The Role of Anatomical Location of Parotid Tumors in the Incidence of Post-Operative Facial Nerve Paresis

Special Article - Oral & Maxillofacial Surgery

Austin J Surg. 2017; 4(2): 1102.

The Role of Anatomical Location of Parotid Tumors in the Incidence of Post-Operative Facial Nerve Paresis

Hegab AF¹* and Amer Y²

¹Department of Oral & Maxillofacial Surgery, Al-Azhar University-Cairo, Egypt

²Department of General surgery, Al-Azhar University- Cairo, Egypt

*Corresponding author: Hegab AF, Department of Oral & Maxillofacial Surgery, Al-Azhar University in Cairo, Egypt

Received: June 16, 2017; Accepted: July 13, 2017; Published: July 20, 2017


Objective: The parotid part of the Facial nerve dividing the parotid gland into the superficial and deep lobe. This close relation of the facial nerve to the parotid gland making the facial nerve at high risk of injury during parotid gland surgery. The current study aimed to evaluate the diagnostic accuracy of CT for evaluation of the anatomical location of parotid tumors and its relation to the incidence of post-operative facial nerve paresis with antegrade dissection technique.

Methods: The study enrolled the patients undergoing surgical removal of parotid tumors. Preoperative evaluation of the tumor location within the parotid gland tumor was done using axial and coronal CT. The primary outcome factor was the tumor location within the parotid gland. While secondary outcome factors were patient age, tumor size. Results: Deep lobes, upper and anterior part tumors are associated with higher incidence of the TFND (P < 0.001, <0.0001, <0.0349, respectively). While, tumors located in the lower parts, posterior parts or the superficial lobe are showing lower incidence of TFND. With respect to tumor size, there was no significant association between the tumor size and incidence of facial nerve injury. The other clinical factors (age & sex) did not show a relation to the incidence of the TFND.

Conclusion: The tumor location is the most significance factor of postoperative TFND. The incidence of TFND is highly significant with tumors located in the upper parts, and/or anterior parts and/or deep lobe of the parotid gland.

Keywords: Parotidectomy; Facial nerve morbidity; Antegrade dissection technique


Surgical removal of the parotid tumor (Parotidectomy) was performed for the first time in 1832. Berard who removed parotid tumor of 8 years duration did the surgical procedure and introduced it into the world. Since then, a variety of modification has been proposed for treatment of benign and malignant parotid tumors [1].

Parotidectomy associated with a variety of postoperative complications including, Transient Facial Nerve Dysfunction (TFND), enduring facial nerve paralysis, salivary fistula, Frey’s syndrome, infection, and recurrence of the parotid tumor. Due to location of the parotid gland in the facial region, complications of the parotid gland surgery lead to disfigurement and can affect the quality of life [2].

Owing to the anatomical relation between the facial nerve and the parotid gland; the incidence of facial nerve injury is the most frequent complication after Parotidectomy. In the same time; facial never identification in the diagnostic image is extremely difficult. That is giving us two options. The first is direct identification of the nerve during surgery, which carry a risk of injury to the nerve. The second option is to use anatomical landmark in the imaging study to predict the location of the nerve to the tumor.

Facial nerve injury associated with Parotidectomy can results from different mechanisms include nerve detachment or cutting, stretching, nerve compression from heavy retraction and suture ligation, ligature entrapment, thermal and electrical injuries, and finally can result from ischemia [3]. Facial nerve trunk identification during Parotidectomy can be achieved by one of the following approaches, conventional antegrade dissection [4] of the facial nerve, and retrograde dissection [5].

Some prefer to identify the facial nerve trunk first and continue dissection forward through the course of the facial nerve branches which called the antegrade approach. The nerve trunk may prove difficult find in obese patients, those with large benign tumors or during procedures for recurrent pleomorphic adenomas where retrograde dissection of the nerve branches at the periphery may provide a useful alternative [6]. A number of publications have renewed focus on the retrograde technique [7-10].

Different factors can lead to facial nerve injury (either temporary or permanent) during Parotidectomy. The effect of type of the tumor (benign or malignant), the tumor size, age and sex are well-studied [11-13].

The purpose of the current study was to use different anatomical landmarks on the diagnostic image to predict the tumor location in relation to the facial nerve. Moreover, we study the possible predictive clinical and anatomical factors related to the occurrence of peripheral facial paralysis with antegrade dissection technique.

Patients and Methods

In order to explore the factors that play a role in the incidence of facial nerve injury following Parotidectomy, this study recruited patients who had been diagnosed with a parotid diseases that mandated a surgical intervention. The study enrolled the patients of the outpatient clinics of the department oral and maxillofacial surgery- faculty of dental medicine, department of general surgery faculty of medicine, Al-Azhar University hospitals in Cairo, Egypt, between the years 2014 and 2016. This study was approved by IRB and all participants signed an informed consent agreement according to the ethics of clinical research committee. After obtaining written patient consent, appropriate surgical procedures for the treatment of parotid tumors were performed. Type of the Parotidectomy was selected after careful clinical and radiographic evaluation to determine the nature of the parotid tumor and location.

Inclusion criteria: patients with parotid gland tumors required superficial Parotidectomy or total Parotidectomy. Patient with recurrent parotid tumor but without history of previous nerve palsy.

Patients fulfilling one or more of the following criteria were excluded from the study: patients with collagen diseases, history of facial nerve palsy, neuromuscular disorders affecting the face, diabetic neuropathy. The follow up period extended to 8 months for the cases with facial nerve palsy. And patients still under follow up for the evaluation of the recurrence of the parotid gland tumors.

The clinical examinations include examination of facial nerve function before surgery. The radiological investigations includes one or more of the following: neck Ultra Sound (US): as primary screening to detect whether the enlargement is superficial or deep lobe swelling, solid or cystic, and well defined or ill defined, and to detect enlarged Lymph Node (LNs). Fine needle aspiration biopsy was used to differentiate benign lesions from malignant one. Detailed evaluation of the tumor location within the parotid gland was done with CT. Moreover, CT was used for evaluation of the cervical LN and suspected metastasis.

Evaluation of the location of the tumor within the parotid gland was done by using three anatomical reference lines on the CT. The first line is the FN line: this line used for to determine whether the tumor was located in superficial or deep lobe; Facial Nerve (FN) line connects the lateral surface of the posterior belly of the digastrics muscle with the lateral surface of the cortex of the ascending mandibular ramus (Figure 1). If the tumor located anterior to this line will be considered as superficial lobe tumor. While tumor located behind the line will be considered as deep lobe tumor [14,15].