Outcome of Facial Nerve Integrity After Parotid Gland Surgery With and Without Intraoperative Monitoring: A Ten-Year Retrospective Study

Abstract

Background: Facial nerve injury is one of the most concerning complications of parotid gland surgery, with temporary and permanent dysfunction rates varying widely in the literature. This study aimed to identify factors associated with facial nerve injury during surgery for benign parotid tumors and assess the protective efficacy of intraoperative nerve monitoring (NIM) in preventing nerve injury. Methods: This retrospective study analyzed 329 patients who underwent parotid gland surgery between 2010 and 2023. Data collected included patient demographics, tumor characteristics (size, location, histology), surgical parameters (operation time, NIM usage), and postoperative nerve function evaluated using a modified House-Brackmann scale. Descriptive and inferential statistical analyses, including Chi-square tests and logistic regression, were employed to identify predictors of facial nerve outcomes. Results: Facial nerve injury occurred in 5.2% of patients, comprising 4.6% temporary and 0.6% permanent damage. Tumors located in the deep and inferior lobes significantly increased the risk of facial paralysis/palsy (p = 0.035), while tumor size and histology showed no significant associations. Using NIM significantly reduced the risk of facial nerve injury (p < 0.05; OR: 0.35, 95% CI: 0.25-0.50). Age was also identified as a significant predictor of nerve dysfunction (p < 0.05). Conclusions: The findings emphasize the importance of NIM in mitigating facial nerve injury, especially in anatomically complex tumor locations. Tailored surgical approaches based on tumor location and patient-specific factors, combined with the routine use of NIM, are recommended to optimize nerve preservation and improve postoperative outcomes.

Keywords: benign parotid tumor; facial nerve; intraoperative nerve monitoring; parotid gland surgery; postoperative facial nerve injury.

Figure 1

Correlation heatmap: This heatmap visualizes the correlation coefficients between key variables related to facial nerve injury after parotidectomy. Positive correlations are shown in warm tones (red), and negative correlations in cool tones (blue). Variables such as age, tumor size, operation time, and facial injury are compared. A moderate correlation between tumor size and operation time is evident, while weaker correlations exist between other variables. This visualization highlights how various factors interact in the dataset.

Figure 2

Logistic regression odds ratios for predictors: This figure illustrates the odds ratios (ORs) with 95% confidence intervals for key predictors of facial nerve injury following parotidectomy. Each point represents the odds ratio for a specific predictor variable. A red dashed line at OR = 1 marks the threshold of no effect. Variables with OR > 1 increase the likelihood of facial injury, while OR < 1 indicates a protective effect.