Multiple sclerosis is a disease of the central nervous system. There are traditionally four forms of the disease that include relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), primary progressive MS (PPMS), and progressive relapsing MS (PRMS). A 2014 update to the description of the subtypes of MS added clinically isolated syndrome (CIS) to the list and removed PRMS. An unofficial subtype of multiple sclerosis is benign MS.
What is benign MS?
Although there is no universally agreed upon definition of benign MS (BMS), the term is typically used to describe a disease course where patients experience little disease progression and minimal accumulation of disability decades after developing the disease. Benign MS is a retrospective diagnosis that can only be made 10 years or more after disease onset.
Your neurologist may look back on how MS has affected you and determine that your version of MS has been “benign” or fairly mild. Disability in MS is measured by the Expanded Disability Status Scale (EDSS) that is scored from 0 (no disability) to 10 (death). An EDSS 2.0 score represents mild disability in one functional system, such as decreased sensation in all four limbs, and EDSS 3.0 represents mild disability in several functional systems or moderate disability in one system while the patient is still able to walk unassisted.
How common is benign MS?
Variation in the criterion used to describe BMS leads to a wide range of prevalence estimates between 20 and 33 percent among patients registered in the New York State MS Consortium (NYSMSC) database that includes more than 7,000 patients diagnosed with clinically definite MS. A recent study examined the records of 6,258 of these MS patients to determine how common benign MS is, to evaluate factors associated with BMS, to investigate the course of BMS over time, and to explore whether disease-modifying therapy with associated with BMS.
Patients in the registry were retrospectively classified as having BMS or non-BMS at baseline (entry into the registry) according to the three most commonly used criteria: EDSS ≤ 2.0 and disease duration (DD) ≥ 10 years (Criterion I), EDSS ≤ 3.0 and DD ≥ 15 years (Criterion II), and EDSS ≤ 3.0 and DD ≥ 10 years (Criterion III). Disease duration was measured as time since first MS symptoms, not necessarily diagnosis.
At baseline, 1,237 patients (19.8 percent) in the study cohort were classified as having BMS according to the strictest classification criteria (Criterion I). Similarly, 20 percent were classified as having BMS using Criterion II. In contrast, 33.3 percent were classified as having BMS when the least conservative criteria (Criterion III) was applied.
The majority of patients classified with BMS (95.6 percent) had relapsing-remitting MS, which means that relapses do not affect benign status, but degree of recovery may. Researchers discovered that patients with progressive MS and those of African-American race were less likely to have BMS at baseline. Of the 382 African-American patients included in the study, only 11.8 percent had benign MS.
Does benign MS stay benign?
After an average of four years, 511 patients (about 40 percent) who started out with benign MS continued to have BMS at study end; however, follow-up information was available for less than two-thirds of the study participants initially classified with BMS. Of the 788 BMS patients who completed the study, 35.2 percent had progressed to non-BMS status.
Does treatment affect benign MS?
At the beginning of the study, twice as many patients in the non-BMS group (81.8 percent) were using a disease-modifying therapy (DMT) than in the BMS group (40.8 percent). Study results show that use of DMT at the beginning and end of the study in the BMS group was associated with reduced risk of progressing to non-BMS status. Patients who started a DMT during the study were also less likely to progress. Unfortunately, the protective value of DMT use was lost for patients with BMS who stopped using a DMT, in which case their likelihood of progressing was equal to those who never used a DMT.
In this retrospective study of MS patients across New York state, researchers determined that use of DMT and longer disease duration were the only significant prognostic factors for continued benign MS status. This supports the National MS Society’s recommendation that early preventative treatment, even in the face of little to no disability, is important in reducing the risk of progression years down the road.
See more helpful articles:
Zivadinov R, Cookfair DL, Krupp L, et al. Factors associated with benign multiple sclerosis in the New York State MS Consortium (NYSMSC). BMC Neurology. 2016;16:102. doi:10.1186/s12883-016-0623-2.