Multiple sclerosis (MS) is a chronic disease of the central nervous system. It is thought to be an autoimmune disorder. It is an unpredictable condition that can be relatively benign, disabling, or devastating. Some individuals with MS may be mildly affected while others may lose their ability to see clearly, write, speak, or walk when communication between the brain and other parts of the body becomes disrupted.

Myelin is a fatty tissue that surrounds and protects the nerve fibers. Myelin is lost in multiple areas with MS. This loss of myelin forms scar tissue called sclerosis. These areas are also called plaques or lesions. When damaged in this way, the nerves are unable to conduct electrical impulses to and from the brain.

Causes of multiple sclerosis

There are many possible causes of MS, including the following:

• Viruses
• Autoimmune disorders
• Environmental factors
• Genetic factors

However, not enough is known about the role these factors play to definitively describe why a particular patient develops MS.

Symptoms of MS

The symptoms of MS can be erratic. They may be mild or severe, of long duration or short. They may appear in various combinations, depending on the area of the nervous system affected. The following are the most common symptoms of MS. However, each individual may experience symptoms differently.

Initial symptoms of MS may include:

• Burred or double vision
• Red-green color distortion
• Pain and loss of vision due to optic neuritis, an inflammation of the optic nerve
• Difficulty walking
• Paresthesia, which is an abnormal sensation such as numbness, prickling, or "pins and needles"

People with MS may experience some or all of the following symptoms to varying degrees. MS affects individuals uniquely, with each person's experience a different one.

• Muscle weakness in the extremities
• Difficulty with coordination (impaired walking or standing may result; partial or complete paralysis is possible)
• Spasticity – the involuntary increased tone of muscles leading to stiffness and spasms
• Fatigue (this may be triggered by physical activity, but may subside with rest; constant, persistent fatigue is possible)
• Loss of sensation
• Speech impediments
• Tremor
• Dizziness
• Hearing loss
• Bowel and bladder disturbances
• Depression
• Changes in sexual function

About half of all people with MS experience cognitive impairments related to their disease. The effects of these impairments may be mild, often detectable only after comprehensive testing, and may include difficulty with concentration, attention, memory, and judgment.