| During Skull Base Surgery, the intracranial oculomotor nerve is frequently damaged, causing significant morbidity. Not only the oculomotor nerve shows the poorest results after repair, but also it is the nerve that lack repair methods. The complexity of the oculomotor nerve, misdirected regeneration, and nerve defect postinjury are the main reasons of its poor outcome after repair. For many years, end-to-end repair models, and even a nerve graft rat model for the oculomotor nerve repair in the cavernous sinus are performed, the problem of misdirected regeneration and nerve defect still exist. Although the peripheral nerve repair studies show that nerve conduit can bridge the nerve defects and benefit the selective regeneration, an anamial model of the nerve conduit repair the intracranial oculomotor nerve is lacking, and an experimental comparative study of intracranial oculomotor repair with biomemberane wrap, nerve graft, and nerve conduit has not yet been performed.Therefore, this study was designed to investigate oculomotor nerve regeneration after nerve conduit repair in comparison with nerve graft, and biomemberane wrap end-to-end repair in cats. Evaluation of the results was performed at 14 weeks postsurgery and included the pupil reflect test, along with light and transmission electron microscopy. Morphological study on the neurons of oculomotor nucleus was performed by HRP retragrade tracing method.Materials and Methods. A total of 32 cats, each weighting 2.6-3.5kg, were used in this experiments. In each cat, the cistern segment of the right oculomotor nerve was transected using microscissors within the cistern segment 1 mm before its entrance into the cavernous sinus, then the nerve repair was performed treated with the biomemberane wrap, nerve graft and nerve conduit method. The oculomotor nerves of other two cats werenot cut or cut without repair. At 14 weeks after the oculomotor nerve repair, 5 cats were selected randomly from each of the biomemberane wrap, peripheral nerve graft and nerve conduit repair groups, the medial rectus muscles of the operation sides were injected with 10% horseradish peroxidase (HRP), two contrast cats were traced with the same method. Two days later, the DAB straining method was used to morphological study on the brainstem of cats. The nerves (including the contralateral intact nerves) were removed for neuropathological examination. Morphometric analysis of the nerves was performed using specially computer software.Results. The operations were successful in all cats. The times cost in biomemberane wrap, nerve graft, and nerve conduit group were 4+2 min, 9 + 3 min, and 5 + 2 min, which was significantly longer in nerve graft group than that in biomemberane wrap, and in nerve conduit groups (p<0.05). Four cats died postsurgery, all the remaining cats did well postoperatively and had no signs of infection or neurological dysfunction except for total oculomotor nerve paresis. The function of the oculomotor nerves in 78% cases of biomemberane wrap, 67% cases of nerve graft, and 75% cases of nerve conduit repair groups showed gradual improvement with time, while didn't recovery in the contrast cats. Histological examination confirmed the anatomical continuity of the nerves in three groups of repair. The number of axons distal to the repair site was lower compared with those proximal, the ratios of nerve fiber transition in biomemberane wrap, nerve graft, and nerve conduit groups were 78.6%, 63.2%, and 81.5%. The ratio was lower in nerve group than that in two other groups (p<0.05). On histological studies, all nerves in three groups revealed axonal regeneration, with a large number of myelinated fibers in the distal nerve segments. The new axons had arelatively small diameter, thin myelinated. Statistical analysis revealed less myelinated axons in the nerve graft group, while the diameter of the axons was smaller in the nerve conduit group than that in other two groups. Sometimes, nonmyelinated axon was observed in direct contact with Scheann cells.
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