How does Multiple Sclerosis cause demyelination

How does Multiple Sclerosis cause demyelination? 

The demyelination is largely an inflammatory process.

Lymphocytes, macrophages, and other immunocompetent cells accumulate around venules focally in the central nervous system and exit into the brain, attacking and destroying the local myelin, in what appears to be an autoimmune process.

In many patients with MS, a more degenerative (and poorly understood) pathology appears, with less inflammation and more generalized atrophy.