Courtesy of Intermountain Medical Imaging, Boise, Idaho.

Multiple sclerosis (MS) is a chronic neurological disease of the central nervous system, specifically involving the brain, spinal cord, and optic nerves. The brain, spinal cord, and optic nerves are connected to one another by nerve fibres. A protein coating called myelin surrounds and protects the nerve fibres. Myelin can become inflamed or damaged. This is called demyelination. In MS, immune cells from blood vessels enter the brain, spinal cord, or optic nerves and cause areas of inflammation, demyelination, and nerve damage. These damaged areas are called lesions or plaques.

Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. For an MRI test, the area of the body being studied is placed inside a special machine that has a strong magnet. MRI can be used to look for problems in the brain, such as lesions or plaques caused by MS.