Sural Nerve Cable Grafting Allows Regeneration in a 30-mm Complex Branching Facial Nerve Defect in a Large Animal Model
Mario A Aycart, M.D; Muayyad Alhefzi, M.D; Ericka M Bueno, PhD; Bohdan Pomahac, M.D
Brigham and Women's Hospital, Boston, MA
Introduction: The gold standard for repairing a nerve gap remains the autologous nerve graft. In facial nerve reconstruction, this is most commonly referred to as interposition or “cable grafting”. Rodent models have shown cable grafting to be equivalent to primary repair in facial nerve reconstruction. To our knowledge, there are no large animal models evaluating the feasibility of cable grafting to address a large gap, complex nerve defect. This study aims to evaluate the sural nerve as a suitable autologous nerve graft in reconstructing a 30-mm complex branching facial nerve defect in a large animal model.
Method: Yucatan miniature swine (n = 5) underwent transection of the inferior division of the facial nerve. The inferior division of the facial nerve was sharply transected at a point 5mm proximal to the branching point of the marginal mandibular and cervical nerve branches. Approximately 25mm distal to the transection, the marginal mandibular and cervical nerves were isolated and sharply transected to create a 30mm nerve gap. Sural nerves were concomitantly harvested from ipsilateral (same side of facial dissection) extremities. Gross electrophysiologic assessments were performed at study end point (24 weeks) to assess functional recovery by direct distal nerve stimulation prior to nerve harvest. Muscle-specific movement (e.g., lip and angle of the mouth depression for the marginal mandibular nerve and lateral neck flexion for the cervical nerve) was considered a positive test at 2mA of electrical stimulation. Distal nerve stumps were harvested for immunohistochemical evaluation using neurofilament and S100 to observe the distribution and presence of Schwann cells in the respective nerve fibers.
Results: After 24 weeks, sural nerve cable grafting was able to provide functional marginal mandibular and cervical nerves across a 30mm branching nerve gap. Functional recovery, as measured by positive, muscle-specific movement was present in all animals. Distal nerve stumps demonstrated appreciable co-staining for neurofilament and S100 indicating the presence of Schwann cells.
Conclusion: To our knowledge, this is the first study to evaluate the sural nerve as an autologous nerve graft in a large gap, complex facial nerve defect in swine. This study demonstrates the feasibility in establishing a 30-mm complex branching nerve defect model in swine. Furthermore, this study adds to the existing literature of the sural nerve's role in facial nerve reconstruction.
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