Inferior alveolar nerve-preserving mandibulectomy for nonmalignant lesions.

Abstract

INTRODUCTION Preservation or restoration of lip sensation is important in oral rehabilitation following ablative surgery. The lower lip is innervated by the inferior alveolar nerve, which provides unilateral sensation to the dentition and, through the mental nerve, to the labial mucosa anterior to the mental foramen and the skin from the commissure to the mental protuberance. The nerve is often sacrificed during segmental mandibulectomy resulting in lower lip anesthesia, which can predispose to problems such as drooling, impaired speech, and accidental biting of the lips. Bilateral sacrifice of the inferior alveolar nerve is particularly debilitating because it results in total lower lip anesthesia. Although restoration of the neurological deficit can be attempted with the use of nerve grafts to bridge the gap between the stumps of inferior alveolar nerve, the results are often less than satisfactory. When tumor control does not necessitate sacrifice of inferior alveolar nerve, as in some cases of benign tumors or osteoradionecrosis, attempts may be made to spare the nerve. Such an approach would obviate the need for additional effort at re-establishing sensation following mandibular reconstruction and may result in a better functional outcome. In the present report, we describe a technique for resecting the mandible while preserving inferior alveolar nerve function in two patients who required segmental mandibulectomy for nonmalignant lesions. SURGICAL TECHNIQUE The mandible is exposed by an intraoral or a transcervical approach or a combination of these, depending on the site and extent of the lesion. The first step involves exposing the mandible and identifying the mental nerve as it emerges through the mental foramen, which is located between the mandibular premolar teeth. In patients with edentulous, atrophic mandible the nerve’s relationship to the alveolar crest can be variable; it can occasionally lie over the alveolar crest. However, the distance from the inferior border remains constant throughout life. Therefore, it is safer to identify the nerve at a subperiosteal plane from the inferior border of mandible. The second step involves dissection to expose the mandibular canal and the neurovascular bundle. Circumferential dissection begins at the mental foramen with the use of surgical burrs. After a circular bony fragment is removed, the dissection continues along the remaining portion of embedded inferior alveolar nerve posteriorly until the point of planned vertical osteotomy is reached. With the mental nerve retracted slightly, the incisive branch of the inferior alveolar nerve is sectioned with knife and the proximal branch to the lower lip is left intact. This maneuver allows the nerve to be transposed from the mandibular canal to the cheek. The transposed inferior alveolar nerve can be anchored to the cheek flap using chromic sutures. This permits segmental resection of mandible without injuring the nerve.