Branching patterns of the facial nerve and its communication with the auriculotemporal nerve

This study examines the anatomic relationships and variability of the facial nerve trunk and its branches, with emphasis on the intraparotid connections between the divisions. Microdissections were performed on 30 Korean half-heads, and the facial nerve trunks and branches were exposed. The average depth of the stylomastoid foramen from the skin surface was 21.0±3.1 mm, and the distance between the stylomastoid foramen and the bifurcation of the temporofacial (upper) and cervicofacial (lower) divisions was 13.0±2.8 mm. In 26 of 30 dissections (86.7%), the facial nerve trunk bifurcated into two main divisions, and a trifurcation pattern was seen in the other four cases (13.3%). According to the origin of the buccal branches, we classified the branching patterns of the facial nerve into four categories. In type I (13.8% of cases), the buccal branches arose from the two main divisions of the trunk but not from other branches of the facial nerve. In type II (44.8% of cases), the buccal branches arising from the two main divisions were interconnected with the zygomatic branch. In type III (17.3% of cases), the marginal mandibular branch sent nerve twigs to the buccal branch, which originated from the upper and lower divisions. In type IV (17.3% of cases), the nerve twigs from the zygomatic and marginal mandibular branches merged to the buccal branch arising from the two main divisions. Communications between the facial and auriculotemporal nerve branches, which are known as communicating auriculotemporal nerves, were observed in 28 of the 30 cases (93.3%). Familiarity with these common variations in the facial anatomy provides useful information for the surgeon in careful dissection, preservation of the facial nerve, and complete removal of the tumors in parotidectomies.     

Anatomical study of the variations in innervation of the orbicularis oculi by the facial nerve

While the divisions of the facial nerve in the face are well known, the innervation of the orbicularis oculi by the different distal branches of the facial nerve is poorly described. To determine which branches of the facial nerve play a role in this innervation, the facial nerve was dissected in 30 fresh cadavers. The innervation of this muscle was in the form of two plexuses, a superior one, most often (93%) formed by the union of the temporal and superior zygomatic branches, and an inferior one, usually formed (63%) by the union of the inferior zygomatic and superior buccal branches. This new mode of innervation explains how, without damage to both plexuses, innervation of orbicularis oculi by the facial nerve remains functional. It also explains the often unsatisfactory results of treatment of primary blepharospasm, and the unusual character of palsies of this muscle in cervicofacial lifts.     

面神经颞、颧、颊支与SMAS关系的解剖学研究

目的 明确面神经颞支、颧支、颊支的走行及其与SMAS的关系,为面中部除皱术提供形态学资料.方法 10具(20侧)成人头部标本,逐层解剖观测,数据描记于以眼外眦点与耳屏上切迹点连线所在水平面为X轴(横坐标),耳屏上切迹点为原点建立的坐标系上.结果 ①面神经颞支以3支型为多,各支由腮腺上缘出腮腺,而后向前上越过颧弓中外1...     

Peripheral facial nerve communications and their clinical implications

The facial nerve (CN VII) nerve follows a torturous and complex path from its emergence at the pontomedullary junction to its various destinations. It exhibits a highly variable and complicated branching pattern and forms communications with several other cranial nerves. The facial nerve forms most of these neural intercommunications with branches of all three divisions of the trigeminal nerve (CN V), including branches of the auriculotemporal, buccal, mental, lingual, infraorbital, zygomatic, and ophthalmic nerves. Furthermore, CN VII also communicates with branches of the vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), and vagus nerve (CN X) as well as with branches of the cervical plexus such as the great auricular, greater, and lesser occipital, and transverse cervical nerves. This review intends to explore the many communications between the facial nerve and other nerves along its course from the brainstem to its peripheral branches on the human face. Such connections may have importance during clinical examination and surgical procedures of the facial nerve. Knowledge of the anatomy of these neural connections may be particularly important in facial reconstructive surgery, neck dissection, and various nerve transfer procedures as well as for understanding the pathophysiology of various cranial, skull base, and neck disorders.     

Anatomical study of the zygomatic and buccal branches of the facial nerve: Application to facial reanimation procedures

The facial nerve is responsible for any facial expression channeling human emotions. Facial paralysis causes asymmetry, lagophthalmus, oral incontinence, and social limitations. Facial dynamics may be re‐established with cross‐face‐nerve‐grafts (CFNG). Our aim was to reappraise the zygomaticobuccal branch system relevant for facial reanimation surgery with respect to anastomoses and crossings. Dissection was performed on 106 facial halves of 53 fresh frozen cadavers. Study endpoints were quantity and relative thickness of branches, correlation to “Zuker's point”, interconnection patterns and crossings. Level I and level II branches were classified as relevant for CFNG. Anastomoses and fusion patterns were assessed in both levels. The zygomatic branch showed 2.98 ± 0.86 (range 2–5) twigs at level II and the buccal branch 3.45 ± 0.96 (range 2–5), respectively. In the zygomatic system a single dominant branch was present in 50%, two co‐dominant branches in 9% and three in 1%. In 66% of cases a single dominant buccal twig, two co‐dominant in 12.6%, and three in 1% of cases were detected. The most inferior zygomatic branch was the most dominant branch (P = 0.003). Using Zuker's point, a facial nerve branch was found within 5 mm in all facial halves. Fusions were detected in 80% of specimens. Two different types of fusion patterns could be identified. Undercrossing of branches was found in 24% at levels I and II. Our study describes facial nerve branch systems relevant for facial reanimation surgery in a three‐dimensional relationship of branches to each other. Clin. Anat. 32:480–488, 2019. © 2019 Wiley Periodicals, Inc.     

The nerve supply of zygomaticus major: Variability and distinguishing zygomatic from buccal facial nerve branches

The zygomaticus major (ZM) is important for the human smile. There are conflicting data about whether the zygomatic or buccal branches of the facial nerve are responsible for its motor innervation. The literature provides no precise distinction of the transition zone between these two branch systems. In this study, a definition to distinguish the facial nerve branches at the level of the body of the zygoma is proposed. In the light of this definition, we conducted an anatomical study to determine how the source of innervation of the ZM was distributed. A total of 96 fresh‐frozen cadaveric facial halves were dissected under loupe magnification. A hemiparotidectomy was followed by antegrade microsurgical dissection. Any branch topographically lying superficial to the zygoma or touching it was classed as zygomatic, and any neighboring inferior branch was considered buccal. The arborization of the facial nerve was diffuse in all cases. In 64 out of 96 specimens (67%, 95% CI: 56% to 76%), zygomatic branches innervated the ZM. Buccal branches innervated ZM in the other 32 facial halves (33%, 95% CI: 24% to 44%). There were no differences in respect of sex or facial side. All facial halves displayed additional branches, which crossed the muscle on its inner surface without supplying it. In 31 specimens, a nerve branch ran superficial to ZM in its cranial third. According to our classification, the zygomaticus major is innervated by zygomatic branches in 67% of cases and by buccal branches in 33%. Clin. Anat. 31:560–565, 2018. © 2018 Wiley Periodicals, Inc.     

Anatomic landmarks of the buccal branches of the facial nerve

The aim of this study was to classify the buccal branches of the facial nerve in relation to the parotid duct and its relevance to surgical procedures such as rhytidectomy and parotid gland surgery. In this study, 30 cadaver heads (60 specimens) were dissected. The vertical and horizontal relationships between the buccal branches of the facial nerve and tragus, and parotid duct were recorded and analyzed. The buccal branches of the facial nerve were classified into four types: Type I: a single buccal branch of the facial nerve at the point of emergence from the parotid gland and inferior to the parotid duct. Type II: a single buccal branch of the facial nerve at the point of emergence from the parotid gland and superior to the parotid duct. Type III: buccal and other branches of the facial nerve formed a plexus. Type IV: two branches of buccal branch; one superior and one inferior to the duct at the point of emergence from the parotid gland. The buccal branches of the facial nerve are very vulnerable to surgical injury because of its location in the midface. For this reason, the surgeons who are willing to operate on this area should have a true knowledge about the anatomy of these branches.     

面神经分支的表盘定位及临床意义

目的：研究面神经分支的行程和分布及在外科手术中的意义。方法：用表盘在15个（30侧）人头部标本上进行面神经各分支的定位观察。结果：面神经各分支在表盘中位置较固定。左颞支位于11～12点间13例（86．7％），右支10例（66．7％）。左颧支位于10～11点间10例（66．7％），右支9例（60％）。左上颊支位于9～10点间12例（80％），右支14例（93％）。左下颊支位于8～9点间13例（86．7％），右支11例（73％）。左右下颌缘支位于6～7点间各有15例（100％）。结论：利用表盘对面神经各分支进行定位更具有可预见性，其结果对腮腺咬肌区解剖和外科手术寻找面神经分支具有参考价值。     

Extracranial Course of the Facial Nerve Revisited

Introduction : The extrapetrous course of the facial nerve has been a matter of study and debate since XIX century. Two different classifications have been classically proposed and widely accepted by most of the authors. Nevertheless, there are reported cases which do not fit in any of those. The aim of this study is to propose a new and useful classification. Material and methods : We have used 23 embalmed Caucasian adult cadavers (11 male and 12 female) belonging to the Bodies Donation and Dissecting Rooms Centre of the University Complutense of Madrid. The extra-petrous facial nerve was dissected in the possible specimens resulting in 38 facial nerves. The studied parameters were length, diameter of divisions, terminal branches, and nerve connections. Results : In every specimen two main divisions were found, temporofacial and cervicofacial. They divided into five terminal branches from cranial to caudal: temporal, zygomatic, buccal, marginal or mandibular, and cervical. Based on the comparison with previous proposed classifications, we have unified the patterns in 12 types being the most frequent types the type 3 (eight cases, 21.05%), with connections between temporal, zygomatic and buccal branches and the type 8 (eight cases, 21.05%), a complex network between temporal, zygomatic, buccal, and mandibular branches. The number of terminal branches was so variable. Conclusion : We propose a new 12-patterned classification which summarizes the previous ones. However, we consider that a good study of the number of terminal branches, connections between branches or with other cranial nerves are more useful for surgeons to avoid injuries to the facial nerve during surgery than complex classifications. Anat Rec, 302:599–608, 2019. © 2018 Wiley Periodicals, Inc.     

面神经颊支的应用解剖

目的：观测分析面神经颊支的分支类型及其与腮腺管之间的解剖关系，为腮腺区手术提供解剖学基础。方法：60例成人头部标本，观测面神经颊支的分支类型、行程、神经与腮腺管的位置关系。结果：面神经颊支以双干型多见(58．3％)，三干型次之(28．3％)。神经多行于腮腺管浅面(73．3％)。腮腺管走行在颊支之问的占61．7％，导管距上颊支垂直距离约4．86mm；腮腺管走行在神经下方者占11．7％，距下颊支的垂直距离约1．71mm；腮腺管走行在神经上方者占26．7％，距上颊支的垂直距离约2．56mm。结论：面神经颊支多行于腮腺管浅层，与腮腺管关系十分密切，腮腺区手术时循颊支向后追踪面神经是比较安全、有效的方法，容易掌握。     

面神经颞支的应用解剖

目的确定面神经颞支的数量、走行和分布情况,为涉及面侧区和颞区的美容外科手术提供解剖学资料。方法解剖33具(66侧)成人尸体标本,探明颞支支数及走行;测量面神经颞支各分支越过颧弓下缘、外眦角等部位的距离。结果面神经颞支有4个分支,分别称为颞支Ⅰ、Ⅱ、Ⅲ、Ⅳ。除颞支Ⅳ经腮腺前缘浅出外,其余均经上缘浅出。浅出后它们立即到达颧弓浅面,其中颞支Ⅰ主要发支到达额肌深面;颞支Ⅱ主要到达额肌与眼轮匝肌交界部深面。颞支Ⅲ、Ⅳ主要发支到达眼轮匝肌深面。测量得到面神经颞支各分支越过颧弓下缘处距外眦角的距离男性分别为3.8cm、3.5cm、2.9cm、和2.8cm;女性分别为3.6cm、3.3cm、2.7cm、2.6cm。面神经颞支各分支发出部位距颧弓下缘的距离男性分别为3.0cm、3.8cm、4.0cm、4.2cm;女性分别为2.7cm、3.3cm、3.3cm、3.7cm。结论面神经颞支根据性别具有基本确定的走行及分布,为相关的美容外科手术提供了解剖学依据。     

Neuroanastomosis and the innervation territory of the mental nerve

The aim of this study was to clarify the distribution pattern and innervation territory of the mental nerve (MN) in the skin and mucosa by topographic examination by Sihler's staining, thereby providing reference anatomical information for surgical procedures and to enable prediction of regions of sensory disturbance following nerve damage. Ten human specimens were subjected to Sihler's staining, which is a highly accurate method for visualizing the distribution of nerve fibers without altering their topography. Each branch of the MN overlapped adjacent branches (five cases), or else they were distributed individually at the lower lip (five cases). The MN anastomosed with some branches of the facial nerve near the mental foramen. Moreover, some branches of the MN anastomosed with the buccal nerve of the trigeminal nerve, which supplies sensation to the skin and mucosa over the lateral region of the lower lip (six cases). The details of the distribution pattern and innervations territory of the MN presented herein may enable the prediction of a region of sensory disturbance following MN damage. Moreover, knowledge of the pattern of synapses with adjacent branches of other nerves, such as the facial (marginal mandibular and cervical branches) and the buccal nerves, might help to improve our understanding around incomplete anesthesia during the surgical procedures in oral & maxillofacial region. Clin. Anat. 598–602, 2014. © 2013 Wiley Periodicals, Inc.     

The consistent presence of the human accessory deep peroneal nerve

Twenty-four human legs were dissected macroscopically to study the morphological details of the accessory deep peroneal nerve. This nerve arose from the superficial peroneal nerve and descended in the lateral compartment of the leg, deep to peroneus longus along the posterior border of peroneus brevis. Approaching the ankle joint, this nerve passed through the peroneal tunnels to wind around the lateral malleolus; it then crossed beneath the peroneus brevis tendon anteriorly to reach the dorsum of the foot. The accessory deep peroneal nerve was found in every case examined and constantly gave off muscular branches to peroneus brevis and sensory branches to the ankle region. In addition, this nerve occasionally had muscular branches to peroneus longus and extensor digitorum brevis, and sensory branches to the fibula and the foot. The anomalous muscles around the lateral malleolus were also innervated by this nerve. Neither cutaneous branches nor communicating branches with other nerves were found. The present study reveals that the accessory deep peroneal nerve is consistently present and possesses a proper motor and sensory distribution in the lateral region of the leg and ankle. It is not an anomalous nerve as has previously been suggested.     

家兔面神经颅外段的显微解剖

目的　探讨家兔面神经颅外段的主干及分支特点。 方法　健康家兔15只,在显微镜下解剖家兔面神经,并对其形态特点进行观测。 结果　家兔面神经出茎乳孔后分出耳后支、二腹肌支、茎突舌骨肌支及面神经主干。兔面神经主干在面部的分支有颞支、颧支、颊支、下颌缘支和颈支,其中颧支与颊支关系密切,走行过程中合成一干,然后在口角后缘分离。 结论　家兔面神经颧支与颊支在耳廓下缘前部位到口角后缘之间,分支少,神经干较粗,便于进行面神经缺损修复动物模型的建立。     

面神经局部缺血对面神经及面神经核的影响

目的　探讨面神经局部缺血对面神经及面神经核的影响,为临床腮腺切除术提供参考。方法选用家兔,采用同体对照的方法,模拟人腮腺切除手术。实验侧于手术显微镜下,游离面神经并破坏其外血管系,切除腮腺。术后家兔存活4周,观察以下指标：分别检测家兔实验侧和对照侧面神经颊支的传导速度、CMAP波幅和潜伏期;取双侧茎乳孔外面神经干,透射电镜下观察面神经超微结构的变化;取双侧面神经核,Western Blotting法检测面神经核乙酰胆碱转移酶（CHAT）表达的变化,PCR-ELISA法观察面神经核端粒酶活性的变化。 结果　实验侧面神经颊支的传导速度明显低于对照侧、潜伏期明显长于对照侧、波幅明显低于对照侧（P＜0.01,P＜0.05）。实验侧面神经超微结构发生明显变化,以轴索变性为主,包括轴索内微丝增生、断裂,线粒体肿胀、嵴断裂,变性轴索溶解等。实验侧面神经核CHAT的表达和端粒酶活性明显低于对照侧（P＜0.01,P＜0.05）。 结论　游离面神经破坏其外血管系切除腮腺,可导致面神经超微结构发生明显改变、面神经传导功能下降,进而导致面神经核神经元合成乙酰胆碱的含量下降、神经元凋亡增加;提示临床腮腺切除时,应尽可能保护面神经外血管系,以减少面瘫的发生。     

Microsurgical anatomy of the facial nerve trunk

Dissection and manipulation of the facial nerve (FN) trunk between its exit from the cranial base through the stylomastoid foramen (SMF) and its bifurcation is a critical step in various otologic, plastic and neurosurgical procedures. This study demonstrates the anatomical relationships and variability of the FN trunk with emphasis on some important morphometric data, particularly with relevance to hypoglossal-facial nerve anastomosis (HFA). Bilateral microsurgical dissection was performed on twenty-three human cadavers fixed with formalin. The whole trunk of the FN was exposed, its diameter at the SMF and its length were measured, its branches were observed and the site of its bifurcation was determined. Anastomotic connections with other nerves and blood supply of the trunk were studied. The FN invariably emerged from the cranial base through the SMF. Its diameter upon its emergence from the foramen was 2.66 +/- 0.55 mm. Two branches consistently originated from the trunk: the posterior auricular nerve and the nerve to the digastric muscle. Less consistent were the communicating branch with the glossopharyngeal nerve and the nerve to the stylohyoid muscle. The bifurcation of the FN occurred before its penetration into the parotid gland in 15% of cases and within the gland in 85%. The length of the FN trunk was 16.44 +/- 3.2 mm. Anastomoses between the FN and other nerves were observed in one-third of the dissections. The blood supply to the FN trunk was provided by the stylomastoid artery that was identified in 91% of cases. Understanding the microsurgical anatomy of the FN trunk is essential for performing any surgical procedure in the relevant region. Surgical implications of this study are presented with emphasis on HFA surgery.     

Morphological study of the vasa nervorum in the peripheral branch of human facial nerve

Given the length of axons reaching to distal regions, all peripheral nerves must derive nutrient supply not only for the nerve cell body, but also for the peripheral parts. Along the course of a peripheral nerve, in general, nutrient vessels accompany nerve fibers to peripheral regions in the form of "vasa nervorum" derived from the epineurium, reaching the endoneurium through the perineurium and forming a capillary plexus. In addition, in reconstructive procedures in plastic surgery, anastomosis of not only nerves, but also the vasa nervorum, has been reported to achieve improved outcomes. The present study therefore observed morphological features of the blood supply to the distal portion of the facial nerve in 14 sides of 14 adult cadavers (age at death, 46-86 years) under stereo microscopy after dye injection. The region of the epineurium was also observed under scanning electron microscopy (SEM). The vasa nervorum was seen to derive from a complex reticulation structure formed mainly by the superficial temporal, facial, transverse facial and zygomatico-orbital arteries with collateral supply from the supraorbital, deep temporal, buccal arteries and parotid branches. SEM showed that one capillary accompanied each perineurium in each nerve fascicle.     

Surgical anatomy of the preauricular anteroparotid approach for mandibular condyle surgery

Purpose

The different surgical approaches used to treat mandibular condyle fractures are carried out in the periparotid skin area and can lead to facial nerve injury. We conducted a preauricular and anteroparotid surgical approach. Our main aim was to show the anatomical relationship between this approach site and the facial nerve branches, and to define cutaneous landmarks to locate the extraparotid facial nerve branches.

Method

A 2-step dissection of 13 fresh human cadaver semi-heads was performed: a preauricular approach followed by a superficial parotidectomy to visualize the facial nerve. Its course and ramifications were studied and compared to cutaneous landmarks. The proximity of the facial nerve branches with the surgical approach site was observed.

Results

The approach allowed systematically visualising the zygomatic and/or buccal branches. No facial nerve branches were sectioned. In three cases (23 %), a nerve branch was visualized during the approach. The buccal and zygomatic branches were ramified in 77 % of cases.

Conclusions

During our preauricular anteroparotid approach, the buccal and zygomatic branches were visualized but none was sectioned. Most often the approach was carried out between these two branches (46 % of cases). Cutaneous landmarks used were reliable to define a safe and nerve-free area for dissection. The buccal and zygomatic branches are very interesting because their high number of ramifications and anastomoses could serve as nerve relays in case of surgical lesion.     

Formation and distribution of the sural nerve based on nerve fascicle and nerve fiber analyses

The formation and distribution of the sural nerve are presented on the basis of an investigation of 31 legs of Japanese cadavers using nerve fascicle and fiber analyses. Nerve fibers constituting the medial sural cutaneous nerve were designated as 'T', whereas those constituting the peroneal communicating branch were designated as 'F'. In 74.2% of cases (23/31), the T and F fibers joined each other in the leg, whereas in 9.7% of cases (3/31) they descended separately. In 16.1% of cases (5/31), the sural nerve was formed of only the T fibers. The sural nerve gave off lateral calcaneal branches and medial and lateral branches at the ankle. The lateral calcaneal branches always contained T fibers. The medial branches consisted of only T fibers, whereas most of the lateral branches consisted of only F fibers (71.0%; 22/31). In addition to the T and F fibers, P fibers, which derived from the superficial and deep peroneal nerves, formed the dorsal digital nerves. The P fibers were entirely supplied to the medial four and one-half toes. However, they were gradually replaced by the T and F fibers in the lateral direction. The 10th proper dorsal digital nerve consisted of T fibers only (38.7%; 12/31), of F fibers only (19.4%; 6/31) or of both T and F fibers (38.7%; 12/31). These findings suggest that the T fibers are essential nerve components for the skin and deep structures of the ankle and heel rather than the skin of the lateral side of the fifth toe. The designation of the medial sural cutaneous nerve should be avoided and only the T fibers are appropriate components for naming as the sural nerve.     

Correlation of the main peripheral branches of the facial nerve with the cytoarchitectonic subdivisions of the facial nucleus in the guinea pig

Summary Correlation of the main peripheral branches of the facial nerve with morphological subdivisions of the facial nucleus was examined in the guinea pig by the retrograde horseradish peroxidase method. The facial nucleus of the guinea pig was divided cytoarchitectonically into the dorsolateral, lateral, intermediate, medio-intermediate, medial, and ventromedial divisions; the ventromedial division was further divided into the major, dorsal and lateral parts. Six main branches of the facial nerve were identified; the zygomatico-orbital, cervical, posterior auricular, anterior auricular, superior labial, and inferior labial branches. After applying HRP to the main branches of the facial nerve, the pattern of distribution of HRP-labelled neuronal cell bodies within the facial nucleus was examined: the dorsolateral division, dorsal part of the ventromedial division, major part of the ventromedial division, lateral part of the ventromedial division, or medial division contained the cell bodies of respectively the zygomatico-orbital, cervical, posterior auricular, anterior auricular, or superior labial branches, while each of the lateral, intermediate, and medio-intermediate divisions contained the cell bodies of both the superior labial and inferior labial branches.