Multiple sclerosis (MS) is an autoimmune disease that affects the brain and spinal cord. In MS, the body's white blood cells attack tissue called myelin sheath.
Myelin sheaths are the protective covering for nerve fibers in the brain. Much like an electric wire is insulated with rubber or plastic, the myelin sheaths cover nerve fibers as they transmit nerve impulses within the brain.
When a myelin sheath is worn down or destroyed, the process is called demyelination. Demyelination causes the nerve fiber to be exposed. The exposed nerve fiber is less able to transmit nerve impulses. As a result, messages between different parts of the body are not transmitted as effectively.
After the myelin is destroyed, scar tissue called sclerosis is left behind in the damaged areas, which are referred to as lesions or plaques.
Who Gets MS?
MS affects over 400,000 people in the United States and up to 2.5 million people worldwide. Since most people are diagnosed before they turn 30, MS has been called the most common disability-causing illness for people under 45-years-old.
Gender and race also play a role in who gets MS:
Women are 70% more likely to have MS than men.
People of European descent are twice as likely to have MS as African Americans and Asian Americans.
Diagnosing MS
MS is often difficult to diagnose because symptoms are different for everyone. People who are diagnosed with MS usually have had a history of symptoms that come and go. Some tests that doctors may use to help them diagnose MS are:
Magnetic resonance imaging (MRI)
Spinal fluid testing
Evoked potentials (measuring how long it takes nerves to react to stimulation)
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