ase that we've just really looked at recently, and the degenerative component often occurs when people get progressive disease, and these medications that I'm going to talk about may not be very effective. It may be hard to help people with the current medications.
We used to tell people that well, you have an attack, and then you get better, and then everything's fine, and a few years later you may have another attack. That was wrong. Between attacks, there's continuous damage in most patients. For every attack I see in my office, there are ten attacks on the MRI, for example.
We also would tell people before we had treatments that, "Well, you've got multiple sclerosis. It comes and goes, but you look pretty good. You know, you'll be okay. You know, you look great." Because we didn't have any treatments, we wanted to keep people's spirits up. It wasn't true. Most people who start off with relapsing-remitting end up having progressive MS.
Dr. Ransohoff, maybe you could take us through your slides and explain to us why it's important to discuss and to differentiate the visible and invisible signs of MS.
The definition of multiple sclerosis is that it's an immune mediated demyelinating disease of the central nervous system. To amplify on that a little bit, the immune system, which is the body's immune defense system, composed of circulating white blood cells and factors, is what causes the damage in MS. The myelin, or insulation around nerve fibers in the central nervous system, is damaged, causing the fibers, which are like wires, not to work as well as they should. The central nervous system, which is where the disease occurs, includes the brain, the optic nerves and the spinal cord.
Now, I'm going on slide three, the typical clinical features of MS.
We think of the symptoms of MS as either being visible or invisible. Visible symptoms are symptoms that other people can see and can tell that a patient is having di...