An Overview of Benign Multiple Sclerosis

Though benign multiple sclerosis (MS) might sound like an oxymoron, it's not—it's the mildest form of MS. There's no consensus on what exactly makes MS "benign," but it's always a diagnosis that's given retrospectively, usually 10 to 15 years after disease onset, once your healthcare provider can see how the disease has impacted you. This is because it's impossible to predict the twists and turns MS may take in each individual.

Definition

Benign MS is actually a somewhat controversial term since the definition isn't universally agreed upon and some experts think it's doesn't exist. In the first two decades or so, benign MS seems to manifest as mild relapsing-remitting multiple sclerosis (RRMS) in which few relapses occur. These relapses tend to produce sensory symptoms that go away and leave very little or no residual motor damage or disability.

The most commonly used definition of benign MS uses the Expanded Disability Status Scale (EDSS), which gauges your degree of disability. Benign MS is often diagnosed with a low EDSS score, usually 3 or below, which means you have some disability but you're still able to walk, 10 to 15 years (or more) after a diagnosis of MS.

Prevalence

It's impossible to know exactly how frequently benign MS occurs. One reason for this is that there are a number of people who have one clinically isolated syndrome event and never follow up, as well as those who never see a healthcare provider at all. Of these patients who have one event, around 15 percent never experience another.

Studies that estimate the prevalence of benign MS are all over the map too, mainly because there isn't a single agreed-upon definition and partly because they look at different populations.

For example, a 2019 study of MS patients in the United Kingdom looked at a population-based registry, where the researchers found 1,049 patients who had been diagnosed with MS for at least 15 years. Of these, 200 had a recent EDSS score of 4 or less. A sample of 60 of these patients was assessed in person to see who met the researchers' definition of truly benign MS, including:

• An EDSS score of less than 3
• Never received disease-modifying drugs
• No employment disruption
• No serious fatigue
• No symptoms of depression
• No cognitive impairment

Nine of the 60 patients fit the researchers' criteria for truly benign MS (15 percent). The researchers extrapolated this number to estimate that 30 of the 1,049 patients have truly benign MS, which comes out to 2.9 percent—far below the majority of other estimates. As a comparison, the National Institute of Neurological Disorders and Stroke (NINDS) says that benign MS occurs in 10 percent to 20 percent of MS patients.

Another example of the wide range of estimated prevalence in studies comes from a 2019 study published in Brain and Behavior, which looked at 125 patients in the United States with possibly benign MS. The researchers estimate that when going by the EDSS definition alone, benign MS affects around 23 percent of people with MS of 15 years or more. However, if cognitive impairment is included in the definition, this number falls to 16 percent.

Controversy

Overall, many neurologists and researchers prefer not to use the term "benign MS" because of the lack of an exact, accepted definition. There are a variety of debilitating symptoms of MS besides motor ability, and many of them are simply not factored into the EDSS definition. These less visible MS symptoms include:

• Fatigue
• Depression
• Anxiety
• Cognitive difficulties
• Pain

These symptoms can be just as disabling as motor ability—if not more so—in terms of affecting your quality of life and your ability to perform daily activities of living.

For instance, a 2012 study in Multiple Sclerosis found that after 10 years, 81 percent of people initially diagnosed with benign MS experienced a significant worsening of their cognitive function, fatigue, pain, or depression—symptoms of MS that are not evaluated in the EDSS.

In the same study, 74 percent of people with benign MS had a significant increase in the number of new or enlarging MS lesions on their magnetic resonance imaging (MRI) scans, without a change in their EDSS. This means that imaging of their central nervous system showed a progression of MS, even though their physical abilities (like walking) were not affected.

A progression of their MS would never have been known if they had not undergone MRIs.

Self-Reported Benign MS

In the aforementioned 2019 UK population study, when given a general definition of a benign condition—it has few or no adverse effects, no complications, and a good prognosis—39 of the 60 patients self-reported their MS as benign. The researchers found that in these patients, there was a significant association with lower EDSS scores, fewer symptoms of depression, less fatigue, and an overall lower impact of MS symptoms than in those who didn't self-report benign MS.

However, the actual status of self-reported benign MS was nowhere near meeting the researchers' criteria and only somewhat close to the EDSS definition. All of this illustrates not only the difference between how patients and healthcare providers define benign MS, but also the idea that a patient's perception of his or her disease may factor into how much MS symptoms impact his or her life.

In fact, the 2019 Brain and Behavior study authors proposed that benign MS should be at least partially defined by patients who are educated about MS and can observe and estimate the sort of impact it has on their lives. In that study, 75 percent of patients self-reported their MS as benign.

Predictors

Though there's never any way to know exactly how your MS will progress, even if your symptoms are mild in the beginning, research has found some commonalities that may indicate a benign pattern to the course of the disease.

A 2017 review of studies on benign MS found the following strong predictors for having benign MS and maintaining that status for another 10 years:

• An onset of relapsing-remitting MS (RRMS)
• Just one relapse in the first five years after diagnosis
• An EDSS of 2 or less five years after diagnosis or 3 or less 10 years after diagnosis

Treatment

Since it is not possible to predict at symptoms' onset which patients will have benign MS, most neurologists recommend a disease-modifying agent to their MS patients soon after the diagnosis.

Outlook

The outlook for benign MS isn't clear. Some people who are diagnosed with it never go on to have a more serious disease progression, while others do. Remember, just because you have mild symptoms when you're first diagnosed with MS doesn't mean that they'll stay that way. Keep in mind, too, that it takes at least 10 years, if not 15, to even get a diagnosis of benign MS in the first place.

A Word From Verywell

Regardless of the precise terminology, MS is a complex disease, and everyone's course and symptoms are unique. Even having a diagnosis of benign MS doesn't preclude you from having symptoms like fatigue, cognitive impairment, or depression. The individual way this disease presents itself only emphasizes the importance of having close follow-ups with your neurologist and remaining proactive in your MS health.