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Multiple sclerosis
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Multiple Sclerosis

Multiple sclerosis is a chronic condition characterized by immune-mediated damage to the myelin sheath in the central nervous system, leading to a wide range of neurological symptoms that vary significantly between individuals.

Overview

Multiple sclerosis (MS) is a condition characterized by areas of injury, known as lesions, in the central nervous system. These lesions are associated with damage to the myelin sheath, which is the protective covering that allows nerves to transmit impulses efficiently. The term “sclerosis” refers to the scar tissue that forms when the myelin sheath is damaged. These damaged areas can be visualized on a magnetic resonance imaging (MRI) scan.

The specific features and course of the disease vary widely among affected individuals. Signs and symptoms usually begin between the ages of 20 and 40. MS is broadly classified into two main categories:

  • Relapsing-remitting MS (RRMS): The most common diagnosis, characterized by periods of active symptoms (relapses) followed by periods of partial or complete recovery (remission).
  • Progressive MS: Diagnosed in up to 15 percent of individuals, this form is characterized by symptoms that gradually worsen over time without typical periods of relapse and remission.

Symptoms

Symptoms of MS can affect various parts of the body and cognitive functions. Common manifestations include:

  • Sensory disturbances: Prickling or tingling sensations (paresthesia), numbness, or pain in the arms, legs, or face.
  • Lhermitte’s sign: An electrical shock-like sensation running down the back and into the arms or legs, typically occurring when the head is bent forward.
  • Muscle control issues: Muscle stiffness (spasticity), weakness, or balance and coordination problems (ataxia), which can make standing and walking difficult. Some individuals may develop partial or complete paralysis.
  • Visual problems: Blurred or double vision, and optic neuritis (inflammation of the optic nerve), which can cause eye pain and vision loss.
  • Other neurological effects: Dizziness, poor bladder or bowel control, and difficulties with speech, concentration, memory, or judgment.

It is important to note that infections or fever can exacerbate the signs and symptoms of MS.

Causes & Risk Factors

MS is likely caused by a combination of genetic, environmental, and lifestyle factors. In people with MS, the immune system abnormally attacks the body's own tissues, triggering inflammation that damages the myelin sheath in the brain and spinal cord. Over time, nerve cells lacking myelin become more prone to damage and may die off, creating larger areas of injury in the nervous system.

Genetic Factors

Common genetic changes in or near hundreds of genes contribute to the risk of developing MS, many of which provide instructions for proteins involved in the immune system. Key genetic associations include:

  • HLA Complex: Changes in genes within the human leukocyte antigen (HLA) complex are associated with MS. These genes help the immune system distinguish between the body's own proteins and foreign invaders.
  • HLA-DRB1*15:01: The most well-established genetic risk factor is an allele of the HLA-DRB1 gene called HLA-DRB1*15:01. This gene provides instructions for making a protein that initiates an immune response. Researchers are currently investigating how this allele interacts with others to influence risk.

Environmental & Lifestyle Factors

Certain environmental and lifestyle factors are believed to increase the risk of developing MS, particularly when present during childhood or adolescence. These include:

  • Epstein-Barr virus infections
  • Lack of exposure to sunlight
  • Vitamin D deficiency
  • Obesity
  • Smoking and exposure to secondhand smoke

Inheritance

MS does not follow a clear inheritance pattern because it involves a complex interplay of genetic, lifestyle, and environmental factors. However, the risk of developing MS is higher for close family members of affected individuals than for the general population.

Frequency

An estimated 2.8 million people worldwide have MS. Approximately 2.1 in 100,000 people receive a diagnosis each year. The condition is more common in women and in white people of northern European descent.

Other Names

  • Disseminated sclerosis
  • MS

Frequently Asked Questions

Early MS symptoms often include sudden, unexplained numbness or tingling in a limb, blurred vision, or a brief loss of balance. Unlike a migraine or a simple nerve pinched in the neck, MS symptoms usually appear in a new area of the body, last longer than a few minutes, and may recur in different locations over time. If you notice these changes, especially if they come on suddenly and are not relieved by rest, it is wise to schedule an MRI and a neurological exam to rule out MS and other causes such as vitamin deficiencies or thyroid disorders.
Heat, dehydration, stress, and infections are common triggers that can intensify MS symptoms like fatigue, muscle spasms, or visual disturbances. To mitigate these effects, keep cool with fans or air conditioning, stay well hydrated, practice stress‑reduction techniques such as deep breathing or meditation, and seek prompt treatment for colds or flu. Wearing light, breathable clothing and avoiding prolonged exposure to hot tubs or saunas can also help.
DMTs reduce the frequency and severity of relapses by modulating or suppressing the immune system’s attack on myelin. The choice of drug depends on disease subtype, relapse history, side‑effect profile, pregnancy plans, and patient preference. For example, interferon beta is often used in early RRMS, while newer oral agents like fingolimod or dimethyl fumarate may be preferred for patients who need easier administration or have comorbidities. Your neurologist will weigh efficacy, safety, and your lifestyle to recommend the best option.
Regular, moderate exercise such as walking, swimming, or yoga can improve energy levels and muscle strength. Use assistive devices like canes or walkers when needed, and consider physical therapy for gait training. Prioritize sleep hygiene, avoid over‑exertion, and schedule rest periods during the day. Staying hydrated, using heat packs for muscle stiffness, and planning tasks around your peak energy times can also help you stay active without overtaxing your body.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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