The exact cause is unknown, but most experts believe that MS is an autoimmune disease. This means that the body's defenses, called the immune system, mistakenly attack normal tissues. In MS, the immune system attacks the optic nerves, brain and spinal cord.
Many factors underlie the risk of MS. Over 200 genes have been implicated in MS, each of which contributes a small amount to susceptibility. Environmental exposures also play a role. MS is more common in those who grow up in colder regions, located far from the equator.
Your risk for MS is influenced by:
Geographic location or where you lived during childhood (up to age 15). People who spend the first 15 years of their lives in colder climates that are farther away from the equator are more likely to get MS than people who live closer to the equator during those years.
Family history of MS. About 15 out of 100 people who have MS have a relative with MS. The lifetime risk of MS in first-degree relatives of people with MS is 2 – 4%. This is approximately 7 – 10 times higher than the risk of the general population.
Genetic make-up. More than 230 genes have been discovered that each increase the risk of developing MS to a small degree. No one gene directly causes MS itself; someone with MS is likely have a combination of many of these MS-associated genes. Most of the MS-related genes that have been identified are known to play a primary role in immune responses. This supports the belief that MS is an autoimmune disease.
Race. People of Western European ancestry are more likely to get MS. However, MS can occur in any race.
Sex. RRMS is 2 – 3 times as common in women as in men.
Viral infection. First-time exposure to Epstein-Barr virus (the virus that causes infectious mononucleosis or “mono”) as an adult, may increase the risk of developing MS. MS relapses are more likely to occur during upper respiratory tract infections.
Habits and lifestyle. A low serum level of vitamin D may increase the chance of developing MS. Cigarette smoking is associated with a more severe course of MS.
Symptoms depend on which parts of the central nervous system have been damaged and the extent of that damage. Symptoms may last from days to months and then wane or resolve (relapsing-remitting) or persist and slowly worsen over time (disease progression). Some symptoms of MS are chronic, and fluctuate hour to hour, or day to day (for example fatigue, memory difficulties or muscle spasms). An increase in body temperature and/or an infection can sometimes cause old symptoms to reappear or worsen temporarily.
Common symptoms of MS include:
Muscle or motor symptoms, such as weakness in one or more limbs; foot drop/leg dragging; stiffness and cramping of the muscles (spasticity); weak hand grip; a feeling of leg heaviness
Visual symptoms, such as blurred, foggy or hazy vision in one or both eyes; dulled color vision; pain behind, or at the corner of, an eye (often triggered by eye movement); blindness; double vision. Optic neuritis—diminished vision in one eye that is often painful—is a fairly common first symptom of MS
Sensory symptoms, such as tingling; pins-and-needles sensations; numbness (a lack of feeling) in one or more limbs; a band of tightness around the chest or abdomen; burning pains or hypersensitivity to temperature or touch; stabbing facial pain; or electrical sensations down the neck or back that are triggered by looking down
Incoordination and imbalance, such as unsteady walking and frequent falling; veering to one side; loss of hand/finger dexterity; deterioration of handwriting; vertigo (room spinning); and tremor
Gait impairment, caused by leg strength and/or balance problems that may make walking difficult. Assistive devices, such as a cane, brace, rollator or wheelchair, may be needed some or all of the time
Bladder symptoms, such as an inability to hold urine (urinary incontinence), completely empty the bladder and/or sense bladder fullness
Constipation and other bowel disorders
Male erectile dysfunction (impotence) and female sexual dysfunction
Difficulty with swallowing; choking on liquids or solids
Slurred or uneven speech
Cognitive and emotional problems, including memory loss; difficult multi-tasking; and uncontrollable crying or laughing. These are more common in people who have had MS for some time. Depression is more common among people with MS that in the general population.
Feeling very tired (fatigue). Fatigue is one of the most common symptoms of MS. It can be worse if symptoms such as pain, spasticity, bladder symptoms, anxiety, or depression make it hard to sleep, but can occur even in the absence of sleep problems.