Rapid Intraoperative Facial Nerve Expansion

Abstract

The repair of nerve length defect presents a reconstructive challenge after trauma and oncologic resection. This study examined rapid intraoperative nerve expansion as a method of repairing nerve length defects with the cat facial nerve model. We compared expanded nerves with grafted nerves and intact nerves 1 year after repair using the criteria of gross function (symmetry and blink reflex according to a modified House scale), electromyography thresholds, nerve-conduction velocity, morphology, and axon count. Three of the five expanded nerves regenerated, and all of the grafted nerves regenerated. Functional results were similar for the regenerated expanded and the grafted facial nerves, and both methods achieved an equivalent level of function. The facial nerves of the regenerated expanded group, grafted group, and intact group had mean electromyography thresholds of 132 mV, 98 mV, and 134 mV, respectively, and mean conduction velocities of 48.3 mg/second, 47.9 m/second, and 44.7 m/second, respectively. Morphologic examination of all five expanded nerves immediately after the expansion process revealed an intact fascicular structure. However, 1 year after excision of the expanded segment and repair, only three of the five nerves regenerated. Axon count at 1 year was as follows: 404 for the regenerated expanded nerves, 449 for the grafted nerves, and 403 for the intact nerves. The potential advantages of rapid intraoperative nerve expansion over nerve grafting for the repair of nerve gap defects include a single suture line and absence of donor site morbidity. This pilot study demonstrates that rapid intraoperative nerve expansion and regeneration is possible and can be used to repair a nerve length deficit. The development of a rapid and reliable method of intraoperative nerve expansion deserves further study.