Remyelination during optic nerve compression.

An inflatable silicone rubber balloon implanted in the orbit has been used to simulate an expanding orbital tumour. The changes produced in the compressed cat optic nerve have been investigated by light and electron microscopy. Within the first week extensive demyelination occurred; some fibres degenerated completely and there was marked proliferation of astrocytic processes. Some partially and completely demyelinated axons were seen throughout the period studied but after 5 weeks many axons had become remyelinated. Remyelinated fibres were seen in all longer-term animals despite the continued presence of the orbital mass. The significance of these observations is discussed in the light of the physiology of conduction in demyelinated and remyelinated central axons.