Multiple sclerosis (ms)

[Gregory]

In multiple sclerosis, patches of myelin (the substance that covers most nerve fibers) and underlying nerve fibers in the brain, optic nerves, and spinal cord are damaged or destroyed.

The cause is unknown but may involve an attack by the immune system against the body’s own tissues (autoimmune reaction).
In most people with multiple sclerosis, periods of relatively good health alternate with episodes of worsening symptoms, but over time, multiple sclerosis gradually worsens.
People may have vision problems and abnormal sensations, and movements may be weak and clumsy.
Usually, doctors diagnose multiple sclerosis based on symptoms and results of a physical examination and magnetic resonance imaging.
Treatment includes corticosteroids, drugs that help keep the immune system from attacking the myelin sheath, and drugs to relieve symptoms.
Life span is unaffected unless the disorder is very severe.

The term “multiple sclerosis” refers to the many areas of scarring (sclerosis) that result from destruction of the tissues that wrap around nerves (myelin sheath) in the brain and spinal cord. This destruction is called demyelination. Sometimes the nerve fibers that send messages (axons) are also damaged. Over time, the brain may shrink in size because axons are destroyed.
In the United States, up to about 914,000 people, mostly young adults, have multiple sclerosis. About 10,000 new cases are diagnosed each year.
Worldwide, more than 2 million people have multiple sclerosis.
Most commonly, multiple sclerosis begins between the ages of 20 and 40, but it can begin anytime between ages 15 and 60 years. It is somewhat more common among women. Multiple sclerosis is uncommon among children.
Most people with multiple sclerosis have periods of relatively good health (remissions) alternating with periods of worsening symptoms (flare-ups or relapses). Relapses can be mild or debilitating. Recovery during remission is good but often incomplete. Thus, multiple sclerosis worsens slowly over time.

[Renato]

Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness, spasticity, urinary dysfunction, and mild cognitive symptoms. Typically, neurologic deficits are multiple, with remissions and exacerbations gradually producing disability. Diagnosis requires clinical or MRI evidence of ≥ 2 characteristic neurologic lesions that are separated in both time and space (location in the central nervous system [CNS]). Treatment includes corticosteroids for acute exacerbations, immunomodulatory drugs to prevent exacerbations, and supportive measures.
(See also Overview of Demyelinating Disorders.)
Multiple sclerosis is believed to involve an immunologic mechanism. One postulated cause is infection by a latent virus (possibly a human herpesvirus such as Epstein-Barr virus), which, when activated, triggers a secondary autoimmune response.
An increased incidence among certain families and presence of human leukocyte antigen (HLA) allotypes (HLA-DR2) suggests genetic susceptibility.
MS is more common among people who spend their first 15 years of life in temperate climates (1/2000) than in those who spend them in the tropics (1/10,000). One explanation is that lower levels of vitamin D are associated with an increased risk of MS, and vitamin D levels correlate with the degree of sun exposure, which is lower in temperate climates. Cigarette smoking also appears to increase risk.
Age at onset ranges from 15 to 60 years, typically 20 to 40 years; women are affected somewhat more often.
Neuromyelitis optica spectrum disorder (Devic disease), previously considered a variant of MS, is now recognized as a separate disorder.