Anastomotic patterns of the facial parotid plexus (PP): A human cadaver study

Extratemporal Facial Nerve Interconnections and Trunk's Variability: A Systematic Review with Meta-Analysis

BACKGROUND

The present systematic review with meta-analysis is a significant contribution to the understanding of the morphological variability of the facial nerve (FN) extratemporal segment, i.e., the facial trunk (FT) variability, its division, and terminal branching patterns. The study also provides a comprehensive overview of the clinical significance of the FN extracranial division.

METHODS

Four online databases were utilized to conduct the systematic review according to evidence-based anatomy guidelines. A meta-analysis of the studies included was carried out using R programming software. The combined prevalence of the FN variants was calculated, along with subgroup and cumulative analysis.

RESULTS

From the systematic review, 29 studies were retrieved as eligible for our initial purpose. However, 19 studies followed the same classification system and were selected for the meta-analysis, with a total sample of 2453 nerves. The most common pattern of the FN morphology was the FT bifurcation (typical pattern), with a pooled prevalence of 94.1% and a single interconnection (IC) between the temporofacial and cervicofacial branches (23.1% pooled prevalence). Two ICs between these branches were the rarest pattern (8.9% pooled prevalence).

CONCLUSIONS

Our findings underscore the extensive morphological variability of the FN extratemporal anatomy, which has led to confusion among researchers. While several classification systems have been developed, none accurately represent the typical and variant anatomy. Our meta-analysis provided a small range between 8.9-23.1% for the rarest and most common pattern; thus, diversity is the rule. Therefore, it is not safe to conclude the typical morphology of FN extratemporal anatomy for its whole distribution before the FT's division (proximally) and its terminal branches (distally). Nevertheless, the bifurcation of the FT can be considered the typical morphology, and it is far more constant than the distal branching pattern. These findings have significant implications for surgical procedures, particularly parotidectomy, where surgeons must exercise utmost caution due to the potential clinical implications of FN injury.

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.

Anatomical knowledge of zygomatico-buccal plexus in a cadaveric study

The details of the facial nerve pattern were clearly explained in the parotid gland (PG), lateral area of the face, and periorbital areas to prevent the unexpected outcome of medical intervention. However, it remains unclear whether information about the zygomatico-buccal plexus (ZBP) in the masseteric and buccal regions. Therefore, this study aimed to help clinicians avoid this ZBP injury by predicting their common location. This study was conducted in forty-two hemifaces of twenty-nine embalmed cadavers by conventional dissection. The characteristics of the buccal branch (BB) and the ZBP were investigated in the mid-face region. The results presented that the BB gave 2-5 branches to emerge from the PG. According to the masseteric and buccal regions, the BB were arranged into ZBP in three patterns including an incomplete loop (11.9%), a single-loop (31.0%), and a multi-loop (57.1%). The mean distance and diameter of the medial line of the ZBP at the corner of the mouth level were 31.6 (6.7) and 1.5 (0.6) mm respectively, while at the alar base level were 22.5 (4.3) and 1.1 (0.6) mm respectively. Moreover, the angular nerve arose from the superior portion of the ZBP at the alar base level. The BB formed a multiloop mostly and showed a constant medial line of ZBP in an area approximately 30 mm lateral to the corner of the mouth, and 20 mm lateral to the alar base. Therefore, it is recommended that physicians should be very careful when performing facial rejuvenation in the mid-face region.

Extratemporal facial nerve branching patterns: systematic review of 1497 cases

Objective

The aim of this systematic review was to analyse the complex anatomy of the extratemporal portion of the facial nerve with an accurate description of the branching patterns based on the Davis classification.

Method

Medline, ScienceDirect and the Cochrane Library databases as well as other sources were searched by two independent reviewers.

Results

Analysis of 21 studies with a total of 1497 cases showed that type III is the most common branching pattern accounting for 26.8 per cent of cases. The type I pattern, previously considered as the normal anatomy in most textbooks, was the fourth most common branching pattern at 16.3 per cent. The majority of specimens (96.4 per cent) were found to have a bifurcated main trunk, and only 3.2 per cent were found with a trifurcated main trunk.

Conclusion

Surgeons should be aware of anatomical variations in the course of the facial nerve. An early identification of the branching pattern during surgery reduces the risk for iatrogenic facial nerve injury.

Nerve autofluorescence under near-ultraviolet light: cutting-edge technology for intra-operative neural tissue visualization in 17 patients

BACKGROUND

Nerve visualization and the identification of other neural tissues during surgery is crucial for numerous reasons, including the prevention of iatrogenic nerve and neural structure injury and facilitation of nerve repair. However, current methods of intra-operative nerve detection are generally expensive, unproven, and/or technically challenging. Recently, we have documented, in both in vivo animal models and ex vivo human tissue, that nerves autofluorescence when viewed in near-ultraviolet light (NUV). In this paper, we describe our use of nerve autofluorescence to facilitate the visualization of nerves and other neural tissues intra-operatively in 17 patients undergoing a range of surgical procedures.

METHODS

Employing the same prototype axon imaging system previously documented to markedly enhance nerve visualization in both in vivo animal and ex vivo human models, surgical fields were observed in 17 patients under both white and NUV light during parotid tumor resection (n = 3), thyroid tumor resection (n = 7), and surgery for peripheral nerve and spinal tumors and injury (n = 7).

RESULTS

In all 17 patients, the intra-operative use of the imaging system both was feasible and markedly enhanced the localization of all neural tissues throughout their course within the surgical field. All 17 procedures were successful and devoid of any peri-operative complications or post-operative neurological deficits.

CONCLUSIONS

Intra-operatively visualizing auto-fluorescent peripheral nerves and other neural tissues under NUV light is feasible in human patients across a range of clinical scenarios and appears to appreciably enhance nerve and other neural tissue visualization. Controlled studies to explore this technology further are needed.

Evaluation of the course of the marginal mandibular branch of the facial nerve: a fresh cadaveric study

The aim of this study was to determine the course of marginal mandibular nerve (MMN) in relation to the inferior border of the mandible from the gonion until its terminal insertion to the depressor anguli oris, relating the position to a palpable anatomical landmark with emphasis on the depth of the nerve in relation to platysma and the deep cervical fascia. Twelve fresh adult cadavers were dissected and the mandibular base was contoured using needles with 5mm gaps, starting from the mandibular angle to the muscular termination point of the nerve bilaterally. The distance between the MMN and the mandibular base and total length of the nerve was measured bilaterally. The highest levels of MMN were measured 6.9mm and 6.5mm above, and the lowest levels were measured 4mm and 3mm below the mandibular base on right and left sides, respectively. The mean (SD) total length of the nerve until the muscular termination point was calculated 33.57 (3.41) mm on the right and 33.51 (4.88) mm on the left side. Previous publications that we had read all fell short of defining the schematic pathway of the nerve, as the described landmarks were of a combination of bone and soft tissue, which are not always clinically reliable. We have overcome this difficulty by standardising the inferior border of the mandible as a point in order to trace the marginal mandibular branch pathway. It originates along the gonion and ends at the second premolar tooth area.

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.

MR Imaging of the Extracranial Facial Nerve with the CISS Sequence

BACKGROUND AND PURPOSE

MR imaging is not routinely used to image the extracranial facial nerve. The purpose of this study was to determine the extent to which this nerve can be visualized with a CISS sequence and to determine the feasibility of using that sequence for locating the nerve relative to tumor.

MATERIALS AND METHODS

Thirty-two facial nerves in 16 healthy subjects and 4 facial nerves in 4 subjects with parotid gland tumors were imaged with an axial CISS sequence protocol that included 0.8-mm isotropic voxels on a 3T MR imaging system with a 64-channel head/neck coil. Four observers independently segmented the 32 healthy subject nerves. Segmentations were compared by calculating average Hausdorff distance values and Dice similarity coefficients.

RESULTS

The primary bifurcation of the extracranial facial nerve into the superior temporofacial and inferior cervicofacial trunks was visible on all 128 segmentations. The mean of the average Hausdorff distances was 1.2 mm (range, 0.3-4.6 mm). Dice coefficients ranged from 0.40 to 0.82. The relative position of the facial nerve to the tumor could be inferred in all 4 tumor cases.

CONCLUSIONS

The facial nerve can be seen on CISS images from the stylomastoid foramen to the temporofacial and cervicofacial trunks, proximal to the parotid plexus. Use of a CISS protocol is feasible in the clinical setting to determine the location of the facial nerve relative to tumor.

Altered facial muscle innervation pattern in patients with postparetic facial synkinesis

OBJECTIVES/HYPOTHESIS

Using surface electrostimulation, we aimed to use facial nerve mapping (FNM) in healthy subjects and patients with postparetic facial synkinesis (PPFS) to define functional facial target regions that can be stimulated selectively.

STUDY DESIGN

Single-center prospective cohort study.

METHODS

FNM was performed bilaterally in 20 healthy subjects and 20 patients with PPFS. Single-pulse surface FNM started at the main trunk of the facial nerve and followed the peripheral branches in a distal direction. Stimulation started with 0.1 mA and increased in 0.1 mA increments. The procedure was simultaneously video recorded and evaluated offline.

RESULTS

A total of 1,873 spots were stimulated, and 1,875 facial movements were evaluated. The stimulation threshold was higher on the PPFS side (average = 9.8 ± 1.0 mA) compared to the contralateral side (4.1 ± 0.8 mA) for all stimulation sites or compared to healthy subjects (4.1 ± 0.5 mA; all P < .01). In healthy subjects, selective electrostimulation ± one unintended coactivation was possible at all sites in >80% of cases, with the exception of pulling up the corner of the mouth (65%-75%). On the PPFS side, stimulation was possible for puckering lips movements in 60%/75% (selective stimulation ± one coactivation, respectively), blinking in 55%/80%, pulling up the corner of the mouth in 50%/85%, brow raising in 5%/85, and raising the chin in 0%/35% of patients, respectively.

CONCLUSIONS

FNM mapping for surgical planning and selective electrostimulation of functional facial regions is possible even in patients with PPFS. FNM may be a tool for patient-specific evaluation and placement of electrodes to stimulate the correct nerve branches in future bionic devices (e.g., for a bionic eye blink).

LEVEL OF EVIDENCE

2b Laryngoscope, 130:E320-E326, 2020.

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.