Degeneration and regeneration processes in experimental facial nerve paralysis.

Facial nerve paralysis was provoked by compression of its extratemporal portion in rabbits and the degeneration and regeneration of the nerve fibres was studied ultrastructurally. The compression was removed to study the regenerative process in one group of animals. Axonal and myelin degeneration were the first events seen as a collagen tissue proliferation from the endoneurium and perineurium. Ultimately all the nerve was transformed into fibrous tissue. The myelin was disintegrated by Schwann's cells without any macrophagic activity. The regeneration process begins by the axons, that are orientated towards Büngner's bands of remnants of the Schwann's cells, in which a new myelin sheath appears. Schwann's cells play an important role, in both the degeneration and the regeneration process. The final aspect of the regenerated fibres is similar to normal but they contain more collagen tissue, thinner myelin sheaths, and a greater proportion of unmyelinated fibres.