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Understanding MS

Declaration of sponsorship Novartis Pharma AG
Read time: 45 mins
Last updated:25th Oct 2022
Published:12th Aug 2021

Understanding Multiple Sclerosis

Multiple sclerosis

MS is an autoimmune disease characterised by inflammation and damage to the central nervous system (CNS). Common MS symptoms include impairments to cognition, walking, and balance; bladder or bowel dysfunction; abnormal tiredness; or visual disturbances1. The symptoms of MS are caused by peripherally driven inflammation and neurodegeneration of the CNS2-5.

MS is characterised by four disease courses or phenotypes6,7:

  • clinically isolated syndrome (CIS)
  • relapsing-remitting MS (RRMS)
  • secondary progressive MS (SPMS)
  • primary-progressive MS (PPMS)

The course of the disease is indicated by evidence of progression, active disease and relapses, and the extent and nature of disability7. PPMS differs in important ways from RRMS and SPMS, discussed below, and can be considered apart from relapsing forms of the disease6.

The onset of MS is typically marked by CIS, which is the first episode of neurological symptoms caused by inflammation or demyelination in the CNS. CIS, which must persist for at least 24 hours, does not yet satisfy diagnostic criteria for MS as people who experience CIS may or may not develop MS8. RRMS, however can develop from CIS3,4,6.

Approximately 85% of people with MS are initially diagnosed with RRMS8. RRMS is characterised by clearly defined episodes of new or increasing neurologic symptoms (‘relapses’, ‘exacerbations’), followed by periods of partial or complete recovery (‘remissions’)6. RRMS can be characterised as ‘active’ (with relapses and/or evidence of new magnetic resonance imaging [MRI] activity over a period of time) or ‘not active’, and ‘worsening’ (a confirmed increase in disability following a relapse), or ‘not worsening’6.

SPMS follows an initial relapsing-remitting course. Some people with RRMS transition to a secondary progressive course, which shows progressive worsening of neurologic function (accumulation of disability) over time. SPMS can be characterised as ‘active’ (with relapses and/or evidence of new MRI activity during a period of time) or ‘not active’, and ‘with progression’ (evidence of disability accumulation over time, with or without relapses or new MRI activity), or ‘without progression’7.

A standardised definition of SPMS has not been developed. Assessments that consider other manifestations of MS disability are required. Clinical tools are being developed for establishing a standardised assessment based on patient-physician discussions of clinical history9.

Following 6–10 years from MS onset, approximately 25%–40% of people with RRMS have progressed to SPMS, with a median time to transition ranging from 10 to 23 years10–13

PPMS is characterised by worsening neurologic function from symptom onset, without early relapses or remissions. PPMS can be described as ‘active’ (with an occasional relapse and/or evidence of new MRI activity over time), or ‘not active’, and ‘with progression’ or ‘without progression’6.

PPMS differs in important ways from relapsing forms of MS (RRMS, SPMS):

  • People with PPMS tend to have fewer brain lesions than people with RRMS or SPMS
  • Brain lesions in people with PPMS may contain fewer inflammatory cells
  • People with PPMS may exhibit more lesions in the spinal cord than in the brain
  • The average age of onset is approximately 10 years later in PPMS than RRMS or SPMS
  • People with PPMS commonly have more difficulty walking and remaining in the workforce than people with RRMS or SPMS

Approximately 15% of people with MS are diagnosed with PPMS8.

Overview of MS epidemiology

In 2020, approximately 2.8 million people worldwide had MS (Figure 1)14,15.


Figure 1. Number of people with multiple sclerosis per 100,000 worldwide, 2020 (Adapted14). MS, multiple sclerosis.

Onset of MS commonly occurs between the ages of 20–404. MS affects more women than men: 69% of people with MS are women, 31% are men14.

The prevalence of familial MS is approximately 11.8%16. Environmental and lifestyle risk factors include Epstein-Barr virus (EBV) infection in adolescence and early adulthood, tobacco exposure through active or passive smoking, low levels of vitamin D, a lack of sun exposure, and obesity during adolescence4,14.

Every 5 minutes, someone, somewhere in the world, is diagnosed with MS14

Continue to learn about the complex, unmet needs of people living with multiple sclerosis (MS), and how busy clinicians can meet these needs by following best-practice strategies

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Management of multiple sclerosis


Multiple sclerosis (MS) is an immune-mediated disease, caused by peripherally driven inflammation and neurodegeneration of the central nervous system (CNS)2-5.

As MS progresses, lesions in the CNS and the brain indicate advancement from neuroinflammation to neurodegeneration, leading to irreversible neuroaxonal degeneration, demyelination, and cumulative disability, diminishing mobility, cognitive decline, and loss of independence2-5.

MS disease phenotypes comprise clinically isolated syndrome (CIS), relapsing remitting (RRMS), secondary progressive (SPMS), and primary progressive (PPMS)6,7. Approximately 85% of people with MS are diagnosed with RRMS8. As described in the previous section, PPMS differs from relapsing MS phenotypes (RRMS, SPMS) in important ways. Almost 15% of people with MS are diagnosed with PPMS6.

Follow the link to learn some of the important differences between PPMS and relapsing forms of MS

The development of relapsing forms of MS, excluding PPMS, is shown in Figure 225.

Continue for figures and details on the main diagnostic criteria and methodology in multiple sclerosis

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