At least for me, anyway.
I never really understood the blood-brain barrier part of the "mystery" until this past month when Cir had his follow-up exam at the Oak Clinic. Cir's doctor, Dr. Timothy Carrabine, has a unique way of explaining things that helps you see what's happening in your body in a way that's easy to understand.
First I will give the definition and then I'll try and explain it using Dr. Carrabine's storytelling version.
"...this is a membrane or cell layer which surrounds the blood vessels in the brain and keeps large molecules, white blood cells and other harmful substances from getting into the brain through the blood. Researchers think that in MS the blood-brain barrier is compromised. White blood cells somehow get through the barrier and into the CNS or central nervous system and causes the damage in the form of scars."
According to Dr. Carrabine, (and mind you, these are not his exact words, I'm paraphrasing), the barrier exists basically to keep things that can be harmful to the nervous system from getting into the brain.
In MS, the immune system is hyperactive and has developed bad white blood cells. These bad white blood cells are "sticky" and attach themselves to the blood vessels in the brain.
They then get through the barrier and into the central nervous system. Once there, they attack the myelin, and therefore damage the nerves. Scars are formed where the nerves try to repair themselves.
Some medications have been developed to try and deal with the bad white blood cells. Scientists think that copaxone changes the bad cells into good cells. This reduces the amount of damage to the CNS.
Even though the cells can still get through, they won't harm the myelin once they get into the brain.
Hopefully, this little explanation won't leave you mystified. You will at least know a little about it and be able to explain it to someone when they ask. Hey, they say the best way to learn something is to teach it to someone else. So, go for it!