MS is an exceptionally difficult disease to research for a number of reasons:

• The cause is unknown, though it is generally believed to be a combination of genetic, immunological and environmental factors. However, because it often takes many years for someone to be diagnosed, and because there are so many variables, it has so far been impossible to determine a specific cause or trigger.
  
• The effects are within two of the most inaccessible parts of the body, the brain and spinal cord. It is only since the advent of MRI, in the early 1980s, that scientists have actually been able to view the actual lesions within the brain and spinal cord.
  
• There is no single pattern to the disease, indeed there are four types of MS: relapsing-remitting, progressive relapsing, primary progressive and secondary progressive.
  
• The course of the disease is unpredictable. The number and position of lesions on a patient's central nervous system does not necessarily correlate with their relapse occurrence or level of disability. There are no definitive tests for the disease.