Multiple sclerosis (MS) is a chronic, unpredictable disease of the central nervous system, namely the brain, spinal cord and optic nerves. The immune system incorrectly attacks myelin, the protective insulation surrounding nerve fibres. The myelin sheath and axon degenerates, making them look scarred or sclerotic, hence the name. Typically, patients suffer attacks, with acute worsening of neurological function (eg, fatigue, weak legs, numbness in the face, limbs or trunk, dizziness, slurred speech), followed by partial or complete recovery periods.