The Impact of Preoperative Facial Nerve Weakness and Facial Nerve Outcomes in the Management of Patients With Parotid Metastases of Cutaneous Squamous Cell Carcinoma.

Background: Cutaneous squamous cell carcinomas (cSCC) metastasizing to the parotid gland can cause facial nerve (FN) dysfunction secondary to direct invasion, perineural spread, or surgical ablation. This study aims to characterize the prevalence of preoperative FN involvement in metastatic cSCC to the parotid and identify risk factors resulting in FN sacrifice.

Methods: Patients with parotid metastases from cSCC, treated surgically with parotidectomy with curative intent were identified through a retrospective cohort analysis of a prospectively maintained Sydney Head and Neck database from 1992 to 2021.

Results: Of 408 patients identified, 39 (10%) were found to have preoperative FN weakness, of which 41% underwent concurrent temporal bone resection compared to 9.1% for the overall cohort. All patients with preoperative FN weakness underwent FN sacrifice. FN sacrifice occurred in n = 145 (36%), of which 88 (61%) required sacrifice of a trunk or division. The 5-year disease free survival and disease specific survival was worse for patients requiring sacrifice of the FN trunk compared to no sacrifice, however there was no difference in survival for patients requiring sacrifice of the FN division or branch. We found those with > 23.5 mm parotid deposits had an odds ratio of 9.9 for FN sacrifice (95% CI 3.0-32.8, p < 0.001).

Conclusions: Preoperative FN weakness was present in 10% of patients and 36% had some part of the FN sacrificed. There was no significant difference in outcomes for patients with and without preoperative FN weakness. Patients who undergo sacrifice of the FN trunk have worse survival compared to those not requiring FN sacrifice, however similar outcomes were observed in those requiring lessor degrees of FN sacrifice. The likelihood FN sacrifice rises with increasing parotid deposit size.