In this disease there are areas of demyelinated white matter,called plaques,irregularly distributed throughout the brain and spinal cord. Grey matter in the brain and spinal cord may also be affected because of the arrangement of satellite oligodendrocytes round cell bodies. In the early stages there may be little damage to axons.
This disease appears to be an autoimmune disorder,possibly triggered by a viral infection,eg. Measles.
Environment before adolescence is implicated because the disease is most prevalent in people who spend their preadolescent years in temperate climates,and those who move to other climates after that age retain their susceptibility to MS.
Genetic factors are implicated too as there is an increased incidence to MS among siblings,especially identical twins,and parents of patients.
Effects of multiple sclerosis.
Damage leads to a variety of consequences,depending on the sites and sizes of demyelinated plaques,which damage white matter. This results in upper motor neurone dysfunction causing:
- Weakness of skeletal muscles and sometimes paralysis.
- Lack of coordination and movement.
- Disturbed sensation,eg.burning or pins and needles.
- Incontinence of urine.
- Visual disturbances,especially blurring and double vision. The optic nerves are commonly affected early in the disease.
