapies right away.
Primary Progressive MS
Primary progressive MS is quite different from relapsing-remitting MS. For one, it’s found equally in both men and women—there is no gender discrepancy. It also typically affects those between the ages of 40 and 60, whereas relapsing-remitting MS affects a younger population, those in their 20s and 30s.
In addition, people with primary progressive MS almost always note difficulties with walking as their first symptom. For example, they may notice one or both legs dragging or becoming stiff or rigid. This is because, in primary-progressive MS, the disease significantly affects the spinal cord, so problems with walking, sex, and bladder and bowel function tend to dominate.
Also, experts believe that the science behind primary progressive MS is different from that of relapsing-remitting MS. In relapsing-remitting MS, there is an immune system attack on a nerve’s protective sheath (myelin). In primary progressive MS, there is a gradual deterioration of nerve fibers, favoring more of a degenerative process, rather than an inflammatory one.
This is why disease-modifying therapies do not seem to work (and are not yet FDA-approved) for primary progressive MS. Disease-modifying therapies target inflammation, which is not really occurring in primary progressive MS.
That being said, for some people, there may be an overlap between the two types, making the diagnosis tricky. This also explains why some neurologists will try a disease-modifying therapy for their patients, especially if the potential benefit outweighs any harms.
Secondary Progressive MS
Secondary progressive MS occurs when a person transitions from having relapses (relapsing-remitting MS) to a more gradual, progressive course (like primary progressive MS). Likewise, MRI images will show less contrast enhancing lesions (a sign of acute inflammation) and more atrophy or shrinking of nerve fibers (a sign of degeneration).
It’s interesting to note that the transition from relapsing-remitting to secondary progressive MS can occur quickly or very slowly, and this transition is not always clear cut. Sometimes a person will take on a more progressive MS course only to then develop a relapse with a new lesion on their MRI.
In terms of treatment, mitoxantrone is the only FDA-approved disease-modifying therapy to treat secondary progressive MS. Two of its major limiting side effects is its potential to cause heart damage and acute myeloid leukemia, a bone marrow cancer.
In 1996, progressive-relapsing MS was first described as a type of MS in which a person has a gradual worsening of their neurological function from the beginning, along with occasional relapses. But in 2013, the definition was revised—now those who were initially diagnosed with progressive-relapsing MS are considered primary-progressive “active” or “not active” (“active” meaning that a person is currently undergoing an MS relapse and “not active” meaning that a person is not currently experiencing relapses).Experts believe that people with progressive-relapsing MS become disabled quicker than those with primary progressive MS (someone who has no relapses). This is likely due to the fact that a person with progressive-relapses experiences a double whammy—relapses on top of a progressive decline in neurological function.
Clinically Isolated Syndrome (CIS)
CIS means that a person has experienced an episode that is characteristic of an MS relapse, but the person does not yet meet the criteria for a proper MS diagnosis. So it’s unclear whether that person will go on to develop MS. Some people with CIS will start a disease-modifying therapy, especially if their neurologist believes they are at a high risk for eventually developing MS.
A Word From Verywell
While it’s a good idea to understand the different types of MS, the big picture here is grasping the significant variability of MS as a disease. Even within the same type of MS, a person’s symptoms, disability, brain and spinal cord images, and how they feel and function each day is incredibly unique.This is why it’s important to focus on your own personal MS habits of coping and healing with your doctor and loved ones. So when an acquaintance (with good intentions) says that she has MS and is able to work full-time or garden every day, don’t feel bad. Your MS is different from her MS. Listen to your own body and be kind to yourself.