COMPARISON OF RABBIT FACIAL-NERVE REGENERATION IN NERVE GROWTH-FACTOR- CONTAINING SILICONE TUBES TO THAT IN AUTOLOGOUS NEURAL GRAFTS

Previous reports suggest that nerve growth factor (NGF) enhanced nerve regeneration in rabbit facial nerves. We compared rabbit facial nerve regeneration in 10-mm silicone tubes prefilled with NGF or cytochrome C (Cyt C), bridging an 8-mm nerve gap, to regeneration of 8-mm autolo gous nerve grafts. Three weeks following implantation, NGF-treated reg enerates exhibited a more mature fascicular organization and more exte nsive neovascularization than Cyt C-treated controls. Morphometric ana lysis at the middle of the tube of 3- and 5-week regenerates revealed no significant difference in the mean number of myelinated or unmyelin ated axons between NGF- and Cyt C-treated implants. However, when the numbers of myelinated fibers in 5-week regenerates were compared to th ose in their respective preoperative controls, NGF-treated regenerates had recovered a significantly greater percentage of myelinated axons than Cyt C-treated implants (46% versus 18%, respectively). The number of regenerating myelinated axons in the autologous nerve grafts at 5 weeks was significantly greater than the number of myelinated axons in the silicone tubes. However, in the nerve grafts the majority of the axons were found in the extrafascicular connective tissue (66%). The m ajority of these myelinated fibers did not find their way into the dis tal nerve stump. Thus, although the number of regenerating myelinated axons within the nerve grafts is greater than that of axons within sil icone tube implants, functional recovery of autologous nerve graft rep airs may not be superior to that of intubational repairs.