The disease course for multiple sclerosis (MS) varies from person to person and depends partly on the type of MS a person has. Understanding MS can help people to gain better control of their individual treatment options and outlook.

MS is an immune-mediated disease in which the immune system mistakenly attacks the protective myelin sheath surrounding the brain and spinal cord. Damage to the myelin sheath disrupts nerve signals traveling to and from the brain, potentially causing both physical and cognitive symptoms.

This article describes what MS is, including its symptoms, causes, and types. We list some related conditions that have symptoms and pathologies similar to MS. We also describe the outlook for people living with MS and outline some frequently asked questions about the disease.

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MS occurs when the immune system mistakenly attacks the myelin sheath that surrounds and protects the central nervous system (CNS). The CNS consists of the brain and spinal cord.

Damage to the myelin sheath interferes with nerve signals traveling to and from the brain. This interference can result in a range of symptoms, including:

The symptoms of MS may differ from person to person. An individual’s symptoms may also differ in intensity, duration, and frequency.

People of any age may develop MS, though the disease is most common in people between the ages of 20 and 50.

MS is a progressive disease, meaning it worsens over time. Around 85% of people with MS present with a relapsing-remitting form of the disease, in which symptoms initially wax and wane before developing into a more progressive disease type.

The following factors can affect the treatment plan and outlook for people with MS:

  • symptom type and severity
  • disease type and progression
  • complications of MS

Understanding MS gives people greater control over their treatment and provides a sense of empowerment.

MS is a progressive disease, meaning a person may experience only a few mild symptoms initially, followed by new or worsening symptoms over time.

Common early symptoms of MS include:

  • numbness
  • tingling
  • muscle spasms
  • weakness
  • balance problems
  • dizziness
  • vision problems
  • fatigue
  • bladder issues
  • sexual problems
  • difficulties with memory or learning

The first time that a person experiences the onset of symptoms that could be due to multiple sclerosis lasting at least 24 hours is known as clinically isolated syndrome (CIS). CIS occurs due to swelling or demyelination of the CNS. Demyelination refers to the loss of the myelin sheath that surrounds the CNS.

Symptoms of a CIS episode could include:

  • Lhermitte’s sign, which is a tingling or shock sensation down the neck and back when a person bends their neck forward
  • numbness
  • muscle weakness
  • eye pain
  • vision problems

CIS is not always indicative of MS because a person with CIS may make a full or partial recovery. If brain lesions characteristic of MS accompany CIS, the person has a high likelihood of developing MS. However, if such brain lesions do not accompany CIS, the person has a much lower likelihood of developing MS.

Learn more about the early symptoms of MS here.

The symptoms of MS may intensify over time. A person can also develop new symptoms.

Some people may develop complications related to MS. Examples include:

Experts do not know the exact cause of MS. However, they do have several theories about potential MS triggers.

Some possible MS triggers include:

  • Immunological factors: Different cells in the immune system may contribute to MS
  • Infectious factors: Catching certain viruses in childhood may contribute to the development of MS in later life. One example is the Epstein-Barr virus.
  • Environmental factors: Some potential environmental triggers for MS include:
  • Genetic factors: Experts have not identified a single gene that will cause a person to develop MS. However, a person is more likely to develop MS if they have a family member who has the disease. This suggests that some people may have a genetic predisposition to the disease that requires an environmental trigger in order to develop.

Learn more about MS and genetics here.

According to the National Multiple Sclerosis Society (NMSS), doctors cannot predict how MS will progress in an individual.

To help classify MS, the International Advisory Committee on Clinical Trials of MS has defined four distinct types. The NMSS describes these types as follows:

  • Clinically isolated syndrome (CIS): The first episode of neurologic symptoms that occurs due to inflammation and demyelination of the CNS. Although CIS is characteristic of MS, it does not meet the criteria for a diagnosis of MS. This is because people with CIS may or may not go on to develop MS.
  • Relapsing-remitting MS: This type involves periods of relapse or “attacks” in which existing symptoms worsen or new symptoms develop, followed by periods where symptoms subside with full or partial recovery. Between attacks, the disease does not progress or worsen.
  • Secondary progressive MS: This type can follow relapsing-remitting MS in some cases. It involves a progression of the disease with or without relapses or new MRI activity.
  • Primary progressive MS: This type involves a gradual and steady progression of disability from the initial onset of MS symptoms, with few or no relapses or remissions. Around 10–15% of people have primary progressive MS.

Doctors can use the different types of MS to help guide a person’s individual treatment plan.

Several conditions are related to MS and may share similar symptoms or pathologies.

Some related conditions include:

MS does not necessarily mean a person cannot live a full, mostly active life. Modern treatments in combination with appropriate lifestyle changes can help reduce symptom severity and improve a person’s overall quality of life.

A person living with MS has an overall life expectancy that is around 95% that of an otherwise healthy individual.

Several factors can affect a person’s life expectancy and outlook. Indications of a favorable outlook include:

  • being female
  • experiencing a long duration between first and second relapses
  • having a relapsing form of the condition
  • experiencing mild relapses of symptoms
  • experiencing a complete recovery between relapses
  • mainly experiencing sensory symptoms
  • having a small number of brain lesions visible on MRI scans

Indications of a less favorable outlook include:

  • being male
  • experiencing several relapses in the first few years following diagnosis
  • having a progressive form of the condition
  • experiencing shorter durations between relapses
  • experiencing an incomplete recovery between relapses
  • involvement of multiple neural systems
  • involvement of the motor system, cerebellum, bladder, or bowel
  • having a large number of brain lesions and brain shrinking visible on MRI scans

Learn more about the outlook for people with MS here.

Below are some frequently asked questions about MS.

How many people have MS?

Around 1 million people in the United States are living with a diagnosis of MS. Worldwide, the total number is around 2.3 million.

Who gets MS?

Anyone can develop MS, but some factors increase a person’s risk, including:

  • Gender: Incidence is higher among females than males.
  • Race: White people have a higher incidence rate in comparison with people of other ethnicities.
  • Genetics: Having a parent with MS increases a person’s risk of developing the condition.
  • Environmental factors: Experts have linked MS risk to smoking, obesity, and vitamin D deficiency.
  • Geography: MS is more common in parts of the world furthest from the equator but also very rare in certain populations, suggesting that where a person lives can influence the risk of them developing the condition.

Does MS always cause paralysis?

MS does not always cause paralysis. Around 2 in 3 people with MS will maintain their ability to walk either independently or with an assistive device.

Is MS contagious?

Multiple sclerosis is not contagious, meaning a person cannot pass the disease on to another person.

MS is an immune-mediated disease in which the immune system mistakenly attacks the protective myelin sheath surrounding the CNS. Damage to the CNS disrupts nerve signals traveling to and from the brain, resulting in a range of physical and cognitive symptoms.

The disease course for MS varies according to the type a person has.

While there is no cure for MS, modern treatment options and lifestyle changes have improved both life expectancy and quality of life for people living with the disease. Having a good understanding of MS can help people take better control of their treatment and life.

To discover more evidence-based information and resources for multiple sclerosis, visit our dedicated hub.

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