(45) Can Nerve Lateralization Mitigate the Risks of Inferior Alveolar Nerve Injury During Removal of Large Mandibular Cysts? A Retrospective Study

Abstract: Inferior alveolar nerve (IAN) injury can result in adverse patient outcomes, negatively impact quality of life, and can have legal ramifications. Large cysts of the mandible and associated impacted teeth predispose patients to nerve injury and pathologic fracture prior to, during, and after removal. The purpose of this study was to present the University of Rochester’s experience in minimizing the risk of IAN injury with large mandibular cysts. This retrospective study reviewed subjects diagnosed with mandibular cysts and treated by the University of Rochester Oral and Maxillofacial Surgery service at Strong Memorial Hospital (Rochester, New York) between 2023 and 2024. Inclusion criteria were: 1. Subjects aged ≥18 years at the time of treatment, 2. A mandibular cyst in the posterior body/angle region, 3. Presence of an impacted tooth, 4. Risk of IAN injury, and 5. Maxillofacial computed tomography (CT) or Cone-beam Computed tomography (CBCT) scan. Exclusion criteria were: 1. Subjects aged < 18 years of age at the time of treatment, 2. Cysts in other locations (maxilla, symphysis or parasymphysis of the mandible), 3. Malignant or non-cystic benign pathology, 4. History of ipsilateral IAN injury, mandibular surgery, neuropathic pain, and/or trigeminal neuralgia, 5. Failed three months follow up, and 6. Incomplete medical records. The primary predictive variable was the risk of IAN injury as defined by Rood’s criteria and evidence of ≥ 3 millimeters (mm) of IAN overlap with cyst and/or tooth on CT scan. The primary outcome variable was IAN functional sensory recovery (FSR) of S3-S4 on the Medical Research Council (MRC) scale at 3 months follow-up. Covariates were demographics, cyst size, degree of IAN overlap with the impacted tooth and the cyst, and incidence of pathologic mandible fracture. The study team designed a data collection sheet (Excel; Microsoft, Redmond, Wash.) to record information from electronic medical records and descriptive analysis was conducted. The steps of the operation were as follows: 1. Exposure of the mandible via transcutaneous approach, 2. With or without exposure and lateralization of the IAN using a titanium bone-guided custom nerve lateralization implant, 3. Cyst enucleation and curettage, 4. Tooth removal by sectioning and bone removal as indicated, 5. Prophylactic mandibular fixation by the placement of miniplates or reconstruction plate, as indicated, and 6. Closure of oral mucosa and skin with sutures. Eight patients were included in the case series (4 male, 4 female), with a mean age of 51 years old (range, 34-63). Mean cyst size was 46.46 cm3 (range, 16.97-87.27), mean overlap between IAN and impacted tooth was 12.71 mm (range, 0-9.1) and mean overlap between IAN and cyst was 22.65mm (range, 2.5-41.8). At the narrowest dimension, mean distance from impacted tooth to inferior border of the mandible was 6.14 mm (range, 0-14.1) and mean distance from cyst to inferior border of the mandible was 4.56 mm (range, 0-8.5). Preoperatively, n = 1(x) had an incomplete pathologic fracture of the buccal plate, and no patients suffered fractures during procedure or in the follow-up interval. All patients achieved FSR at the S3-S4 level on the MRC scale. In this cohort, lateralizing the IAN was a useful approach for preventing permanent neurosensory dysfunction for subjects with large mandibular cysts and impacted teeth demonstrating significant overlap with the nerve.References Kouhsoltani, Maryam, et al. “Mandibular Fracture Associated with a Dentigerous Cyst: Report of a Case and Literature Review.” Journal of Dental Research, Dental Clinics, Dental Prospects, vol. 9, no. 3, 16 Sept. 2015, pp. 193–198,Lee, Hanbin, et al. “Investigation of Postoperative Complications of Intrabony Cystic Lesions in the Oral and Maxillofacial Region.” Journal of Oral and Maxillofacial Surgery, vol. 77, no. 9, 1 Sept. 2019, pp. 1823–1831, https://doi.org/10.1016/j.joms.2019.03.022. Accessed 2 Sept. 2023.

Table 1: Cyst Dimensions and Inferior Alveolar Nerve Overlap (pg1)
Table 1: Cyst Dimensions and Inferior Alveolar Nerve Overlap (pg2)
Figure 1: (Above) Virtual surgical plan showing large cyst associated with teeth #31 and 32 with encasement of the IAN. (Middle) Clinical photographs showing surgical guide in place with lateralization of the IAN. (Below) The same patient after tooth and cyst removal.