Multiple sclerosis (MS) is a chronic autoimmune, neurodegenerative disease that attacks the central nervous system (CNS). These attacks lead to the breakdown of myelin, the protective cover that shields the nerve fibers in the CNS.
Scar tissue forms at the sites of these breakdowns, which may prevent the CNS from communicating with the rest of the body. When that happens, you may lose function over time.
MS symptoms can come and go, sometimes without treatment. There is often a lot of variability among different people with the same diagnosis and even in the same person over time.
MS is an unpredictable disease. If you receive a diagnosis of MS, it's normal to wonder what your disease course might be like.
Clinically Isolated Syndrome
The first time you experience any symptoms of MS, like blurred vision, muscle weakness, or a feeling of "pins and needles," your doctor will likely describe the episode as an example of clinically isolated syndrome (CIS).
The next step will be an MRI scan to see if there are any signs of scarring in your brain or spinal cord. Your doctor may also discuss starting you on medication, even though it's too early to make an official diagnosis of MS.
That's because an MS diagnosis typically requires at least two attacks of neurological symptoms at least one month apart, as well as MRI evidence of CNS scarring.
Not all people with CIS go on to develop MS. If the MRI taken during CIS shows brain lesions typically seen in MS, you are to develop MS over time. If your MRI does not show scarring even though you have neurological symptoms, you are less likely to develop MS.
Relapsing-Remitting MS
Relapsing-remitting MS is the most common type of MS, with about 85% of people with the disease initially receiving this diagnosis. When you have periods of time with neurological symptoms, with onset gradually over hours to days and that lasts more than 24 hours in the absence of fever or infection, that's known as a relapse. Remission, refers to when the symptoms resolve.
People usually feel well during remissions, which can last for weeks, months, or even years, noted Lindsay Ross, MD, of the Cleveland Clinic's Mellen Center for Multiple Sclerosis Treatment and Research. "There may be some residual symptoms even during remissions, but there is an overall pattern of relapsing and remitting."
Just as the disease course of MS varies between people, symptoms can change in intensity from day to day, or even hour to hour. But just because symptoms may flare, that doesn't mean a new relapse has begun. "A symptom must be new and persist for more than 24 hours for us to consider that a relapse," explained Sammita Satyanarayan, MD, of the Icahn School of Medicine at Mount Sinai in New York City.
Secondary Progressive MS
Over time, some people with relapsing-remitting MS will transition into secondary progressive MS, which means that an individual is experiencing gradual worsening of function over time separate from relapses. The disease progresses more consistently than with relapsing-remitting disease, and the familiar cycle of relapse and remission often resolves into more steady disease progression.
"If a patient's disease starts with an acute attack, or relapse, we will start by labeling them with relapsing-remitting disease. But then if they begin to lose abilities over time, that's when we would say they have secondary progressive disease," Ross said. "You cannot technically move from relapsing-remitting to primary progressive, but you can move to secondary progressive disease."
Primary Progressive MS
People who do not experience relapses have primary progressive MS. Their symptoms worsen steadily over time. About 10% of people with MS receive this diagnosis.
"It's easy for patients to imagine that their loss of function will keep going at the same rate and that they will end up in a wheelchair in a set period of time, but it's often not like that," Satyanarayan said. "Instead, there might be periods where symptoms stabilize -- sometimes for a long time -- before worsening again."
Radiologically Isolated Syndrome
Radiologically isolated syndrome (RIS) is currently not considered a disease course of MS, although that may change in the future. The term describes a person whose MRI shows lesions on the brain or spinal cord typical of those seen in MS, even though there are no past or current symptoms of MS.
RIS is often diagnosed when a person receives an MRI for another condition, perhaps because they have bad headaches or were in an automobile crash. There are currently no treatment guidelines for RIS.
In 2020, a global study that followed people with RIS for 10 years found that about half went on to develop MS.
Looking Toward the Future
Many people who have MS ask their doctor what they can expect from the disease in the future. Unfortunately, there is no easy answer to that question.
"Nowadays, we are pretty good at looking at large groups of people and predicting what the group's average level of disability might be like in 5 or 10 years," said Kevin Patel, MD, of UCLA Health in Los Angeles. "But it's very hard to predict an individual person's prognosis over time."
Some factors do seem to increase the chance of poor individual outcomes, Ross noted. "If someone has more damage in their spinal cord than in their brain, that's harder to compensate for functionally. Or someone who has a lot of relapses very quickly soon after diagnosis has a lot of inflammation, which can lead to worse outcomes, but it's not universal."
Read Part 1 of this series: For Your Patients: What to Expect After a Multiple Sclerosis Diagnosis
"Medical Journeys" is a set of clinical resources reviewed by doctors, meant for physicians and other healthcare professionals as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.