Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS). Focal inflammatory lesions damage myelin, the insulating material that allows rapid nerve conduction. Later or ongoing injury to the axon itself, the nerve fibre, contributes to persistent disability and progression. Lesions can occur in different CNS regions, including the optic nerves, brain, brainstem, cerebellum, and spinal cord. Their location determines the clinical picture. A person may have painful monocular visual loss from optic-nerve involvement, numbness or weakness from a spinal-cord lesion, diplopia from brainstem disease, or ataxia from cerebellar involvement. Fatigue, impaired concentration, mood changes, bladder dysfunction, constipation, and sexual dysfunction may accompany the neurological deficits. The scattered distribution of lesions explains why MS does not produce one fixed neurological pattern. Symptoms may come and go, affect one side more than the other, or change over time. Relapsing disease produces episodes of new or worsening neurological dysfunction followed by partial or substantial recovery. Primary progressive MS instead causes gradual accumulation of disability from the outset, although it may still show active inflammatory disease. A useful clinical distinction...