What is multiple sclerosis?

Multiple sclerosis or MS is a disease that affects the brain and spinal cord resulting in loss of muscle control, vision, balance, and sensation (such as numbness). It is the commonest disabling neurological disease in young adults, and affects about 100,000 people in the UK. With MS, the nerves of the brain and spinal cord are damaged by one's own immune system. The condition is therefore called an auto-immune disease.

Auto-immune diseases are those whereby the body's immune system, which normally targets and destroys substances foreign to the body, such as bacteria and viruses, mistakenly attacks normal tissues. In MS, the immune system attacks the brain and spinal cord, the two components of the central nervous system. Other auto-immune diseases include systemic lupus erythematosus and rheumatoid arthritis.

The central nervous system is made up of nerves that act as the body's messenger system. Each nerve is covered by a fatty substance called myelin, which insulates the nerves and helps in the transmission of nerve impulses, or messages, between the brain and other parts of the body. These messages control muscle movements involved in movements such as walking and vision.

MS gets its name from the build-up of scar tissue (sclerosis) in the brain and/or spinal cord. The scar tissue or plaques form when the protective and insulating myelin covering the nerves is destroyed, a process called demyelination. Without the myelin, electrical signals transmitted throughout the brain and spinal cord are disrupted or halted. The brain then becomes unable to send and to receive messages properly. It is this breakdown of communication that causes the symptoms of MS.

Although the nerves can regain myelin, this process is not fast enough to outpace the deterioration that occurs in MS. The types of symptoms, severity of symptoms, and the course of MS vary widely, partly due to the location of the scar tissue and the extent of demyelination.

MS is two to three times as common in females as in males and it is unusual for it to occur before adolescence. A person has an increased risk of developing the disease from the teenage years to age 50 with the risk gradually declining thereafter.

What causes MS?

No one is sure what causes the body's immune system to go awry. Some scientists believe that it is a combination of genetics and something in the environment to which the person was exposed to early in life.

What are the symptoms?

Symptoms vary from person to person and can change over time in the same person. The most common early symptoms include:

• Muscle weakness
  
• Numbness and tingling
• Decreased co-ordination
• Blurred, hazy or double vision
• Eye pain

As the disease progresses, symptoms may include muscle stiffness (spasticity), pain, difficulty controlling urination, or problems with cognition.