Until recently, Wallerian Degeneration was thought to be rare in MS. This is important new information.
Wallerian Degeneration is a common and well-known process that occurs when a nerve fiber is damaged. We see this process in ischemic stroke, vasculitis and many neurodegenerative diseases. First, the axons die due to injury (loss of oxygen, iron deposition or injury.) Next, the myelin is "cleaned up." Then the oligodendrocytes die.
The oligodendrocytes in the central nervous system need axonal signals to survive. When the nerves cease to function, the oligos die. Cleaning up the myelin debris is a natural part of the process of Wallerian Degeneration.
The doctors studying CCSVI are now discussing Wallerian Degeneration as the potential method of injury to axons, and the reason why progressive MS is not as responsive to treatment. Wallerian degeneration can continue for years after the initial injury.
Here is the complete abstract of the study Squiffy linked:
Here is a study from 2007 discussing demyelination in relationship to Wallerian degeneration:
I see it as yet another link to ischemic injury and stroke, and another blow to the theory that MS is immune activated--but that's my opinion-