Scientists and medical professionals have not yet agreed upon a clear definition of aggressive multiple sclerosis (MS). However, doctors may use the term to refer to MS that progresses rapidly, involves frequent and severe relapses, and causes rapid and permanent disability.

MS is an autoimmune condition that affects the central nervous system (CNS).

This article provides a working definition of aggressive MS, as per the latest scientific research. It also outlines the features, symptoms, and complications of aggressive MS, and provides information on its diagnosis, treatment, and outlook.

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As the authors of a 2020 study explain, scientists and medical professionals have yet to agree upon a definition for aggressive MS. Medical professionals may use the term to refer to rapidly progressing MS, severe MS, or a disease that causes a high level of disability.

The authors of a 2020 review article suggest that aggressive MS is MS that presents with characteristics such as:

  • frequent and severe worsening of MS symptoms, which doctors refer to as “MS relapses
  • incomplete recovery from MS relapses
  • rapidly progressing and permanent disability

However, scientists do not yet agree on how to quantify the above measures.

To complicate matters further, the 2020 review article considers the terms “aggressive MS” and “highly active MS” interchangeable. However, a 2023 opinion article published in Frontiers in Neurology argues that some scientists use these two terms to refer to different forms of the disease.

Learn more about MS.

Since there is no formal definition of aggressive MS, scientists are not yet able to provide a list of its associated features and symptoms.

However, the 2023 Frontiers in Neurology article does list some common features of both “aggressive” and “highly active” MS. These are:

  • the occurrence of more than two relapses per year in people who have not received treatment
  • the occurrence of more than one relapse per year in people who have received treatment
  • evidence of more than two contrast-enhancing brain lesions on an MRI scan

According to a 2023 article, the following symptoms can worsen during an MS relapse:

Matthew’s story: Receiving a diagnosis of MS

“I was diagnosed with secondary progressive MS in 2020. My physical health has deteriorated rapidly since diagnosis; I was once previously fit and active, but I now walk with a walker and need assistance in many ways.

I am in some pain 24 hours a day despite taking medications such as baclofen, gabapentin, tizanadine, codeine, and tramadol. The pain comes from spasticity and neuropathy and can negatively impact my sleep hygiene.

This pain and sleep disruption can have an (unavoidable) knock-on effect on my mood and overall cheerfulness, but I try my best every day because I am blessed to have two wonderful children and a loving wife.”

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According to the 2020 paper, doctors may be able to determine whether a person has aggressive MS even before signs or symptoms appear. Potential signs of aggressive MS include:

  • at least two contrast-enhancing brain lesions, as indicated on an MRI scan either at the onset of the condition or during an early follow-up
  • 20 or more lesions on an MRI scan at the onset of the condition
  • higher levels of the protein “neurofilament light chain” in either the blood or the cerebrospinal fluid, which indicates damage to long nerve fibers called axons, either at the time of diagnosis or during follow-up

According to a 2020 review, there is currently no scientific agreement on how best to treat aggressive MS. In part, this is due to a lack of consensus regarding a suitable definition of the disease.

In general, MS treatments may include the following:

  • Medications to reduce relapse severity: High dose corticosteroids are the first-line treatment for short-term (acute) MS relapses. These medications work by suppressing the immune system and speeding up a person’s recovery in relapsing forms of MS.
  • Medications to reduce relapse frequency: Disease-modifying therapies (DMTs) aim to lower the amount of damage and scarring to the myelin sheath surrounding the nerves. DMTs may also help slow long-term disability, though further research is necessary to find how effective they are in the long term. Research has also suggested that DMTs can reduce relapses of MS.
  • Treatments to help manage symptoms: Managing symptoms may involve a mix of treatments, including medications and physical therapy.

MS is a serious condition that can cause multiple complications. These may include:

Due to a lack of scientific consensus regarding the definition of aggressive MS, it is difficult to give an accurate outlook for this disease.

As one 2020 review article explains, many scientists define aggressive MS as MS that leads to severe and rapidly increasing disability. The same article notes that some medical professionals use the term “malignant MS” to refer to aggressive MS that leads to significant disability or death within a relatively short time after its onset.

A person may consider speaking with their doctor for more information on their treatment options and outlook.

MS is an autoimmune condition that causes damage to the protective layers surrounding the nerves of the CNS. The condition can cause various symptoms and may result in mild to severe disability.

Scientists have yet to agree on a definition of aggressive MS. However, doctors may use this terminology to refer to MS that progresses rapidly, involves frequent and severe relapses, and causes permanent disability or death within a relatively short timeframe.

Medical experts have not yet established a specific treatment plan for aggressive MS, partly because there is no clear definition of the disease and its features. Anyone who has received a diagnosis of MS and is experiencing worsening symptoms of the disease may need to talk with their doctor. A doctor can offer insights into the person’s diagnosis, treatment options, and outlook.