Multiple Sclerosis (MS) is a condition where the immune system mistakenly attacks the central nervous system, leading to inflammation and damage. Historically, the disease course was marked by uncertain disability accumulation. Modern medical advancements have fundamentally shifted this outlook, demonstrating that progression can often be halted or significantly slowed, leading to long periods of stability. Achieving this stable state relies heavily on early diagnosis and the prompt initiation of monitoring and intervention.
Defining Stability in Multiple Sclerosis
Understanding the difference between an MS “relapse” and “progression” is the first step in defining stability. A relapse is an acute flare-up of new or worsening neurological symptoms lasting at least 24 to 48 hours. Progression, in contrast, refers to the slow, steady accumulation of neurological disability over time, often independent of acute attacks, and is typically measured using the Expanded Disability Status Scale (EDSS).
Achieving true stability requires stopping both forms of disease activity: preventing acute relapses and halting the gradual accumulation of disability. Clinical stability means a person’s physical function, as measured by the EDSS, remains unchanged or improves over a sustained period. A key component in defining this state is the use of magnetic resonance imaging (MRI) scans, as MS-related inflammation does not always cause visible symptoms. Therefore, stability requires the absence of clinical worsening and no new or enlarging lesions visible on the brain and spinal cord scans.
The Goal of No Evidence of Disease Activity
The clinical target known as No Evidence of Disease Activity (NEDA) defines a state of comprehensive disease control by incorporating both clinical and imaging data.
The standard NEDA-3 criteria require that three distinct conditions are met over a specified time period: no clinical relapses, no confirmed disability progression (meaning the EDSS score has remained stable or improved), and no new or enlarging lesions visible on annual MRI scans.
The primary strategy for achieving and maintaining NEDA involves the use of Disease Modifying Therapies (DMTs). These medications target the underlying inflammatory and neurodegenerative processes that drive MS activity. Early diagnosis and prompt initiation of a highly effective DMT are strongly associated with higher rates of achieving NEDA.
Patients who maintain NEDA status have a significantly better prognosis and disability outcome years later. While NEDA-3 focuses on inflammation, more stringent definitions like NEDA-4 have been proposed to also include the absence of brain volume loss (atrophy) to better capture the neurodegenerative element of the disease.
Factors Influencing Long-Term Disease Cessation
While DMTs are fundamental, several patient characteristics and lifestyle choices influence the long-term likelihood of maintaining stability. The specific type of MS significantly impacts prognosis; individuals with Relapsing-Remitting MS (RRMS) generally have a better chance of achieving NEDA than those with Primary Progressive MS (PPMS).
Age is a significant prognostic factor, with an older age at MS onset often correlating with a faster rate of disease progression. A subset of individuals may have a naturally mild disease course, described as “Benign MS.” This term applies to patients who maintain a low level of disability (EDSS score of 3 or less) for at least 10 to 15 years after onset.
Lifestyle factors also play a supportive role in maintaining stability. Smoking is linked to a higher risk of converting to progressive forms and can increase disability rates. Cessation of smoking is a modifiable factor that may improve disability outcomes. Additionally, maintaining a healthy weight and engaging in regular exercise supports overall neurological health, helping sustain the stability achieved with DMTs.