Landmarks of the facial nerve: implications for parotidectomy

Navigating the void: outcomes and adaptations during parotid surgery in the absence of posterior belly of digastric muscle

It is well known that the digastric posterior belly is one of the essential landmarks for facial nerve identification during parotid surgery. While there were multiple reports about variations of the digastric anterior belly, only a few anatomical variations of the posterior belly of the digastric muscle have been described.In this article, we describe an anatomical variation of the posterior belly of digastric muscle found during superficial parotidectomy of a patient with pleomorphic adenoma. This anatomical variation also led to an anatomical variation in the position of the facial nerve.To our knowledge, this is the first report of an absent posterior belly of digastric muscle found during live parotid surgery. The knowledge of current anatomical variation may help to avoid facial nerve injury during parotid surgery and preserve the function of muscles of facial expression.

Defining the Safe Entry Point in Deep Plane Facelifting with Novel Landmark for the Buccal Branch of the Facial Nerve

Background

In deep facial surgery, accurate preoperative landmarking of branches of the facial nerve is helpful in avoiding inadvertent facial nerve injury. The objective of our study was to determine the accuracy at which the intersection point of two bisecting lines that join facial surface landmarks can be used to accurately locate the buccal branch(es) of the facial nerve, specifically at the deep plane entry point (ie, intercept landmark).

Methods

Thirty-three cadavers were dissected to determine the position of the buccal rami relative to the intercept.

Results

Buccal rami crossed the intercept in 12.12% of specimens (0 mm from intercept, n = 4). Buccal rami passed superiorly in 66.67% of specimens (3.71 ± 3.28 mm from intercept, n = 7) and inferiorly in 21.21% of specimens (2.44 ± 0.92 mm from intercept, n = 7). Noteworthy, buccal rami were located within 1 cm of the intercept landmark with 96.97% accuracy (32/33 cadavers).

Conclusions

These data suggest that this novel intercept (1) reliably locates the buccal branch of the facial nerve as it courses distal to the parotid gland, and (2) helps define a "safe zone" for entry into the deep plane where the likelihood of encountering the facial nerve is extremely low.

Imaging of Facial Nerve With 3D-DESS-WE-MRI Before Parotidectomy: Impact on Surgical Outcomes

OBJECTIVE

The intra-parotid facial nerve (FN) can be visualized using three-dimensional double-echo steady-state water-excitation sequence magnetic resonance imaging (3D-DESS-WE-MRI). However, the clinical impact of FN imaging using 3D-DESS-WE-MRI before parotidectomy has not yet been explored. We compared the clinical outcomes of parotidectomy in patients with and without preoperative 3D-DESS-WE-MRI.

MATERIALS AND METHODS

This prospective, non-randomized, single-institution study included 296 adult patients who underwent parotidectomy for parotid tumors, excluding superficial and mobile tumors. Preoperative evaluation with 3D-DESS-WE-MRI was performed in 122 patients, and not performed in 174 patients. FN visibility and tumor location relative to FN on 3D-DESS-WE-MRI were evaluated in 120 patients. Rates of FN palsy (FNP) and operation times were compared between patients with and without 3D-DESS-WE-MRI; propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to adjust for surgical and tumor factors.

RESULTS

The main trunk, temporofacial branch, and cervicofacial branch of the intra-parotid FN were identified using 3D-DESS-WE-MRI in approximately 97.5% (117/120), 44.2% (53/120), and 25.0% (30/120) of cases, respectively. The tumor location relative to FN, as assessed on magnetic resonance imaging, concurred with surgical findings in 90.8% (109/120) of cases. Rates of temporary and permanent FNP did not vary between patients with and without 3D-DESS-WE-MRI according to PSM (odds ratio, 2.29 [95% confidence interval {CI} 0.64-8.25] and 2.02 [95% CI: 0.32-12.90], respectively) and IPTW (odds ratio, 1.76 [95% CI: 0.19-16.75] and 1.94 [95% CI: 0.20-18.49], respectively). Conversely, operation time for surgical identification of FN was significantly shorter with 3D-DESS-WE-MRI (median, 25 vs. 35 min for PSM and 25 vs. 30 min for IPTW, P < 0.001).

CONCLUSION

Preoperative FN imaging with 3D-DESS-WE-MRI facilitated anatomical identification of FN and its relationship to the tumor during parotidectomy. This modality reduced operation time for FN identification, but did not significantly affect postoperative FNP rates.

Retromandibular Vein, Digastric Muscle, and Greater Auricular Nerve in Superficial Parotidectomies for Patients with Pleomorphic Adenoma-A Surgical Experience

Retromandibular vein (RMV) and posterior belly of digastric muscle are among the landmarks used to identify facial nerve in parotid surgery. This observational cross-sectional study was done in the Department of ENT &HNS at a tertiary care teaching hospital for a period of 8 years with the aim to aware young otorhinolaryngologist about the relationship of posterior belly of digastric muscle & retromandibular vein with facial nerve and share our experience about preservation of posterior branch of greater auricular nerve. A total of 34 cases of superficial parotidectomies done for pleomorphic adenoma were included in this study. Relationship of facial nerve with retromandibular vein and posterior belly of digastric muscle was noted. Greater auricular nerve was identified, and every attempt was made to preserve its posterior branch. Retromandibular vein was medial to the trunks of facial nerve in 33 (97%) patients. It was lateral to lower division and medial to upper division in one case. Greater auricular nerve was seen to bifurcate into two branches (Anterior and posterior) in 21 (62%) cases while in one case(3%) three branches were seen emerging from main trunk and in another case(3%) first two branches were seen emerging and then anterior branch was further dividing into two. Preservation of posterior branch of greater auricular nerve was possible in 23 (68%) of patients. Posterior belly of digastric muscle was seen as a reliable and constant landmark. Facial nerve was seen superior to upper border of posterior belly of digastric muscle in all cases (100%). No anatomical variation of posterior belly was seen. Retromandibular vein is invariably seen medial to the trunks of facial nerve. Facial nerve is always seen superior to upper border of posterior belly of digastric muscle in almost all cases. Preservation of posterior branch of greater auricular nerve is possible in majority of the cases.

Simple Technique Using an Additional Landmark to Reliably Identify the Trunk of Facial Nerve During Parotidectomy: a Cadaveric and Clinical Correlation Study

The incidence of facial palsy in parotid surgeries is up to 50% transient and 17% complete facial palsy. Locating facial nerve trunk during parotid surgery can be tricky despite using the standard landmarks. During a cadaveric dissection, we came across a simple technique to identify the trunk of facial nerve which we have also tried to use it in clinical setting and found it to be useful. Parotidectomy was done in 12 cadaveric hemi-faces. The distance between the mastoid tip and the tympanic segment of facial nerve was measured. The distance of the facial nerve and mastoid tip and tympanomastoid suture and facial nerve was measured. The trunk of facial nerve was found to cross the tympanomastoid sulcus-mastoid tip at around 8-10 mm from the mastoid tip in 70% of the cases. We extrapolated this information in 5 cases of parotidectomy in operative setting. We were able to identify facial nerve trunk accurately in 4/5 cases. Imaginary line connecting the mastoid tip and tympanomastoid suture can be used to locate the probable position of the facial nerve trunk reliably during parotidectomy.

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

OBJECTIVE

This study was performed to report and analyze the prevalence of permanent facial nerve paralysis following parotidectomy for various benign and malignant lesions in a single center.

METHODS

This single-center retrospective study included all patients who underwent parotidectomy (total and superficial) for benign and malignant tumors and chronic inflammatory diseases during a 6-year period. Patients who had previously undergone an operation of the parotid gland and those with preoperative facial weakness were excluded.

RESULTS

The study included 127 patients ranging in age from 14 to 83 years (median, 45.89 years). Most patients were female (n = 83, 65.4%). The most prevalent procedure was superficial parotidectomy (n = 117, 92.1%), followed by total parotidectomy (n = 6, 4.7%). The average operative duration was 138 minutes (range, 80-400 minutes). Histopathology revealed that 109 (85.8%) patients had benign tumors, 14 (11.0%) had malignant tumors, and 4 (3.1%) had chronic sialadenitis. Only two patients sustained an injury to the cervical branch of the facial nerve.

CONCLUSION

In this single-center experience of parotid surgery, the rates of transient and permanent facial paralysis were acceptably low at 9.0% and 1.6%, respectively, for all pathologies.

Facial nerve: A review of the anatomical, surgical landmarks and its iatrogenic injuries

Facial nerve iatrogenic injuries are serious and can negatively affect the quality of life of the patients. Due to the properties of the nerve, the complications are devastating involving the aesthetic appearance and the function of the face. Moreover, the multiple branches of the nerve increase the risk of an iatrogenic injury making the detailed knowledge of the anatomical correlations around them critical. In this review, a meticulous analysis was performed including the surgical procedures posing the greater risk of an iatrogenic injury as well as the full description of all the reported anatomical landmarks involving the extracranial course of the facial nerve.

Do Benign Mass Lesions in the Superficial Lobe of Parotid Gland Influence Landmark-Based Search for Facial Nerve Trunk At Surgery?

Objective

To assess the influence of benign mass lesions in the superficial lobe of parotid on the known anatomic landmarks for identifying the facial nerve trunk.

Method

Patients with unilateral biopsy-proven benign mass lesions in the superficial parotid were selected for this observational study. During superficial/partial superficial parotidectomy, distance of the facial nerve trunk from each landmark was assessed using spring calliper and correlated with the lesion’s volume (measured from the pre-operative imaging). At least two identifiers among tragal pointer (TP), posterior belly of digastric muscle (PBDM) and tympanomastoid suture (TMS) were considered.

Results

The study involved 32 patients. The lesions mostly involved the parotid tail (50%) and pretragal region (34.3%), and constituted of pleomorphic adenoma (~66%) and Warthin’s tumor (~9%), the rest being various cysts and hamartomas. TP was universally uncovered, while PBDM and TMS were exposed in 26 and 25 patients, respectively. Average distances between the facial nerve trunk and TP, PBDM and TMS were 12.79 mm (SD=2.33), 9.78 mm (SD=1.21) and 7.58 mm (SD=1.33), respectively. Correlation coefficients between the lesion’s volume and the distance of facial nerve from a given landmark were -0.11, 0.04 and -0.16 for TP, PBDM and TMS, respectively.

Conclusion

TP was the most easily available landmark on surgical dissection, while PBDM was the most consistent and the least variable when volumetric data of the benign mass lesions in the superficial lobe of parotid were considered as a factor influencing the distance from the facial nerve trunk.

New classification of branching pattern of facial nerve during parotidectomy: A cross sectional study

Background

Parotidectomy is one of the most frequent modes to treate tumors of parotid gland. Previous studies documented a variation in the facial nerve branching which might risk facial nerve injury during Parotidectomy.

Aim of study

To make a new classification system that includes a new branching pattern of facial nerve trunk that has not been described before, also to mention a simple method of how to identify the facial nerve trunk, all that will help the new surgeon in performing parotidectomy with less complications and unpredictable outcome.

Methods

A prospective cross sectional study on 460 patients underwent partial or total parotidectomy for different pathologies were enrolled during the period January 2004 till September 2020. Three investigations were considered; the anatomy of the facial nerve trunk (FNT), exact site of facial nerve trunk in relation to fixed landmarks, finally we observed any communications between the branches. We made a new classification based mainly on the anatomical variations in the branching pattern of the FNT; namely, types (I, II and III). Each type subdivided according to the length of facial nerve trunk and also according to the communication between the branches.

Results

Type I reported in majority of cases; 78.26%. type II (15.2%) which is the newly discovered branching pattern, and type III (6.6%). Total FNT length was 1–10 mm in more than half (54.35%) of cases. In 64.35% of cases FNT was in the midpoint between the tragal pointer (TP) and tip of mastoid's process (TMP). In 50 (10.87%) of the cases there was anastomotic connection between the buccal and mandibular branches, and in 20(4.34%) the communication was always a loop between the upper and lower divisions of FNT.

Conclusion

There is a profound variation in the facial nerve branching pattern that has not been previously reported. Awareness about differences in the anatomy of the facial nerve assisted useful information to surgeon to preserve FN during parotidectomies.

•

Previous studies documents variation in the facial nerve branching which might risk FN injury during parotidectomy.

•

A new classification system is made that includes a new branching pattern of FN trunk that has not been described before.

•

a simple method of how to identify the facial nerve trunk.

•

All that will help the new surgeon in performing parotidectomy with less complications and unpredictable outcome.

Endoscope-Assisted Surgery of the Elongated Styloid Process Using the Retroauricular Approach: An Anatomic Study for Clinical Application

PURPOSE

Surgical shortening of the styloid process (SP) mainly involves intraoral and transcervical approaches. A retroauricular incision was performed by our surgical team in endoscope-assisted shortening of the SP. This study aimed to clarify the important anatomic landmarks and adjacent structures around the SP through a retroauricular approach.

METHODS

Fifteen fresh corpses (30 sides) were dissected via a retroauricular approach, and indexes were measured.

RESULTS

The great auricular nerve (GAN) was divided into the anterior ear branch, lobe branch, and posterior ear branch. The distance from the branch of the GAN to the root of the ear lobe was 21.96 ± 2.55 mm. In the space around the SP, the vertical distance from the junction of the diabetic posterior belly and the mastoid tip to the SP was found to be 12.29 ± 2.46 mm, with a total distance between the skin in front of the mastoid and the facial nerve of 21.63 ± 3.27 mm. The distance between the facial nerve across the SP and the root of the SP was 11.93 ± 2.32 mm.

CONCLUSIONS

The retroauricular incision starts from the level of the notch between the tragus and extends backward in an arc to avoid injury to the retroauricular branch of the GAN. The posterior fascia of the parotid gland and the leading edge of the sternocleidomastoid muscle, posterior belly of the digastric muscle, and styloid hyoid muscle are regarded as landmarks for the SP.

A new landmark for the identification of the facial nerve during parotid surgery: A cadaver study

OBJECTIVE

Precise knowledge of facial nerve anatomy is crucial for parotid surgery. Although several surgical landmarks to identify the facial nerve have been described in literature, their position is variable, inconsistent, and difficult to follow in some cases. The purpose of this study was to prove that the facial nerve trunk (FNT) is located midway between the mastoid tip (MT) and osteocartilaginous junction of the external auditory canal (EAC).

METHODS

A prospective study of 7 frozen cadaver specimens, of which 13 facial sides were dissected. The distances between the osteocartilaginous junction and the MT, between the FNT and the MT, and between the FNT and the osteocartilaginous junction were recorded, respectively.

RESULTS

The distance between the osteocartilaginous junction and the MT ranged from 17 to 21 mm, with a mean of 19.5 mm (SD = ±1.19). The mean distances between the osteocartilaginous junction and the FNT and between the MT and the FNT were 9.2 mm (±1.58) and 10.3 mm (±1.79), respectively.

CONCLUSION

The FNT was consistently located close to the midpoint between mastoid tip inferiorly and bony-cartilaginous junction of the EAC superiorly.

LEVEL OF EVIDENCE

NA.

Incidence of postoperative facial weakness in parotid tumor surgery: a tumor subsite analysis of 794 parotidectomies

Background

The reported incidence of facial weakness immediately after parotid tumor surgery ranges from 14 to 65%. The purpose of this study was to evaluate the incidence of postoperative facial weakness related to parotidectomy with use of preoperative computed tomography (CT), intraoperative facial nerve monitoring, and surgical magnification. Also, we sought to elucidate additional information about risk factors for postoperative facial weakness in parotid tumor surgery, particularly focusing on the tumor subsites.

Methods

We retrospectively reviewed 794 cases with parotidectomy for benign and malignant tumors arising from the parotid gland (2009–2016). Patients with pretreatment facial palsy were excluded from the analyses. Tumor subsites were stratified based on their anatomical relations to the facial nerve as superficial, deep, or both. Multivariable logistic regression analyses were conducted to identify risk factors for postoperative facial weakness.

Results

The overall incidences of temporary and permanent (more than 6 months) facial weakness were 9.2 and 5.2% in our series utilizing preoperative CT, intraoperative facial nerve monitoring, and surgical magnification. Multivariable analysis revealed that old age, malignancy, and recurrent tumors (revision surgery) were common independent risk factors for both temporary and permanent postoperative facial weakness. In addition, tumor subsite (tumors involving superficial and deep lobe) was associated with postoperative facial weakness, but not tumor size. Extent of surgery was strongly correlated with tumor pathology (malignant tumors) and tumor subsite (tumors involving deep lobe).

Conclusion

Aside from risk factors for facial weakness in parotid tumor surgery such as old age, malignant, or recurrent tumors, the location of tumors was found to be related to postoperative facial weakness. This study result may provide background data in a future prospective study and up-to-date information for patient counseling.

Variations in Facial Nerve Branches and Anatomical Landmarks for Its Trunk Identification: A Pilot Cadaveric Study in the Lithuanian Population

Objective The purpose of this study was to evaluate facial nerve (FN) branching variations based on Davis and Kopuz classifications in the Lithuanian population and measure the shortest distance from the facial nerve trunk (FNT) to its anatomical landmarks. Methods Twenty-two hemifaces of 11 cadavers were dissected. The preauricular skin cut was made and extended behind the ear lobe and along the inferior border of the mandible. The skin with subcutaneous tissue and superficial fascia were separated and medially retracted, and the parotid gland was dissected anterogradely. The FNT and its furcation type and branching pattern were disclosed and noted based on Davis and Kopuz classifications. Further, the shortest distance from the FNT to the anatomical landmarks of the tragal pointer (TP), the angle of mandible (AM), and the tip of mastoid process (TMP) was measured. Results The prevalence of branching patterns did not differ significantly compared to Davis classification. Based on Kopuz, type IVA pattern was the most common in six cases (27%). Eighteen (82%) trunks split as bifurcations and two (9%) trifurcations, while two (9%) had separate double trunks. The shortest distance (mm) from the FNT to the TP is 9.30 ± 0.93, AM 36.45 ± 4.14, and TMP 12.52 ± 2.30. Conclusion The prevalence of FN variations in the Lithuanian population is similar to Davis classification. The AM and TMP are consistent superficial bony landmarks for trunk identification, while the distance from the TP highly varies among studies. Surgeons should be aware of double FNT during parotidectomy, which is described in Kopuz classification.

The Role of the Parotid-Mastoid Fascia in Identification of the Facial Nerve Trunk During Parotidectomy

OBJECTIVE

We aim to describe the parotid fascia as a landmark that can help identify the immediately underlying facial nerve trunk.

METHODS

Dissection of the parotid fascia and identification of the facial nerve trunk were carried out on 8 fresh cadaveric parotid glands. The attachments and arrangement of the parotid gland and its fascia were evaluated and histologically assessed, with special attention to the fascia overlying the facial nerve trunk.

RESULTS

The parotid fascia envelops the posterior aspect of the parotid gland in an open-book fashion. Posteriorly, it connects to the anterior and medial aspect of the mastoid tip. Posterosuperiorly, it attaches to the inferior aspect of the tragal pointer. Directly medial to the fascia lies the facial nerve trunk.

CONCLUSION

The parotid fascia, particularly the parotid-mastoid segment overlying the facial nerve trunk, can be utilized as an additional landmark of depth to help identify the facial nerve trunk during a parotidectomy in conjunction with other commonly used standard anatomic landmarks. The parotid fascia sling spans from the mastoid and tragal pointer to the parotid gland and can be easily palpated intraoperatively. Once the fascia is removed, the facial nerve trunk is identified.

A new method for tracing the facial nerve trunk using the posterior auricular nerve

Tracing the facial nerve trunk is an essential action in parotid surgery, because of the implications of injury to the nerve or its branches. More than a few landmarks that may help the surgeon in this task have been proposed (e.g., the posterior belly of the digastric muscle, the tragal pointer, among others), under the assumption that additional access methods improve the surgical technique and reduce the possibility of harmful post-operative consequences. Here we present evidence that the posterior auricular nerve may be used to trace the facial nerve trunk. We dissected 75 cadaveric heminecks, exposed the auricularis posterior muscle and adnexa, and attempted to follow the posterior auricular nerve to the facial nerve trunk. The auricularis posterior muscle, nerve, and artery were identified in all heminecks, securing an anatomically reliable route to the facial nerve trunk. Average length of the nerve from the auricularis posterior muscle to the facial nerve trunk was 28 mm (±6.2 mm). The angle between the posterior auricular nerve and the vertical segment of the FN trunk was 39.5° (±7.7°). We conclude that the posterior auricular nerve may be used as a landmark to trace the facial nerve trunk. It is advantageous due to the relatively simple and consistent regional anatomy, and also because manipulation of this nerve does not present a risk given that the auricularis posterior muscle is vestigial. The proposed landmark is particularly important in revision surgery, where the pre-auricular anatomy may have been distorted and scarred by previous operations. Clin. Anat. 32:453-457, 2019. © 2019 Wiley Periodicals, Inc.

Variation of the Great Auricular Nerve and Prediction of the Facial Nerve Trunk Size

Supplemental Digital Content is available in the text.

Background:

This study aimed to reveal the anatomical variation in the great auricular nerve (GAN) and the correlation between the size of the GAN and the facial nerve trunk (FNT), so as to aid surgeons to perform safe facelift surgery and parotidectomy.

Methods:

Sixteen human cadavers were studied on 16 left and 15 right facial sides. The GAN’s branching patterns, location, and the mean width of the GAN and FNT were measured.

Results:

The average distance where the nerve emerged from under the sternocleidomastoid muscle was 87.61 ± 12.13 mm when measured perpendicular to the Frankfort horizontal plane. The branching pattern of the GAN could be classified into 5 types of which the most common was type 3 (30.77%), where the GAN divided into the anterior (superficial) and posterior branches, and then the deep branch originated from the posterior branch of the GAN. The mean width of the GAN and FNT from all the dissections was 3.26 ± 0.67 mm and 3.36 ± 0.71 mm, respectively. There was a significant correlation between the width of the nerves on both facial sides (right: r =0.740, P =0.002; left: r = 0.839, P < 0.001).

Conclusions:

This study revealed the anatomical variation and the width of the GAN, which can strongly predict the width of the FNT. This should be taken into consideration during facelift surgery and parotidectomy, especially in patients with a small GAN to prevent iatrogenic injury to the small FNT.

Fetal anatomy of the facial nerve trunk and its relationship with posterior auricular artery

PURPOSE

The aims of the study are to define anatomy of the facial nerve (FN) and its main trunks as well as their relationship with the posterior auricular artery in fetal period to evaluate the data for regional surgery in newborns and young infants.

METHODS

Formalin-fixed 34 fetuses from anatomy laboratory collection with a mean gestational age of 26.4 ± 4.6 (20-36) weeks were dissected. Parameters regarding the presence of major or minor trunks, width, length, branching pattern of FN were evaluated according to side, gender and trimester. The positional relationship of posterior auricular artery with the FN trunk was inspected.

RESULTS

On all sides only the major trunk of the FN was detected. For length and width parameters, there was no statistically significant difference for side and gender except for trimester. Linear functions were found as 0.329 + 0.025 × weeks for width and 5.264 + 0.185 × weeks for length. There are statistically significant linear relationships between width and length of the FN trunk and week parameters as r = 0.507, p < 0.001 and r = 0.484, p < 0.001, respectively. Posterior auricular artery crossed FN trunk laterally in 42 of 53 sides, medially in 9 sides while it was puncturing it proximally in 2 sides. In all cases, it was in close contact to the FN trunk. FN trunk showed bifurcation in 82% and trifurcation in 18%.

CONCLUSION

Dimensions of FN trunk, growth ratio and linear functions can be beneficial in understanding the fetal growth of FN trunk and its usage for grafts. Data about the relationship of the posterior auricular artery with FN trunk may be crucial in avoiding iatrogenic injuries during surgery in early ages.

Borle's triangle: A reliable anatomical landmark for ease of identification of facial nerve trunk during parotidectomy

Purpose

An accurate understanding of the anatomy, identification and preservation of facial nerve is critical in performing successful functional parotidectomies. The current literature is replete with inconsistencies of various landmarks when used alone for identification of facial nerve trunk (FNT). The purpose of the paper is to introduce a new anatomical triangle, Borle's triangle (BT) for safer and reliable operative identification of FNT during parotodectomies.

Patients and methods

Between Aug 2014 and Dec 2017, twelve patients who reported with unilateral disease of the parotid gland with intact facial nerve function who underwent superficial or complete parotidecomies were included in the study. BT was conceptualized by intersection of three imaginary lines drawn along anatomical structures and forming a triangle comprising of angles a, b and c.

Results

Introperatively, BT helped reliably identify the FNT and its branches successfully in all the cases. The mean distance of FNT from angle b was found to be 12.18 ± 1.7 mm. Transient neurological deficits with one or more branches were seen in four cases whilst, one case had transient deficit with all the five peripheral branches. All of them spontaneously resolved completely by the end of three months post operatively.

Conclusions

When used in isolation, substantial variations exist in distances measured from anatomic landmarks to the main FNT in the literature. The BT utilizes three commonly used anatomical landmarks. It predictably helps in proper anatomic orientation, identification and preservation of FNT and branches with ease in parotidectomies.

Anatomy of the facial nerve branching patterns, the marginal mandibular branch and its extraparotid ramification in relation to the lateral palpebral line

Background: Surgery of face and parotid gland may cause injury to branches of the facial nerve, which results in paralysis of muscles of facial expression. Knowledge of branching patterns of the facial nerve and reliable landmarks of the surrounding structures are essential to avoid this complication. Objective: Determine the facial nerve branching patterns, the course of the marginal mandibular branch (MMB), and the extraparotid ramification in relation to the lateral palpebral line (LPL). Materials and methods: One hundred cadaveric half-heads were dissected for determining the facial nerve branching patterns according to the presence of anastomosis between branches. The course of the MMB was followed until it entered the depressor anguli oris in 49 specimens. The vertical distance from the mandibular angle to this branch was measured. The horizontal distance from the LPL to the otobasion superious (LPL-OBS) and the apex of the parotid gland (LPL-AP) were measured in 52 specimens. Results: The branching patterns of the facial nerve were categorized into six types. The least common (1%) was type I (absent of anastomosis), while type V, the complex pattern was the most common (29%). Symmetrical branching pattern occurred in 30% of cases. The MMB was coursing below the lower border of the mandible in 57% of cases. The mean vertical distance was 0.91±0.22 cm. The mean horizontal distances of LPL-OBS and LPLAP were 7.24±0.6 cm and 3.95±0.96 cm, respectively. The LPL-AP length was 54.5±11.4% of LPL-OBS. Conclusion: More complex branching pattern of the facial nerve was found in this population and symmetrical branching pattern occurred less of ten. The MMB coursed below the lower border of the angle of mandible with a mean vertical distance of one centimeter. The extraparotid ramification of the facial nerve was located in the area between the apex of the parotid gland and the LPL.

Surgical Landmarks to Locating the Main Trunk of the Facial Nerve in Parotid Surgery: A Systematic Review

PURPOSE

The purpose of this study was to describe distances from commonly used anatomic landmarks to the main trunk of the facial nerve during parotid surgery.

MATERIALS AND METHODS

A systematic search of the published literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies from January 1, 1990 to January 1, 2017 that measured distances to the main trunk of the facial nerve from common anatomic landmarks were eligible. Inclusion criteria were English-language articles with distances measured from the main trunk of the facial nerve to anatomic landmarks. The primary outcome variable was the distance from the respective anatomic landmarks. Other variables included surgical approach, year, and existential status of subject (cadaveric or living).

RESULTS

The search yielded 1,412 studies (1,397 by PubMed, 15 by reference searching), with 10 studies meeting the inclusion criteria. Within the 10 studies, there were 30 reported means and 375 dissected cadavers. The most common incision was the standard preauricular incision; the mean distances to the facial trunk from landmarks were 13.6 ± 11.0 mm (n = 6 reported means) for the tragal pointer, 8.79 ± 3.99 mm (n = 7 reported means) for the posterior belly of the digastric muscle, 10.5 ± 1.4 mm (n = 4 reported means) for the tip of the mastoid process, 14.99 ± 1.68 mm (n = 3 means) for the transverse process of C1, 3.79 ± 2.92 mm (n = 6 means) for the tympanomastoid fissure, 9.80 ± 0 mm (n = 1 mean) for the styloid process, and 11.77 ± 1.42 mm (n = 3 means) for the external auditory meatus. Formal assessment of inter-study variability could not be assessed because of the small number of studies and measurements.

CONCLUSION

There are substantial variations in measurements from anatomic landmarks to the main trunk of the facial nerve in the literature. Therefore, multiple landmarks can be used to identify the main trunk of the facial nerve during parotid surgery. The distances reported in this study can guide surgeons during parotid surgery to decrease the risk of facial nerve damage.

Useful Method for Intraoperative Monitoring of Facial Nerve in a Scarred Bed

Facial nerve is the main cranial nerve for the innervation of facial expression muscles. Main trunk of facial nerve passes approximately 1 to 2 cm deep to tragal pointer. In some patients, where a patient has multiple operations, fibrosis due to previous operations may change the natural anatomy and direction of the branches of facial nerve. A 22-year-old male patient had 2 operations for mandibular reconstruction after gunshot wound. During the second operation, there was a possible injury to the marginal mandibular nerve and a nerve stimulator was used intraoperatively to monitor the nerve at the tragal pointer because the excitability of the distal segments remains intact for 24 to 48 hours after nerve injuries. Thus, using a nerve stimulator at the operational site may lead to false-positive muscle movements in case of injuries. Using the nerve stimulator to stimulate the main trunk at the tragal point may help to distinguish the presence of possible injuries. A reliable method for intraoperative facial nerve monitoring in a scarred operational site was introduced in this letter.

Bifid Facial Nerve Trunk: Anatomic and Surgical Considerations

The segment of the facial nerve (FN) between its emergence from the skull through the stylomastoid foramen and its bifurcation at the parotid area is referred to as the FN trunk (FNT). Injury to the facial nerve trunk is among the most undesirable outcomes following different otologic, plastic, maxillofacial, and neurosurgical procedures. These procedures frequently involve manipulation and isolation of this segment, and meticulous dissection should be practiced to avoid iatrogenic damage to the nerve. Identification and exposure of the FN trunk, however, may be difficult because it is surrounded by dense connective tissue. This dissection becomes even more difficult and risky when the normal anatomy is distorted.During a routine left conservative superficial parotidectomy of a Pleomorphic Adenoma in the superficial lobe of the left parotid gland, duplication of the FNT was encountered. The FNT after its exit through the stylomastoid foramen, split into 2 main divisions, which rejoined before its penetration into the parotid gland. To the best of our knowledge, this variation has not been previously reported.

The Relationship of the Facial Nerve to the Condylar Process: A Cadaveric Study with Implications for Open Reduction Internal Fixation

Introduction. The mandibular condyle is the most common site of mandibular fracture. Surgical treatment of condylar fractures by open reduction and internal fixation (ORIF) demands direct visualization of the fracture. This project aimed to investigate the anatomic relationship of the tragus to the facial nerve and condylar process. Materials and Methods. Twelve fresh hemicadavers heads were used. An extended retromandibular/preauricular approach was utilized, with the incision being based parallel to the posterior edge of the ramus. Measurements were obtained from the tragus to the facial nerve and condylar process. Results. The temporozygomatic division of the facial nerve was encountered during each approach, crossing the mandible at the condylar neck. The mean tissue depth separating the facial nerve from the condylar neck was 5.5 mm (range: 3.5 mm–7 mm, SD 1.2 mm). The upper division of the facial nerve crossed the posterior border of the condylar process on average 2.31 cm (SD 0.10 cm) anterior to the tragus. Conclusions. This study suggests that the temporozygomatic division of the facial nerve will be encountered in most approaches to the condylar process. As visualization of the relationship of the facial nerve to condyle is often limited, recognition that, on average, 5.5 mm of tissue separates condylar process from nerve should help reduce the incidence of facial nerve injury during this procedure.

Use of scopolamine patches in patients treated with parotidectomy

The antimuscarinic effect of scopolamine causes a reduction of salivary secretion, so it can be used successfully in postoperative parotid surgery. The aim of this article was to demonstrate the efficiency of postoperative use of scopolamine transdermal patch in reduction of complications due to the presence of saliva in the surgical spaces.

Easy and Safe Method for Facial Nerve Identification in Parotid Surgery

Background A safe and easy anatomical landmark is proposed to identify the facial nerve in parotid surgery. The facial nerve forms the center point between the base of the styloid process and the origin of the posterior belly of the digastric muscle. Objective To evaluate the consistency, accuracy, and safety of the landmark in identifying the facial nerve. Methods The study was designed in three steps: a cadaver study, a radiologic study, and a prospective clinical study. Anatomy was initially studied in two cadavers. Then the images of 200 temporal styloid regions were studied for consistency of the presence of the styloid base. In the second part of the radiologic study, the distance between the styloid base and the origin of the posterior belly of the digastric muscle was studied in 50 parotid regions. The clinical study involved 25 patients who underwent parotidectomy. Results The styloid base was present in all the images studied. The mean distance between the styloid base and the origin of the posterior belly of the digastric was found to be 0.72 cm (range: 0.45-0.99 cm). The facial nerve could be identified consistently and safely in all patients. Conclusion This trident landmark provided safe, accurate, and easy identification of the facial nerve using two fixed bony landmarks.

Morphological study of the occipital belly of the occipitofrontalis muscle and its innervation

PURPOSE

Occipital belly (OB) of occipitofrontalis muscle (epicranius) is a muscle which covers the occipital part of the skull. The posterior auricular nerve (PAN) is the first extracranial branch of the facial nerve, which supplies the OB. The PAN is one of the structures used to identify the facial nerve during surgeries such as parotidectomy and mastoidectomy. In the present report, we provide detailed anatomical knowledge of the OB and its innervation.

METHODS

Twenty-six hemifaces from 14 Korean cadavers were dissected. The mastoid tip, external occipital protuberance (EOP), a horizontal line that is parallel to the Frankfurt horizontal plane (x-axis), and a vertical line through the EOP (y-axis) were used as reference points and lines.

RESULTS

The OB demonstrated a variety of features and was mostly asymmetrical. The muscle bellies were observed to angle toward the temporoparietalis muscle laterally, with the aponeurosis angled at approximately 55°-65°. The mean width and height were 60.9 ± 8.7 and 31.7 ± 7.5 mm, respectively. Muscle bellies were located at a mean distance of 7.1 ± 2.5 mm superior to the x-axis and 29.6 ± 6.4 mm lateral to the y-axis. The mean vertical distance from the origin of the PAN at the anterior border of the mastoid process (MP) to the mastoid tip was 6.1 ± 2.1 mm. The mean nerve angle between the PAN and the x-axis was 55.7° ± 6.8°. The entry point of the PAN that innervates the OB was positioned at a mean distance of 9.0 ± 3.5 mm superior to the x-axis and 79.0 ± 8.1 mm lateral to the y-axis.

CONCLUSIONS

Understanding the morphometrical characteristics of the OB and its innervation may potentially improve surgical outcomes to assist in locating the posterior auricular branch of the facial nerve.

Use of steroids for facial nerve paralysis after parotidectomy: A systematic review

AIM: To systematically review the literature to assess the efficacy of corticosteroids in treating post-parotidectomy facial nerve palsy (FNP).

METHODS: We searched the Cochrane library, EMBASE and MEDLINE (from inception to 2014) for studies assessing the use of corticosteroids in post-parotidectomy FNP. Studies were assessed for inclusion and quality. Data was extracted from included studies.

RESULTS: Two randomised controlled trials met the inclusion criteria. One study assessed the use of dexamethasone and the other prednisolone. None of the studies demonstrated a significant difference in the outcome of FNP post-parotidectomy with the use of corticosteroids vs no therapy. The majority of FNP post-parotidectomy is transient. Preoperative factors (size of tumour and malignancy), intraoperative factors (extent of parotidectomy and integrity of facial nerve at the end of the operation) are important in determining prognosis of FNP if it does occur.

CONCLUSION: Corticosteroids do not appear to improve FNP prognosis post-parotidectomy. Further studies assessing patients by cohort and with long term follow-up are required to increase scientific evidence.

Identification of facial nerve during parotidectomy: a combined anatomical & surgical study

To find out the most easily identifiable and anatomically consistent landmark for identification of facial nerve during parotid surgery. Ten cadaveric dissections and ten live parotid surgeries for different types of parotid tumours were done. Cadaveric dissection was performed in the Department of Anatomy and the surgeries were done in the Department of ENT and Head and Neck surgery of R. G. Kar Medical College of Kolkata. The distance of the facial nerve trunk from three most commonly used landmarks (viz., tympanomastoid suture, tragal pointer and posterior belly of digastric muscle) was measured in both cadaver and live patients. The ease of identification of the nerve trunk using each of the landmarks, particularly during live surgery was also assessed. The mean distance of the tympanomastoid suture from the facial nerve trunk was 3.5 mm (cadaver) and 3.87 mm (live surgery), the tragal pointer was found to be at a mean distance of 16.61 mm (cadaver) and 16.36 mm (live surgery) and in case of the posterior belly of digastric muscle it was 7.41 mm (cadaver) and 8.03 mm (live surgery). During live surgery the posterior belly of digastric was found to be the most easily identifiable landmark with a consistent anatomical relationship with the nerve trunk. The posterior belly of digastric muscle is the most easily identifiable and a very consistent landmark for facial nerve dissection during parotidectomy. When supplemented with the tragal pointer, accuracy in identifying the facial nerve trunk is very high, thereby avoiding inadvertent injury to the nerve trunk.

Utilization of the tympanomastoid fissure for intraoperative identification of the facial nerve: a cadaver study

PURPOSE

Intraoperative identification of the facial nerve is an essential component of parotid gland surgery. Failure to visualize the facial nerve during the procedure can result in significant complications such as facial palsy. Several anatomic landmarks are used clinically to identify the facial nerve trunk; however, most of these structures have variable locations with respect to the nerve. The tympanomastoid fissure is the closest and least variable of the anatomic landmarks used in parotid gland surgery. The aim of this study was to evaluate the distance between the tympanomastoid fissure and the facial nerve trunk.

MATERIALS AND METHODS

Thirty cadaver sides were dissected. A modified Blair incision exposed the facial nerve trunk, and the dissection was extended to the stylomastoid foramen and adjacent mastoid process. The distance between the most lateral aspect of the tympanomastoid fissure and facial nerve trunk was obtained using a digital caliper.

RESULTS

The distance from the tympanomastoid fissure to the facial nerve trunk ranged from 3.3 to 9.2 mm with a mean of 4.9 mm.

CONCLUSIONS

The results showed that the tympanomastoid fissure is a close and predictable anatomic landmark that can be used to identify the facial nerve trunk intraoperatively.

Anomalous location of facial nerve deep to parotid gland

The knowledge of normal and variant anatomy of the facial nerve is essential for safe surgery of the parotid gland. The location of a parotid mass in relation to the course of the facial nerve determines whether superficial or total parotidectomies should be performed. The variant course of the facial nerve within the parotid may endanger the nerve during parotid surgeries. The present report is an attempt to help the surgeons to minimize the error that can damage the nerve without previous knowledge of such type of rare variation.

Double facial nerve trunk emerged from the stylomastoid foramen and petrotympanic fissure: a case report

There are several studies concerning branches of the facial nerve, but we encountered less information about the trunk of the facial nerve in the literature. During the routine dissection of a 65-yr-old Caucasian male cadaver, double facial nerve trunk emerged from the stylomastoid foramen and petrotympanic fissure were encountered. Because of an extremely rare variation, we presented this case report. In addition this cadaver had two buccal plexuses. These plexuses and other branches were formed to structures like to polygon. These anatomic peculiarities were described, photographed and illustrated. Finally, magnetic resonance imaging was performed by using 1.5T scanner to this cadaver. The facial nerve trunk can be damaged during surgical procedures of the parotid gland tumours and submandibular region. Surgeons who are willing to operate on this area should be aware of the possible anatomical variations of the facial nerve trunk.

Superficial parotidectomy versus retrograde partial superficial parotidectomy in treating benign salivary gland tumor (pleomorphic adenoma)

PURPOSE

Of all benign salivary gland tumors of the parotid gland, pleomorphic adenoma (mixed tumor) is the most common. It accounts for 60% to 70% of all benign tumors of the parotid gland. This neoplasm arises in patients in the fourth to sixth decade of life, with a female predominance. The surgical excision of this lesion continues to be the subject of major debate. The goal is to avoid facial disability yet attain complete resection without perforation of the capsule/pseudocapsule. The purpose of our study is to compare 2 surgical techniques performed at the Ear, Nose, and Throat and Maxillofacial Departments, Rambam Medical Center, Haifa, Israel, and determine which is preferable in treating this lesion.

PATIENTS AND METHODS

We reviewed 48 patients who underwent excision of pleomorphic adenoma of the parotid gland between 1996 and 2005 at Rambam Medical Center: 18 were treated surgically with the classical superficial parotidectomy (SP) technique, using an anterograde approach, and 30 were treated with retrograde partial superficial parotidectomy (PSP). We compared the 2 surgical techniques in terms of surgical time, histopathologic size of the lesion, amount of excised healthy parotid tissue, histologic margin, and the preservation of the capsule/pseudocapsule. We also made clinical records of temporary or definitive injury to the facial nerve, which branches of the facial nerve were temporarily or definitively injured, the occurrence of Frey syndrome, esthetic satisfaction, and the amount of recurrence or infection after surgery.

RESULTS

Of the 48 patients, 19 (39.6%) were male and 29 (60.4%) were female, with a mean age (+/- SD) of 43.8 +/- 16.97 years (median, 50 years; range, 12-79 years). We found a significant difference (P = .029) in mean surgical time (+/- SD): 171 +/- 49.7 minutes (median, 165 minutes) when performing the classical SP and 145 +/- 42.7 minutes (median, 130 minutes) when performing the retrograde PSP. Much more healthy parotid tissue was taken out with the classical procedure (mean, 51.4 +/- 13.6 mm; median, 50 mm) than with the retrograde PSP technique (mean, 39.2 +/- 11.8; median, 35 mm) (P = .01). There was a significant difference (P = .0003) in facial nerve injuries: 39% of patients did not report any facial deficit in the SP group compared with 90% in the PSP group. In the SP group, only 3 patients reported a permanent deficit, and in the PSP group, only 3 patients had a temporary deficit (compared with 8 in the SP group). The main injuries occurred in the mandibular branch with both techniques: 6 SP and 2 PSP. There was no difference in esthetic satisfaction: 72.2% of patients in the SP group and 80% in the PSP group had no esthetic complaints. In the SP group, patients mainly complained about swelling (3 patients), and in the retrograde PSP group, the main complaint was depression (4 patients). Frey syndrome was found in 9 patients in the retrograde PSP group and 4 in the classical SP group (with an overall rate of 27.7%). The lesion recurred in only 2 patients--1 in each group.

CONCLUSION

With both of the techniques, we found satisfactory results. In the majority of cases, retrograde PSP is a superior technique to the classical SP, although Frey syndrome is more often observed with the former.

Is the high submandibular transmasseteric approach to the mandibular condyle safe for the inferior buccal branch?

PURPOSE

There are basically 3 main approaches for extra-articular mandibular condyle fractures: low cervical, retromandibular and preauricular. These include a risk of facial palsy affecting the marginal mandibular branch. We use a high submandibular transmasseteric approach featuring masseter section 10-20 mm above the mandibular basilar edge. Our null hypothesis was that both the marginal mandibular and the inferior buccal branches are not more at risk than in other surgical approaches.

METHODS

This study was based on 20 parotidomasseteric dissections from 10 embalmed cadaveric heads. We used as reference the vertical line, passing through the mandibular angle, parallel to the preauricular line. We performed measurements of the marginal mandibular and inferior buccal branches' heights.

RESULTS

The inferior buccal branch had an average height of 16.8 mm and the highest standard deviation (7.2). Extremes were, respectively, 32 and 7 mm. The marginal mandibular branch had an average height of 3.2 mm with standard deviation equal to 3.0. Extremes were, respectively, 9 and -3 mm.

CONCLUSION

The high submandibular transmasseteric approach provides great exposure of facial nerve branches lying on the masseter muscle, if even encountered. Through masseteric incision performed between 10 and 20 mm above the basilar edge of the mandible, the marginal mandibular branch is safe from wound with an added safety margin of 4 mm. The surgeon using this approach is most likely to encounter the inferior buccal branch. It can then be avoided under visual control. This makes it a swift and safe approach to the mandibular condyle.

The precision of four commonly used surgical landmarks for locating the facial nerve in anterograde parotidectomy in humans

In addition to using intra-operative facial nerve monitoring in helping to locate the position of the facial nerve in anterograde parotidectomy, numerous soft tissue and bony landmarks have been proposed to assist the surgeon in the early identification of this nerve. There is still dispute within the literature as to the most effective method, if any, of locating the nerve. The purpose of this study was to measure the distance (in twenty-six embalmed cadavers) from four of the most commonly used surgical landmarks to the main trunk of the facial nerve-the posterior belly of digastric muscle (PBDM), the tragal pointer (TP), the junction between the bony and cartilaginous ear canal (EAM) and the tympanomastoid suture (TMS). The main trunk of the facial nerve was found 5.5+/-2.1mm from the PBDM, 6.9+/-1.8 mm from the TP, 10.9+/-1.7 mm from the EAM and 2.5+/-0.4 mm from the TMS. From this, the TMS can be used as a reliable indicator for locating the main trunk of the facial nerve. In addition, this study also demonstrated a statistically significant difference between the sexes in relation to the two bony landmarks used here, the EAM and the TMS, with the facial nerve found further away from those landmarks in females compared to males. With the advent of 3D construction and reformatting of images, these values may come to the forefront in pre-operative planning for locating the facial nerve in anterograde parotidectomy.