Pattern of facial nerve palsy during parotidectomy: a single-center experience

MR-Neurography of the facial nerve in parotid tumors: intra-parotid nerve visualization and surgical correlation

PURPOSE

One of the most severe complications in surgery of parotid tumors is facial palsy. Imaging of the intra-parotid facial nerve is challenging due to small dimensions. Our aim was to assess, in patients with parotid tumors, the ability of high-resolution 3D double-echo steady-state sequence with water excitation (DE3D-WE) (1) to visualize the extracranial facial nerve and its tracts, (2) to evaluate their relationship to the parotid lesion and (3) to compare MRI and surgical findings.

METHODS

A retrospective study was conducted including all patients with parotid tumors, who underwent MRI from April 2022 to December 2023. Two radiologists independently reviewed DE3D-WE images, assessing quality of visualization of the facial nerve bilaterally and localizing the nerve's divisions in relation to the tumor. MRI data were compared with surgical findings.

RESULTS

Forty consecutive patients were included (M:F = 22:18; mean age 56.3 ± 17.4 years). DE3D-WE could excellently visualize the nerve main trunk and the temporofacial division in all cases. The cervicofacial branch was visible in 99% of cases and visibility was good. Distal divisions were displayed in 34% of cases with a higher visibility on the tumor side (p < 0.05). Interrater agreement was high (weighted kappa 0.94 ± 0.01 [95% CI 0.92-0.97]). Compared to surgery accuracy of MRI in localizing the nerve was 100% for the main trunk, 96% for the temporofacial and 89% for the cervicofacial branches.

CONCLUSIONS

Facial nerve MR-neurography represents a reliable tool. DE3D-WE can play an important role in surgical planning of patients with parotid tumors, reducing the risk of nerve injury.

Intraoperative Facial Nerve Involvement in Parotid Tumours - A Retrospective Analysis in a Tertiary Care Centre

Purpose

The study aims to provide a comprehensive overview of the various malignant and benign parotid tumours and evaluate the predictive factors for intraoperative nerve involvement leading to facial palsy (FP).

Methods

It is a single-centre retrospective analysis for reviewing the involvement of facial nerve in post- parotidectomy patients. The clinical database from January 2012 to December 2020 was included in the study with a follow-up period of a minimum of 2 years. To maintain homogeneity, all squamous cell carcinomas of level 2 nodes involving parotid or residual/recurrent disease of the oral cavity requiring parotid dissection were excluded.

Results

A total of 248 patients (171 benign; 77 malignant) were evaluated with a mean age of 46.48 ± 10.76 years. The presence of malignancy increases the risk of FP (p = 0.027). 37 (14.92%) patients with FP were detected which included 34 with partial [32.35% in malignant; 62.16% in recurrent pleomorphic adenoma (RPA)] and 3 with total paralysis (66.67% in malignant; 33.33% in RPA). The recurrence of pleomorphic adenoma increases FP. While old age, larger size, hard fixed swelling with masseteric space (MS) infiltration appeared as risk factors for FP in malignant tumours (p = 0.047; p = 0.004; p < 0.00001 respectively).

Conclusion

Tumour size, malignancy, hard fixed mass, masseteric space infiltration, recurrence, and age > 45yrs have been statistically significant predictive factors for intraoperative facial nerve involvement leading to FP. The study also revealed that FP occurred more commonly when there was concurrent involvement of both superficial and deep lobes but was not statistically significant.

Acute Onset of Delayed Facial Nerve Paralysis After an Uncomplicated Total Parotidectomy for an Oncocytoma

Facial nerve injury is one of the most substantial potential sequelae of parotid surgery. Pulling, stretching, and otherwise disturbing the facial nerve during parotid surgery can lead to post-surgical neural paresis and consequential deficits in facial movement. Furthermore, transection of the main facial nerve trunk or its branches, either purposeful or incidental, can lead to complete paralysis of the related facial musculature. Facial nerve injury is often diagnosed immediately post-operatively as evident by deficits in ipsilateral facial motion on examination of the patient in the recovery unit or, at most, by one week post-operatively. Although delayed onset facial nerve paralysis is seen in traumatic injury and otologic surgery, it is uncommon that facial nerve paralysis presents late after parotid surgery in the absence of hematoma development, viral reactivation, or secondary insult. Here, we present the case of a 70-year-old man developing a delayed acute onset of hemi-facial paralysis 12 days after right-sided total parotidectomy for an oncocytoma; a facial nerve examination done immediately post-operatively and at the one-week post-operative follow-up was found to be normal. The patient was treated with two courses of high-dose oral steroids with close-to-complete resolution.

Proposals for Standardization of Intraoperative Facial Nerve Monitoring during Parotid Surgery

Intraoperative facial nerve monitoring (FNM) has been widely accepted as an adjunct during parotid surgery to facilitate identification of the facial nerve (FN) main trunk, dissection of FN branches, confirmation of FN function integrity, detection of FN injury and prognostication of facial expression after tumor resection. Although the use of FNM in parotidectomy is increasing, little uniformity exists in its application from the literature. Thus, not only are the results of many studies difficult to compare but the value of FNM technology is also limited. The article reviews the current literature and proposes our standardized FNM procedures during parotid surgery, such as standards in FNM setup, standards in general anesthesia, standards in FNM procedures and application of stimulus currents, interpretation of electrophysiologic signals and prediction of the facial expression outcome and pre-/post-operative assessment of facial expressions. We hope that the FNM standardized procedures will provide greater uniformity, improve the quality of applications and contribute to future research.