What is Multiple sclerosis

Multiple sclerosis (abbreviated MS, also known as disseminated sclerosis or encephalomyelitis disseminata) is an autoimmune condition in which the immune system attacks the central nervous system (CNS), leading to demyelination. It may cause numerous physical and mental symptoms, and often progresses to physical and cognitive disability. Disease onset usually occurs in young adults, is more common in women, and has a prevalence that ranges between 2 and 150 per 100,000 depending on the country or specific population. MS was first described in 1868 by Jean-Martin Charcot.

MS affects the areas of the brain and spinal cord known as the white matter. White matter cells carry signals between the grey matter areas, where the processing is done, and the rest of the body. More specifically, MS destroys oligodendrocytes which are the cells responsible for creating and maintaining a fatty layer, known as the myelin sheath, which helps the neurons carry electrical signals. MS results in a thinning or complete loss of myelin and, less frequently, the cutting (transection) of the neuron's extensions or axons. When the myelin is lost, the neurons can no longer effectively conduct their electrical signals. The name multiple sclerosis refers to the scars (scleroses - better known as plaques or lesions) in the white matter. Loss of myelin in these lesions causes some of the symptoms, which vary widely depending upon which signals are interrupted. However, more advanced forms of imaging are now showing that much of the damage happens outside these regions. Almost any neurological symptom can accompany the disease.

MS takes several forms, with new symptoms occurring either in discrete attacks (relapsing forms) or slowly accumulating over time (progressive forms). Most people are first diagnosed with relapsing-remitting MS but develop secondary-progressive MS (SPMS) after a number of years. Between attacks, symptoms may go away completely, but permanent neurological problems often persist, especially as the disease advances.

Although much is known about the mechanisms involved in the disease process, the cause remains elusive: the most widely-held being that the condition results from attacks to the nervous system by the body's own immune system. Some believe it is a metabolically dependent disease while others think that it might be caused by a virus such as Epstein-Barr. Still others believe that its virtual absence from the tropics points to a deficiency of vitamin D during childhood.

The disease does not have a cure, but several therapies have proven helpful. Treatments attempt to return function after an attack, prevent new attacks, and prevent disability. MS medications can have adverse effects or be poorly tolerated, and many patients pursue alternative treatments, despite the paucity of supporting scientific study. Many candidate therapies are still under investigation.

The prognosis, or expected course of the disease, depends on the subtype of the disease, the individual patient's disease characteristics, the initial symptoms, and the degree of disability the person experiences as time advances. Life expectancy of patients, however, is nearly the same as that of the unaffected population, and in some cases a near-normal life is possible.

Multiple sclerosis

Signs and symptoms

MS presents with a variety of symptoms, including changes in sensation (hypoesthesia), muscle weakness, abnormal muscle spasms, or difficulty in moving; difficulties with coordination and balance (ataxia); problems in speech (dysarthria) or swallowing (dysphagia), visual problems (nystagmus, optic neuritis, or diplopia), fatigue and acute or chronic pain syndromes, and bladder and bowel difficulties. Cognitive impairment of varying degrees, or emotional symptomatology in the form of depression or pseudobulbar affect are also common. Neuropathic pain is usual, and this can be in the form of Lhermitte's sign. The main clinical measure of disability progression and severity of the symptoms is the Expanded Disability Status Scale or EDSS.

The initial attacks (also known as exacerbations or relapses) are often transient, mild (or asymptomatic), and self-limited. They often do not prompt a health care visit and sometimes are only identified in retrospect once the diagnosis has been made based on further attacks. The most common initial symptoms reported are: changes in sensation in the arms, legs or face (33%), complete or partial vision loss (optic neuritis) (16%), weakness (13%), double vision (7%), unsteadiness when walking (5%), and balance problems (3%); but many rare initial symptoms have been reported such as aphasia or psychosis. Fifteen percent of individuals have multiple symptoms when they first seek medical attention. Optic neuritis or focal leg weakness may lead to falls and other serious accidents. For some people the initial MS attack is preceded by infection, trauma, or strenuous physical effort.