Studies performed under 89-N-0045 are primarily designed to examine the natural history of multiple sclerosis (MS) and its mimickers, viewed through the window of imaging (especially magnetic resonance imaging or MRI). The protocol has four other important objectives: (1) Screening prospective participants in selected Neuroimmunology Branch clinical trials; (2) Performing studies to help define the mechanism of action and cause of side effects of disease modifying therapies (DMT); (3) Studying healthy volunteers for comparison with patients and for development of new experimental technologies; and (4) Comparing MS to other neurological diseases that share imaging features.