Multiple sclerosis (MS) is a chronic neurodegenerative disease of the central nervous system. It often has an unpredictable disease course and can lead to a variety of disabling symptoms. Most people living with MS are first diagnosed with relapsing-remitting MS (RRMS). Over time, the RRMS may progress to secondary progressive MS (SPMS). A smaller number of people begin with primary progressive MS (PPMS), which is characterized by a steady worsening of symptoms from the start.
Some people living with MS eventually reach a point that their disease progression appears to stop. From there, they experience only mild symptoms without developing major disability. This mild disease course is sometimes called benign or burned-out MS, although controversy surrounds these terms and what they mean.
“Benign MS” (BMS) is a term used to describe mild MS that shows little or no change in disease progression after about 15 years. Doctors do not know why some people develop benign MS while others do not, although immune system changes are likely involved. Benign MS — sometimes called “inactive MS” — is reported in about 5 percent to 10 percent of people with MS.
Benign MS cannot be diagnosed when a person first develops the disease — or even several years later. There is also no way to predict whether someone with MS will ultimately have benign MS. Once a person goes approximately 15 years with little to no disease exacerbations, a doctor may classify their MS as benign. This means there is no evidence of worsening disability or lesions seen on MRI scans of the brain and spinal cord. Disease progression may still occur later on, however.
“Burned-out MS” describes situations when MS progression slows down significantly later in life. The terms “benign” and “burned-out” are often used interchangeably, and neither form has an official clinical definition.
There is controversy surrounding benign and burned-out MS. Some clinicians question whether these forms of MS exist, and there is no agreement about how to define these conditions. It is also unclear whether classifying a person’s MS as benign or burned-out positively impacts their doctor’s treatment plan.
Definitions of BMS vary considerably, as do estimates of how common the condition is. Some studies define benign MS as a lack of physical but not cognitive disability. Incidence rates of benign MS range from 6 percent to 64 percent of the total MS population. Large-scale studies show that nearly 40 percent of people living with RRMS do not transition to SPMS, nor do they develop significant disability.
Most definitions of BMS are based on disease duration and lack of physical disability. Typically, the Expanded Disability Status Scale (EDSS) is used to quantify the amount of disability. This scale is heavily focused on physical dysfunction and does not include cognitive impairment or mental health measures such as fatigue, anxiety, and depression. Defining benign MS based on the EDSS also does not recognize impaired social functioning, such as employment status, which is an important component of overall well-being.
Some studies show that more than half of people treated for RRMS and who were classified as having benign MS showed cognitive worsening. However, it is challenging to determine whether those cognitive deficits are due to an individual’s past MS flares or to normal age-related changes. More research is needed to better understand and define BMS.
In MS, the body’s immune system damages the myelin coating that covers nerves in the CNS. This damage creates the lesions that cause MS symptoms. Disease-modifying therapies (DMTs), including medications that block antibodies, suppress the immune system involved in these autoimmune responses. Although effective at treating MS, DMTs may cause undesirable side effects.
People with BMS often do not need aggressive treatment. Some people may want to stop DMTs once they reach a benign MS state, especially if they suffer from intolerable medication side effects. It is always important to speak with your doctor before stopping or changing a medication.
Disease-modifying therapies provide short-term benefits in people with active MS. These medications do so by reducing the severity of relapses and the likelihood of forming new lesions. However, continuing DMTs in those with benign MS is controversial. Some small studies suggest that stopping DMTs in older individuals does not correlate to more disease activity, compared to those who remain on DMTs. Thus, stopping DMTs may be safe in older people. Future studies are needed to determine whether discontinuing DMTs is safe in younger people.
Again, those considering stopping DMTs should discuss the specifics of their MS with their neurologist or other primary doctor before making any medication changes.
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