Re: what causes the myelin sheath to deteriorate?

Hi Sara,

I'm not quite sure what kind of deterioration you mean, but normally there are 
two cell types that produce myelin: schwann cells in the peripherial nervous 
system and oligodendrocytes in the central nervous system (brain and spinal cord 
area).  Normally myelin sheets (sheet, because it is wrapped like a sheet around 
the axon) recover after being injured by infection or mechanical stress 
(e.g. broken limb). There are also some myelin diseases, from which MS 
(multiple sclerosis) is the best known. So far experiments and research have 
taught us that the damage done to the myelin sheet in multiple sclerosis 
patients is primarily focused on myelin from the central nervous system, 
and that the damage is done by the patient's own immune system. 
In other words the immune system becomes confused and thinks that the myelin 
is a foreign body or invader, and tries to destroy it like it does with bacteria, 
viruses, or transplanted organs.

I hope I've answered you're  question 
Feel free to ask more 

Greetings 
David 
Amsterdam