Remyelination during optic nerve compression.

The structural changes produced in cat optic nerve by incremental chronic compression have been investigated by light and electron microscopy. Within the first week extensive demyelination occurred; some fibres underwent Wallerian degeneration and there was marked proliferation of astrocytic processes. After 5 weeks of compression remyelinated fibres were seen and occurred in all longer-term animals despite the maintenance of compression, but some partially and completely demyelinated fibres persisted. Myelin thickness had not returned to normal in the remyelinated fibres after 19 weeks and was often strikingly variable. The significance of these observations is discussed in the light of the recent demonstration of the restoration of central conduction by remyelination.