Skin reference point for the zygomatic branch of the facial nerve innervating the orbicularis oculi muscle (anatomical study)

Purpose

Direct access to the zygomatic branch of the facial nerve in the parotid is less invasive and more selective than first dissecting the nerve trunk and then finding the branches. The aim of this study was to confirm the point of reference on the skin which would give direct access to the zygomatic branch for the orbicularis oculi muscle. The skin reference point studied was on the intertragic notch/external canthus line, 2.5 cm in front of the intertragic notch.

Methods

Ten fresh cadavers, and thus 20 sides of faces were dissected. The zygomatic branch of the facial nerve innervating the orbicularis oculi muscle was accessed directly. The dissection was extended to temporofacial and cervicofacial branches and then to the trunk of the facial nerve by a retrograde path in the parotid.

Results

Twenty dissections of the parotid area confirmed the validity of the anatomical reference point of the zygomatic branch for the orbicularis oculi muscle considered.

Conclusions

The simplicity and reliability of this landmark is important in clinical practice and has numerous potential applications in surgery for rehabilitation of facial paralysis associated with VII healthy and VII affected neurorraphies, in facial paresis for superneurotizations and in traumatology.     

神经电信号中眼轮匝肌功能状态的识别

目的:提取能反映眼轮匝肌功能活动的狗面神经颧支的神经电信号(ENG),通过对ENG信号的分析,识别出眼轮匝肌的功能状态。方法:利用植入到狗面神经颧支周围的Cuff电极提取有闭眼动作发生期间的神经电信号,采用幅度阈值法,通过对ENG信号的分析,识别出闭眼动作发生时眼轮匝肌的收缩动作。结果:研究中我们提取到了能反映闭眼动作发生的ENG信号,并且通过对信号的分析,识别出了眼轮匝肌收缩动作的发生。结论:可以通过对眼轮匝肌支配神经上ENG信号的分析,监控眼轮匝肌的功能状态。     

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。     

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.     

Variability in facial‐muscle innervation: A comparative study based on electrostimulation and anatomical dissection

Facial‐nerve palsy is the most common complication during facial surgery. However, there are few detailed reports on the distribution of the terminal branches of the facial nerve to the mimetic muscles. This also applies to the communicating branches. The aim of our study was to assess the variability of communicant and terminal branches of the facial nerve in humans. This prospective study involved anatomical dissections and intraoperative electric stimulation of facial nerves. We first performed 30 dissections to define the branching patterns of the extracranial facial nerve, with particular focus on the penetrating points into the mimetic muscles. We then studied and compared these preliminary data with 14 operative facial stimulations conducted during parotidectomies. Each trunk and branch received systematic electrostimulation. The electrostimulation and facial‐and‐neck movements were analyzed by two independent reviewers. The peripheral branching and intercommunication of the facial branches were highly variable. Combining electrostimulation and dissections, the frontalis muscle, the depressor labii inferioris and the platysma showed little nerve recuperation whereas the sphincter muscles (orbicularis ori and oculi) were anatomically protected. Facial‐muscle innervation differed among individuals. We found complex variations in the facial branching mode. Our study highlights the branches and corresponding areas that could be considered anatomically risky. Clin. Anat. 32:169–175, 2019. © 2018 Wiley Periodicals, Inc.     

Botulinum toxin paralysis of the orbicularis oculi muscle. Types and time course of alterations in muscle structúre physiology and lid kinematics

In chronically prepared guinea pigs, we investigated the time course of botulinum toxin A's (Bot A) effect on the blink reflex by monitoring lid movements and EMG activity prior to and after Bot A injection into the orbicularis oculi muscle (OOemg), or after nerve crush of the zygomatic nerve. We correlated these alterations with the morphological changes of the orbicularis oculi (lid-closing) muscles of the same animals. After Bot A treatment there was a profound reduction of OOemg activity and blink amplitudes as well as a slowing of maximum blink down-phase velocity. Blink up-phases, however, remained unchanged. Gradual recovery of OOemg magnitude and blink amplitude started around day 6; a functioning blink reflex appeared on day 21, and full recovery of blink amplitude occurred by day 42. Crushing the zygomatic branch of the facial nerve produced similar changes in blink parameters, but recovery was much more rapid (15 days) than for Bot A-treated guinea pigs. The morphological analysis demonstrated that Bot A produced a denervation-like atrophy in the orbicularis oculi. No fiber type-specific alterations were noted, and all muscle fiber types ultimately recovered, with no long-standing consequences of the transient denervation. Our findings support the notion that functional recovery was the result of preterminal and terminal axonal sprouting that subsequently re-establishes functional innervation. Moreover, differences between the present findings and those seen after injection of Bot A into the extraocular muscles strongly support the hypothesis that the composition in terms of muscle fiber type and the properties of the motor control system of a given muscle greatly influence both how the particular muscle responds to toxin injection, and how effective the toxin is in resolution of neuromuscular disorders that affect a particular muscle. The present findings were consistent with clinical observations that Bot A produces only temporary relief in patients with essential blepharospasm. It is likely that the efficacy of Bot A in treatment of blepharospasm could be improved by using agents that suppress terminal sprouting. The close correspondence of the changes in blink physiology between human patients and guinea pigs after Bot A treatment demonstrate that the guinea pig is an excellent model system for testing strategies to prolong the beneficial effects of Bot A treatment in relieving lid spasms in human subjects.     

The malaris muscle: its morphological significance for sustaining the intraorbital structures

The orbicularis oculi muscle, an important mimetic muscle, was investigated to ascertain its anatomical relation to facial aging—especially its orbital part (Oo). Previous studies of the distinct muscle bundles frequently found inferior to the Oo have provided various definitions, including that of the malaris muscle. This study aimed to examine these muscle bundles and clarify their function in facial aging. Twelve heads of Japanese cadavers (average age: 82.5 years old) were dissected to observe the muscles, focusing in particular on those in the periorbital region. Six specimens were further dissected from the inner surfaces to examine the patterns of facial nerve branches under the operating microscope. Histological examinations of two head halves were carried out to investigate the relationship between the muscle bundles and the intraorbital structures. Muscle bundles consisting of lateral, medial, and U-shaped suspending bundles were observed in the region inferior to the Oo. Lateral and suspending bundles were found in all specimens, while the medial bundles were noted in only 9 of 22 specimens. Some branches of the facial nerve penetrated through the lateral, medial, and suspending bundles. The relationship between the suspending bundles and the protruding orbital fat was assessed. The muscle bundles found in this study were regarded as the malaris muscle—a transitional muscle between the superficial and deep facial layers. The suspending bundle may play a role in sustaining the intraorbital structures.     

Topographical anatomy of the transverse facial artery

The transverse facial artery (TFA) is found in the lateral face and supplies the parotid gland and duct, facial nerve, facial muscles, and skin. To better understand the cutaneous vascularization of the lateral face and to better characterize the topography and other anatomical features of the TFA, microsurgical dissection was performed in 44 cadavers. The number of TFAs present ranged from one to three, and a single TFA was most common (70.5%). The TFA originated from the superficial temporal artery at or above the level of crossing by the temporofacial trunk of the facial nerve in the parotid gland (57.6%). The TFA divided into superior and inferior trunks in the gland, and continued as emerging branch. The superior emerging branch emerged from the gland superior to the parotid duct and divided into many branches. It supplied the malar area, crossed the parotid duct, terminated as perforator, vasa nervorum, or artery to the parotid duct or muscle. The inferior trunk in 72.5% continued as emerging branch instead of terminating in the gland. TFAs were classified into four types; the most common type was Type A in which the superior and inferior emerging branches and the duct‐crossing branch were present. The mean number of perforators to the superficial cutaneous layer was 1.9. Most perforators extended from the superior emerging branches (77.9%). The most common perforating site was below the duct on the anterior third of the masseter muscle. In two cases, the TFA formed an anastomosis with the facial artery. Clin. Anat. 23:168–178, 2010. © 2009 Wiley‐Liss, 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.     

口轮匝肌双侧神经电图测试意义的临床和实验探讨

目的通过口轮匝肌双侧神经电图测试,探讨口轮匝肌的神经支配及面神经麻痹侧眼轮匝肌和口轮匝肌受损伤程度差异。方法测试正常人30人,面瘫患者152例的双侧神经电图(ENoG),并计测非刺激侧(患侧)对刺激侧(健侧)的振幅百分比值。其中失神经支配阴性组52例,失神经支配I度组41例,Ⅱ度组32例,Ⅲ度组27例。制作豚鼠压榨性面瘫实验模型,分别计测第1次加压5秒组和第2次加压5秒组的口轮匝肌双侧ENoG,并分别计测出第一次压榨组和第二次压榨组压榨后非刺激侧振幅值和刺激侧振幅值。结果面瘫组非刺激侧(患侧)对刺激侧(健侧)双侧ENoG振幅比值失神经支配Ⅲ度组显著大于Ⅱ度组(P0.05),失神经支配Ⅱ度组显著大于Ⅰ度组(P0.05),失神经支配Ⅰ度组显著大于失神经支配阴性组,失神经支配阴性组显著大于正常人组(P0.05)。实验动物组第2次压榨组非刺激侧振幅值显著大于第1次压榨组(P0.05),第1次压榨组非刺激侧振幅值显著大于压榨前振幅值(P0.05)。结论口轮匝肌受双侧面神经支配是面神经失神经支配后口轮匝肌比眼轮匝肌受损伤程度小的原因之一。患侧对健侧振幅百分比值越大,患侧面神经受损伤程度越重。     

On the a. malaris of the goat (Capra hircus)

Detailed observations were made of the a. malaris in 25 adult goats by means of the acryl plastic injection method and the findings obtained were evaluated in comparison with those for other mammals. The malar artery arose from the superior wall of the infraorbital artery, lateral to the infraorbital nerve and superomedial to the maxillary tuber, independently or rarely in common with the superior alveolar artery. It first passed anterolaterally in the sulcus malaris on the superior surface of the lacrimal bulla and gave rise to the third palpebral branch independently or rarely in common with the inferior oblique muscular branch beneath the obliquus inferior muscle, and also the main and accessory inferior oblique and the maxillary sinus branches. The third palpebral branch gave off the periosteal, the conjunctive, the supero- and inferolateral branches. After the malar artery gave off the zygomatic branch on the orbital surface of the zygomatic bone, it passed anterosuperiorly up to the incisura malaris at the medial end of the infraorbital margin of the lacrimal bone and gave off the medial superior and inferior palpebral arteries or a common trunk between them. It continued to pass forwards as the nasal radical branch after giving off the infraorbital marginal branch and anastomosed with the nasal dorsal branch of the superficial temporal artery. The medial inferior palpebral artery formed the inferior palpebral arterial arch by anastomosing with the lateral inferior palpebral artery of the superficial temporal at the lateral canthus. The inferior palpebral marginal, the ocular orbicular muscular and the conjunctive branches diverged from the above arterial arch. The medial superior palpebral artery gave off the lacrimal canalicular and the nasolacrimal canal branches and anastomosed with the lateral superior palpebral artery or the frontal branch of the superficial temporal at the medial canthus. The characteristic features of the malar artery in the goat were thus the third palpebral branch occasionally diverging from the external ophthalmic artery of the maxillary artery, a main and several accessory inferior oblique muscular, the maxillary sinus branches and the zygomatic branches.     

Findings of unique small muscle fibers at the superficial portion of the orbicularis oculi in the lateral canthal region of Japanese adult cadavers

This study reports the existence of previously unknown muscle fascicles in Japanese adult cadavers. A bundle of these muscle fascicles diverged from the pretarsal portion of the orbicularis oculi muscle and coursed in a lateral direction superficial to this muscle. When observed with the naked eye, the bundle seemed to originate at the medial canthus and run along or near the edge of the upper eyelid. However, its boundary with the orbicularis oculi muscle was indistinguishable until it crossed superficial to this muscle. Throughout our observations, the thin muscle bundle was identified with high frequency (94%, 49 of 52 individual cadavers), and is thus unlikely to be an artifact. Light microscopy revealed that, in sagittal sections, the thin muscle bundle was located on the superficial side of the lateral portion of the orbicularis oculi muscle, while in horizontal sections, it ran in a superficial plane to the orbicularis oculi muscle in a medial to lateral direction. Despite having some similarity to a muscular raphe, the lateral canthal band, and to one of the previously known inferior muscles of the orbicularis oculi muscle, the results of our anatomical study suggest that the bundle is none of these. Rather, it is a previously unreported muscle that likely contributes to the surface morphology at the lateral canthus. Clin. Anat. 23:637–641, 2010. © 2010 Wiley‐Liss, Inc.     

The facial artery of the common marmoset (Callithrix jacchus)

The facial artery and its ramifications in 7 adult common marmosets (Callithrix jacchus) were studied by the plastic injection method. The findings obtained are discussed in comparison with those for other primates. In the submandibular region, the facial artery arose from the external carotid artery at the height of the atlas via the linguofacial trunk on 10 of the total of 14 sides examined and independently on the other 4 sides. This common trunk always gave rise to the superior thyroid artery. The facial artery passed anterolaterally between the styloglossus muscle and the intermediate tendon of the digastricus muscle, giving off the styloglossal and the submandibular glandular branches, and anteroinferiorly medial to the pterygoideus medialis muscle. In a position anterior to this muscle, the submental artery and masseteric branch were derived. The submental artery gave off the medial pterygoid, the digastric, the cutaneous, the sublingual glandular and the mylohyoid branches, and then continued up to the median line, where it terminated to supply the genioglossus muscle. In the facial region, the facial artery passed anterosuperiorly along the anterior margin of the masseter muscle on 12 sides and away from it forwards on 2 sides, giving off the premasseteric branch in one of these 2 sides. It gave rise to the cutaneous, the buccal and the buccinator branches, the inferior labial artery and the communicating branch with the zygomatic artery. It terminated to divide into the superior labial and the naris lateral arteries, although the latter was lacking on 4 sides. The inferior labial artery gave off the mandibular marginal, the inferior labial marginal and the inferior labial glandular branches and terminated to anastomose with the mental artery. The superior labial artery divided into the superficial and deep branches, each of which continued as a nasal septal branch. The facial artery of the common marmoset usually ascended along the anterior margin of the masseter muscle and did not reach the medial angle of the eye.     

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.     

Detailed anatomy of the abducens nerve in the lateral rectus muscle

The aims of this study were to elucidate the detailed anatomy of the abducens nerve in the lateral rectus muscle (LRM) and the intramuscular innervation pattern using Sihler staining. In this cohort study, 32 eyes of 16 cadavers were assessed. Dissection was performed from the LRM origin to its insertion. The following distances were measured: from LRM insertion to the bifurcation point of the abducens nerve, from LRM insertion to the entry site of the superior branch or inferior branch, from the upper border of the LRM to the entry site of the superior branch, from the lower border of LRM to the entry site of inferior branch, and the widths of the main trunk and superior and inferior branches. The single trunk of the abducens nerve divided into two branches 37 mm from insertion of the LRM, and 22 of 32 (68.8%) orbits showed only two superior and inferior branches with no subdivision. The superior branch entered the LRM more anteriorly (P = 0.037) and the superior branch was thinner than the inferior branch (P = 0.040). The most distally located intramuscular nerve ending was observed at 52.9 ± 3.5% of the length of each muscle. Non‐overlap between the superior and inferior intramuscular arborization of the nerve was detected in 27 of 32 cases (84.4%). Five cases (15.6%) showed definite overlap of the superior and inferior zones. This study revealed the detailed anatomy of the abducens nerve in the LRM and provides helpful information to understand abducens nerve palsy. Clin. Anat. 30:873–877, 2017. © 2017 Wiley Periodicals, Inc.     

Role of proprioception in the control of lid position during reflex and conditioned blink responses in the alert behaving cat

The contribution of the orbicularis oculi muscle to the determination of lid position, and the putative role of eyelid proprioception in the control of reflex and conditioned eye blinks, were studied in alert behaving cats. Upper lid movements and the electromyographic activity of the orbicularis oculi muscle were recorded during reflexively evoked blinks and during the classical conditioning of the eyelid response. Blinks were evoked by air puffs, flashes and electrical stimulation of the supraorbitary branch of the trigeminal nerve. Eyelid responses were conditioned with a trace classical conditioning paradigm consisting of a short, weak air puff, followed 250 ms later by a long, strong air puff. Orbicularis oculi muscle activation during reflex blinks was independent of lid position and was not modified by the presence of weights acting in the upward or downward directions. Local anesthesia of the supraorbital nerve reduced blinks evoked by air puffs applied to the lower jaw, but did not affect flash-evoked blinks. No relationship was established between initial lid position and the first downward component of conditioned eyelid responses. In contrast, initial lid position was related to the first upward component of the same conditioned response.

It is concluded that orbicularis oculi motor units receive no feedback proprioceptive signals from the eyelid, other than those coming from cutaneous receptors, and that lid position is determined by the activity of the levator palpebrae superioris muscle. The lack of sensory information about lid position in facial motoneurons probably has some functional implications on the central control of cognitive and emotional facial expressions.     

Innervation of human soft palate muscles

Our objective was to determine the branching and distribution of the motor nerves supplying the human soft palate muscles. Six adult specimens of the soft palate in continuity with the pharynx, larynx, and tongue were processed with Sihler's stain, a technique that can render large specimens transparent while counterstaining their nerves. The cranial nerves were identified and dissection followed their branches as they divided into smaller divisions toward their terminations in individual muscles. The results showed that both the glossopharyngeal (IX) and vagus (X) nerves have three distinct branches, superior, middle, and inferior. Only the middle branches of each nerve contributed to the pharyngeal plexus to which the facial nerve also contributed. The pharyngeal plexus was divided into two parts, a superior innervating the palatal and neighboring muscles and an inferior innervating pharyngeal constrictors. The superior branches of the IX and X nerves contributed innervation to the palatoglossus, whereas their middle branches innervated the palatopharyngeus. The palatoglossus and palatopharyngeus muscles appeared to be composed of at least two neuromuscular compartments. The lesser palatine nerve not only supplied the palatal mucosa and palatine glandular tissue but also innervated the musculus uvulae, palatopharyngeus, and levator veli palatine. The latter muscle also received its innervation from the superior branch of X nerve. The findings would be useful for better understanding the neural control of the soft palate and for developing novel neuromodulation therapies to treat certain upper airway disorders such as obstructive sleep apnea.     

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.