Multiple Sclerosis

What is Multiple Sclerosis?

Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) caused by the immune system mistakenly attacking the myelin sheath (i.e. the protective coat around nerve fibers). Myelin is necessary for the transmission of nerve impulses through nerve fibres. The immune attack on the myelin results in inflammation, which further damages the myelin sheath, the cells that produce myelin, as well as the nerve cells themselves. If damage to myelin is slight, nerve impulses travel with minor interruptions; however, if damage is substantial and if scar tissue replaces the myelin, nerve impulses may be completely disrupted, and the nerve fibres themselves can be damaged.

MS is unpredictable and can cause symptoms such as extreme fatigue, lack of coordination, weakness, tingling, impaired sensation, vision problems, bladder problems, cognitive impairment and mood changes. Its effects can be physical, emotional and financial. 

What are the Types of Multiple Sclerosis?

The types of MS include:

  • Clinically isolated syndrome (CIS) – Clinically isolated syndrome involves one episode of symptoms lasting at least 24 hours. These symptoms are due to demyelination in the CNS. Typical symptoms of CIS are optic neuritis (experienced by poor vision, blind spots, double vision), transverse myelitis (experienced by muscle weakness, numbness, tingling, bladder issues) and Lhermitte’s sign (experienced by an electric shock feeling in the neck). There are two types of CIS episodes: monofocal and multifocal. A monofocal episode means one lesion causes one symptom. A multifocal episode means the patient has more than one lesion and more than one symptom. Note: although these episodes are characteristic of MS, they aren’t enough to prompt a diagnosis of MS.

    If lesions similar to those that occur with MS are present, a patient is more likely to receive a diagnosis of relapsing-remitting MS. If these lesions aren’t present, a patient is less likely to develop MS.

  • Relapsing-remitting MS (RRMS) – Relapsing-remitting MS involves clear relapses of disease activity followed by remissions. During remission periods, symptoms are mild or absent and there’s no disease progression. RRMS is the most common form of MS at onset and accounts for approximately 85% of all cases.

  • Primary progressive MS (PPMS) – In people with PPMS, neurological function becomes progressively worse from the onset of symptoms. Over time it becomes increasingly difficult for signals from the brain to get through to the rest of the body. The rate of progression can vary. It’s possible for people to maintain a steady state without new or worsening symptoms for extended periods. There are no clear relapses and remissions like those of RRMS. Common early symptoms of PPMS include weakness in the legs and problems with walking.

  • Secondary progressive MS (SPMS) – Secondary progressive MS occurs when RRMS transitions into the progressive form. A patient may still have noticeable relapses in addition to disability or gradual worsening of function.

Current Treatments and Unmet Needs

There is no cure for MS. Approved therapy for MS can be divided into several categories:

  1. Treatment of acute attacks

  2. Treatment with disease modifying agents that slow progression of the disease

  3. Treatment of MS symptoms

Currently there are no approved treatments that promote remyelination or neuronal repair. As a result, most patients with MS will, over time, experience progressive neurological and physical disability.5

Multiple Sclerosis Facts and Figures

  • In the US, there are approximately 913,000 people living with MS.1

  • Rates of MS are higher further from the equator. It’s estimated that in the southern US states (below the 37th parallel), the rate of MS is between 57 and 78 cases per 100,000 people. The rate is twice as high in northern states (above the 37th parallel), at about 110 to 140 cases per 100,000 people.2

  • RRMS is the most common type of MS. Approximately 85% of people receive an initial diagnosis of RRMS.2

  • Untreated, about 50% of people with RRMS will transition to SPMS within a decade of initial diagnosis.2

  • PPMS is diagnosed in about 15% of people with MS.2

  • The cost of living with MS depends on the degree of disability of the patient. One way to measure disability is through the Expanded Disability Status Scale (EDSS). Using the EDSS score, and the results from a 2016 study published on MS costs, Optum Rx estimated that:3,4

    • the cost for treating patients with mild to moderate disability (3.0 to 3.5 on the EDSS) is $30,000 per year;

    • the cost for treating patients with moderate disability (3.5 to 6.5 on the EDSS) is $50,000 per year; and

    • the cost for treating patients with severe disability (6.5 to 10 on the EDSS) is over $100,000 per year.


  1. Wallin, M.T., Culpepper, W.J., Campbell, J.D., Nelson, L.M., Langer-Gould, A., Marrie, R.A., Cutter, G.R., Kaye, W.E., Wagner, L., Tremlett, H., et al. (2019). The prevalence of MS in the United States. Neurology 92, e1029–e1040.Source: National MS Society and NCBI.
  2. Multiple Sclerosis Insight Report. Accessed March 17, 2020.
  3. Owens, G.M. (2016). Economic burden of multiple sclerosis and the role of managed care organizations in multiple sclerosis management. Am J Manag Care 22, s151-158.
  4. Hauser, S., and Josephson, S.A. (2016). Harrison’s Neurology in Clinical Medicine, 4th Edition (New York: McGraw-Hill Education / Medical).