The specific cause of MS is not fully understood.Symptoms are caused by an abnormal inflammatory attack on the nerves of the brain or spinal cord. This inflammatory response may be triggered by genetic, environmental, and viral factors that initiate demyelination.
Demyelination is associated with an abnormalimmune system response that causes a type of white blood cell (called T cells) to attack myelin. Damage to the myelin then leads to sclerosis of nerve fibers in the central nervous system (CNS). The CNS has the ability to repair some of the damage but may not be able to achieve complete restoration. Exacerbations and remissions (common in multiple sclerosis) result from the intermittent damage and restoration.
A higher incidence of MS in certain geographical areas, such as the northern United States, suggests thatenvironmental factorsmay be involved, but none have been confirmed.
A specific viral risk factor has not been indentified, but exposure to a virusthat causes demyelination (especially prior to adolescence) may be a risk factor.