Original Research—Head and Neck Surgery

Recurrent Pleomorphic Adenoma of the Parotid Gland: Intraoperative Facial Nerve Monitoring during Parotidectomy

Otolaryngology– Head and Neck Surgery 2014, Vol. 151(1) 87–91 Ó American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0194599814528098 http://otojournal.org

Huawei Liu, MD1, Weisheng Wen, PhD1, Haitao Huang, MD1, Yongqiang Liang, MD2, Xinying Tan, MD1, Sanxia Liu, MD1, Changkui Liu, MD1, and Min Hu, PhD1

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Received November 23, 2013; revised January 28, 2014; accepted February 25, 2014.

Abstract Objective. To determine the benefit to postoperative facial function of intraoperative facial nerve monitoring (IFNM) during recurrent pleomorphic adenoma (RPA) parotid surgery.

Introduction

Study Design. Cohort study with planned data collection. Setting. Chinese PLA General Hospital. Subjects and Methods. Fifty-eight RPA parotidectomies were performed between 2004 and 2012. Recurrence was confirmed by histopathologic examination. None of the patients had preoperative facial palsy. Electromyography-based IFNM was used in 28 patients; 30 patients were unmonitored. The durations of surgery and the severity of postoperative facial nerve palsy were compared between the 2 groups. Results. There were no significant differences between the 2 groups in the incidence of immediate or permanent facial paralysis after RPA parotidectomy (P = .95 and P = .36, respectively). However, the differences in the average duration of surgery and the severity of postoperative facial nerve palsy after total parotidectomy or wide resection were significant (P \.01 and P = .01, respectively). In contrast, these differences were not significant after superficial parotidectomies (P = .43 and P = .49, respectively). The average recovery time of temporary facial nerve paralysis was significantly shorter in the monitored group compared with the unmonitored group, independent of surgical technique (P \ .01). Conclusion. The use of IFNM during total or wide resection RPA parotidectomy reduced the duration of surgery and the incidence of postoperative facial paralysis and enhanced recovery. However, there was little impact on facial nerve outcomes when IFNM was used during superficial RPA parotidectomy. Keywords pleomorphic adenoma, parotid gland, recurrence, facial nerve, palsy, intraoperative monitoring

Pleomorphic adenoma is the most common neoplasm of the parotid gland. Although pleomorphic adenoma is considered a benign tumor, it has a relatively high rate of recurrence. Incidence rates have been reported between 4% and 45% and depend mainly on the initial type of surgical technique.1-3 Furthermore, the risk for facial nerve injury and the incidence of temporary and permanent postoperative facial palsy are increased after surgery for recurrent pleomorphic adenoma (RPA) of the parotid gland. This is primarily because previous dissection makes it difficult to distinguish between the facial nerve and scar tissue.4-6 Intraoperative facial nerve monitoring (IFNM) is a technique that has been used in parotid surgery for several years, with the aim of reducing the risk for facial nerve injury during parotid gland surgery. The use of IFNM during first-line surgery of the parotid gland remains controversial; whereas some researchers believe that IFNM can reduce operating times and the risk for facial nerve injury,7,8 others believe it has little impact on the outcome of postoperative facial nerve function.9 The number of reports on the use of IFNM in RPA surgery of the parotid gland is small. Makeieff et al10 conducted a study on the basis of 32 RPA patients who had undergone electromyography and demonstrated that IFNM could reduce operative time, decrease the incidence rate of permanent facial nerve paralysis, and shorten the recovery time of postoperative facial nerve function. The purposes of this study were to analyze postoperative facial function and surgical duration in patients with RPA of the parotid gland and to provide a clinical basis for the use of IFNM during RPA surgery. 1 2

Department of Stomatolagy, Chinese PLA General Hospital, Beijing, China College of Stomatology, Hebei United University, Tangshan, China

Corresponding Author: Min Hu, PhD, Chinese PLA General Hospital, Department of Stomatology, 100853, Beijing, China Email: [email protected]

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Table 1. The Clinical Characteristics of the Patients with Recurrent Pleomorphic Adenoma. Variable

Monitored Group

Unmonitored Group

All Patients

P .54y

Gender Male Female Mean 6 SD age, y Surgical technique Superficial parotidectomy Total parotidectomy/wide resection Histopathology Uninodular recurrence Multinodular recurrence

12 16 39.9 6 10.9

12 18 39.2 6 12.2

24 34 40.0 6 11.5

7 21

8 22

15 43

.82* .89y

.43y 8 20

9 21

17 41

*Student’s t test. y Chi-square test.

Methods Patient Selection and Characteristics A total of 67 patients with RPA of the parotid gland who had been referred to our department between 2004 and 2012 were initially selected for this study. All patients had undergone preoperative clinical examinations, ultrasonic detection, and computed tomographic or magnetic resonance imaging scans that had shown tumor recurrence. Exclusion criteria were preoperative facial nerve paralysis (6 patients), malignant transformation of RPA (3 patients), and radiation therapy (no patients). The remaining 58 patients were randomized before surgery. They had a mean age of 40.5 years (range, 19-63 years) and included 24 men and 34 women. Patients were divided into 2 groups; 28 were monitored (monitored group [MG]) and 30 were unmonitored (unmonitored group [UG]) during surgery. Patients’ clinical characteristics (gender, age, histopathology, and surgical technique) are presented in Table 1. Written informed consent was obtained from all eligible patients, and the study received ethical approval from the institutional review boards of the Chinese PLA General Hospital.

Surgical Procedures The choice of surgical technique depended on the initial surgical procedure, the extent of the operation, and the characteristics of the recurrent tumor. Superficial parotidectomy was performed if the previous operation had been enucleation or partial parotidectomy (7 in the MG, 8 in the UG). Total parotidectomy or wide resection was performed if the previous operation had involved superficial or total parotidectomy (21 in the MG, 22 in the UG). Histopathologic analysis was performed to identify single-node recurrence (8 in the MG, 9 in the UG) and multinodular recurrence (20 in the MG, 21 in the UG). All surgical procedures were performed under general anesthesia. For the MG, the NIM II Response nerve monitoring system (Medtronic, Minneapolis, Minnesota) was used. Four subdermal monopolar needle electrodes were placed in the frontalis, musculus orbicularis oculi, zygomatic minor, and

orbicularis oris to monitor electrical activity of the facial nerve during surgery. A subdermal ground electrode was placed into the shoulder tissue and manubrium sterni. The stimulation probe was used by the surgeon to identify the main trunk of the facial nerve when nerve localization was difficult. The current change of the direct electrical stimulation was 0.5 to 1.0 mA.

Postoperative Monitoring of Facial Nerve Function Patients were assessed for facial nerve palsy 7 days, 1 month, 3 months, 6 months, and 9 months after surgery. The analyses were carried out by an independent doctor, and grades were determined from photographs. Facial nerve function was defined according to the House-Brackmann (HB) facial nerve grading scale: grade 1 (no facial palsy) to grade 6 (complete palsy).

Statistical Analysis Statistical analysis was performed using SPSS version 13.0 (SPSS, Inc, Chicago, Illinois). A 2-tailed Student’s t test was used to compare the duration of surgery. Two-tailed Mann-Whitney U tests were used to compare the recovery period of temporary facial paralysis and the HB grading scale, as it was assumed that the data were not normally distributed. Chi-square tests were used to compare the clinical and pathologic characteristics of the patients and the incidence rates of postoperative complications. Data are expressed as mean 6 SD. Differences were considered significant at P \ .05.

Results Patient Characteristics and Postoperative Complications The analyses showed that there were no significant differences in the clinical and pathologic features between the 2 groups (P . .05; Table 1). Postoperative complications occurred in 13 patients in the MG and in 12 patients in the UG: 4 cases of poor wound healing (2 each in the MG and UG), 3 cases of postoperative salivary fistula (1 in the MG, 2 in the UG), 2

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Table 2. Duration of Surgery in Patients with Recurrent Pleomorphic Adenoma.a Surgical Technique Superficial parotidectomy Total parotidectomy/wide resection Total

Monitored Group

Unmonitored Group

All Patients

P

142.9 6 9.6 224.5 6 37.5 203.3 6 49.0

138.8 6 10.0 281.1 6 41.5 237.7 6 73.4

140.7 6 10.0 252.5 6 46.3 224.3 6 65.6

.43 \.01 .04

a

Data are expressed as mean 6 SD.

Table 3. Postoperative Facial Palsy One Week after Surgery (Superficial Parotidectomy or Total Parotidectomy/Wide Resection) According to House-Brackmann Grade.a Surgical Technique Monitored* Superficialy Total/widez Unmonitored* Superficialy Total/widez

Grade 1

Grade 2

Grade 3

Grade 4

Grade 5

Grade 6

Total

2 2 0 1 1 0

5 1 4 2 2 0

12 3 9 8 3 5

5 1 4 8 1 7

4 0 4 8 1 7

0 0 0 3 0 3

28 7 21 30 8 22

a Grade 1 = no facial palsy, grade 6 = complete palsy. *P = .01, yP = .49, and zP = .01 (monitored vs unmonitored group, Mann-Whitney U test).

cases of postoperative local pain and paresthesia (1 each in the MG and UG), and 16 cases of gustatory sweating syndrome (9 in the MG, 7 in the UG). The application of IFNM did not significantly increase the incidence of postoperative complications (P = 0.62).

Comparisons of Surgery Duration and Facial Nerve Function between the Two Groups Overall, the average duration of parotid surgery was significantly shorter in the MG compared with the UG (P = .04). The difference was not significant when superficial parotidectomy was performed (P = .43) but was significantly shorter when total parotidectomy or wide resection were performed (P \ .01). These data are presented in Table 2. Postoperative facial nerve function was defined according to the HB classification system. The overall incidence rate of facial nerve paralysis was 94.8% (55 of 58). In the MG, the incidence rates of immediate and permanent facial palsy were 92.9% (26 of 28) and 10.7% (3 of 28), respectively. In the UG, the incidence rates were 96.7% (29 of 30) and 23.3% (7 of 30), respectively. There was no significant difference in immediate or permanent facial palsy between the 2 groups (P = .95 and P = .36, respectively). The distributions of facial palsies according their HB grade were compared between the 2 groups 1 week after the operation. Facial paralysis in the MG was less severe than in the UG (P = .01). When superficial parotidectomy was performed, there was no significant difference in the grade distribution of immediate facial paralysis between the 2 groups (P = 0.49; Table 3). However, when total parotidectomy or wide resection was performed, facial paralysis

in the UG was significantly more severe than that in the MG (P = .01; Table 3).

Recovery of Facial Nerve Function Facial nerve recovery was assessed for both groups during the follow-up period. Recovery was classed as \3, 3 to 6, 6 to 9, or .9 months. Patients who still had facial paralysis 9 months after surgery were defined as having permanent facial paralysis, as there was only a remote possibility of recovery. The average recovery time in the MG was significantly less than in the UG (P \ .01; Table 4), suggesting that patients with temporary facial paralysis could recover more quickly if they underwent surgery with IFNM. Table 5 shows the surgical technique, the HB grading score, and the facial nerve branches for the patients with permanent facial paralysis.

Discussion RPA remains a major problem in head and neck surgery. RPA parotid surgery after previous superficial or total parotidectomy is more difficult if the parotid region and facial nerve have previously been dissected. The risk for facial nerve injury is significantly increased because of the presence of scar tissue and the adherence to the tumor.11 Therefore, reducing the incidence and severity of postoperative facial paralysis is a continuing concern for surgeons.12,13 Incidence rates of postoperative facial paralysis after initial parotid surgery are reported to be 9.1% to 64.0% for temporary facial paralysis and 0% to 3.9% for permanent facial paralysis.14,15 In contrast, the incidence rates are considerably higher after RPA parotid surgery and are reported to be 90% to 100% and 11.3% to 29.0% for temporary and

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Table 4. Length of the Recovery Period of Facial Paralysis in Each Group After Surgery. Group Monitored Unmonitored Total

\3 mo

3-6 mo

6-9 mo

.9 mo

Total

15 5 20

6 7 13

2 10 12

3 7 10

26 29 55

P \.01 (Mann-Whitney U test).

Table 5. Characteristics of Permanent Facial Paralysis After Surgery. Patient 1 2 3 4 5 6 7 8 9 10

Group Monitored Monitored Monitored Unmonitored Unmonitored Unmonitored Unmonitored Unmonitored Unmonitored Unmonitored

Type of Surgery

Branch Affected

Permanent Facial Nerve Function (House-Brackmann Grade)

Total Total Total Superficial Total Total Total Total Total Total

Marginal Marginal Total Marginal Marginal Buccal, marginal Temporary Buccal, marginal Total Total

2 3 5 2 2 4 3 3 5 5

permanent facial paralysis, respectively.6,11,16 In comparison, we found that the incidence rate of permanent facial paralysis in patients who were monitored during RPA parotidectomies was 10.7%, compared with 23.3% in the unmonitored group. However, the difference was not significant. To reduce bias caused by different types of operation, the patients were allocated to 2 groups on the basis of surgical procedure. In the superficial parotidectomy group, limited surgery (enucleation or partial parotidectomy), with little or no involvement of the branches of the facial nerve, had been performed previously. As such, the facial nerve adhesion was lighter, and the facial nerve was easier to identify. Conversely, in the total parotidectomy or wide resection group, the previous surgery had involved the main trunk and most of the facial nerve branches. As a consequence, the facial nerve was tightly adhered to the surrounding fibrous tissue and was difficult to identify, increasing the possibility of facial nerve injury. There are several potential benefits of using of IFNM during parotidectomy, including reducing the total operating time by aiding the surgeon in identifying the main trunk of the facial nerve when localization is difficult and providing real-time monitoring of intraoperative facial nerve function.7,17 After surgical dissection of the facial nerve, electrical stimulation with the probe allows the functional integrity of the nerve to be assessed, which can help predict postoperative facial nerve function. It has previously been demonstrated that facial nerve monitoring can reduce the risk for iatrogenic injury in middle ear and skull base surgery, and the use of IFNM in

parotid surgery can limit the rate of postoperative complications.18-20 Our findings were consistent with these reports. However, to avoid the possibility of false-negative reactions during the operation, the surgeon needs to have comprehensive knowledge of the anatomy combined with surgical experience.21 In recurrence surgery, unlike first-line surgery, the surgeon does not always try to reveal the nerve branches but instead attempts to preserve the fibrosis that surrounds the branches, which limits nerve exposure and mechanical manipulation.10 By avoiding devascularization and perineurium exposure, the surgeon can remove the recurrent tumor after identification of the nerve branches without revealing them. This strategy reduces surgical trauma caused by mechanical separation. This study has shown that the use of IFNM in total or wide resection RPA parotidectomy can shorten the duration of surgery, reduce the severity of facial nerve injury, shorten the recovery period of facial nerve paralysis, and provide an objective index for postoperative facial nerve evaluation. These benefits have been attributed to the ability of IFNM to identify the main trunk, thereby reducing mechanical injury of the facial nerve. However, the use of IFNM in our study failed to show a reduction in the incidence of facial paralysis. This may be due to the following reasons: although the use of IFNM can help reduce the risk for facial nerve injury, the incidence of facial nerve paralysis is affected by the size and extent of the recurrent tumor and the preceding surgical procedure,22 and the sample size in our study was small; therefore, future studies with larger sample sizes are required.

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We found that with superficial parotidectomy, the use of IFNM did not reduce the duration of RPA surgery or the severity of facial nerve paralysis. This suggests that IFNM may have little benefit in this group of patients. Furthermore, the use of anesthetics and muscle relaxation may block the transmission of facial neuromuscular electrophysiologic information and affect the sensitivity and accuracy of facial nerve monitoring.23

8.

9.

Conclusions We have demonstrated that the use of IFNM during total parotidectomy or wide resection of RPA can reduce the duration of surgery, the incidence of postoperative facial paralysis and improve facial outcome. However, the use of IFNM during superficial parotidectomy had little impact on these factors, and it is important to note that facial nerve monitoring cannot replace the anatomic knowledge and skills of the surgeon.

10.

11.

12.

Author Contributions Huawei Liu, performance of surgery, manuscript writing; Weisheng Wen, performance of surgery, data collection; Haitao Huang, performance of surgery, data collection; Yongqiang Liang, data analysis, manuscript revision; Xinying Tan, performance of surgery, data analysis; Sanxia Liu, manuscript revision, data analysis; Changkui Liu, follow-up, photograph collection; Min Hu, study design, performance of surgery.

13.

14.

Disclosures Competing interests: None.

15.

Sponsorships: None. Funding sources: Beijing Municipal Natural Science Foundation (13G30867), National Natural Science Foundation of China (30872898).

16.

17.

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Recurrent Pleomorphic Adenoma of the Parotid Gland: Intraoperative Facial Nerve Monitoring during Parotidectomy.

To determine the benefit to postoperative facial function of intraoperative facial nerve monitoring (IFNM) during recurrent pleomorphic adenoma (RPA) ...
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