A Cadaveric Study of Dye Spreading: Determining the Ideal Injection Pattern for Masseter Hypertrophy.

BACKGROUND: Masseter hypertrophy is the main cause of an asymmetrical and squared lower facial contour in the Asian community. Botulinum toxin injection technique is crucial to treat this condition. OBJECTIVE: To improve injection techniques for masseter hypertrophy by elucidating the distribution of the injections within the masseter. METHODS: Thirty masseter muscles were divided into 6 groups of 5 muscles each. Each group received one 0.2- or 0.3-mL injection at Point A, B, or C according to a three-point technique. Muscle dimensions and dye of the primary and secondary dye spreading were measured. RESULTS: The average muscle length, width, and thickness were 69.87, 33.50, and 11.23 mm, respectively. The average primary longitudinal and horizontal spreading was 36.56 and 15.60 mm, respectively. No statistically significant difference was found between 0.2- and 0.3-mL injections at each point. CONCLUSION: The three-point technique best fits in the safe zone and should be the standard injection technique for masseter hypertrophy. Injection at Points B and C may create secondary spreading that affect the risorius muscle and the parotid gland which are the cause of asymmetrical smiling and xerostomia, respectively. The dosage should be adjusted according to the muscle volume and not only the thickness.

Clinical implications of the arterial supplies and their anastomotic territories in the nasolabial region for avoiding arterial complications during soft tissue filler injection.

INTRODUCTION: The nasolabial fold (NLF) causes particular concern during aging in the middle face region. However, arterial complications of filler injections at this site have been continually reported during recent years. The aim of this study was to investigate the arterial locations and their anastomotic pathways related to filler injection sites in the NLF. MATERIALS AND METHODS: Thirty hemi-faces of 15 embalmed Thai cadavers were dissected. Three anatomical landmarks of NLFs were assigned: the inferior margin level (NLF1), the mid-philtral horizontal line level (NLF2), and the inferior alar level (NLF3). Ten hemi-faces of five soft embalmed Thai cadavers underwent a modified Sihler's staining procedure to investigate the arterial anastomoses. RESULTS: The artery closest to all of the landmarks was the facial artery. It was located inferomedial to NLF1 in 28%, and the mean distances along the X- and Y-axes were 3.53 ± 2.11 mm and 3.53 ± 1.75 mm, respectively. It was also located medial to NLF2 in 52.1% with an X-axis distance of 4.93 ± 1.53 mm. Several arteries were located close to NLF3, including the facial (33.3%), lateral nasal (33.3%), and infraorbital (30.0%) arteries. Anastomoses of the nasolabial arteries served to connect both the external-external and internal-external carotid systems. CONCLUSIONS: Several arteries are located close to NLF1-NLF3. To prevent arterial injury, the locations and anastomotic pathways, as possible sources of severe complications, should be recognized prior to NLF filler injection.

Cadaveric Dissections to Determine Surface Landmarks Locating the Facial Artery for Filler Injections.

BACKGROUND: The facial artery is a high-risk structure when performing filler injections at the nasolabial fold, buccal, and mandibular regions. OBJECTIVES: This study aimed to establish reference landmarks locating the course of the facial artery and its essential branches. METHODS: Thirty-one embalmed cadavers were enrolled in this study. The course of the facial artery was observed in regard to the following reference points: masseter insertion, oral commissure, and common bony landmarks. The corner of the mouth was utilized as the landmark to measure the turning point of the facial artery. RESULTS: Seven points were established to identify the course and turning point of the facial artery. These included the anterior masseteric, lateral mental, infraorbital, medial canthal, basal alar, post-modiolar (PMP), and supra-commissural (SCP) points. The course of the facial artery deviates at least twice at the lateral mental points and at the SCP or PMP. The facial artery appeared more medially when the artery turned at the PMP and SCP. It presented through the lateral channel if the turning point was solely at the PMP. Wherever the facial artery deviates, it can be divided into 3 segments: the mandibular, buccal, and nasolabial segments. The arterial course may deviate laterally from the mouth corner towards PMP. The nasolabial segment may also deviate laterally to the basal alar point at the alar grove for 0.5 to 1 cm. CONCLUSIONS: The deviation of facial artery closely relates with mandibular, buccal, and nasolabial segments. It is essential in avoiding arterial injury for physicians and surgeons who perform procedures in these areas.

Three-Dimensional Evaluation of the Depressor Anguli Oris and Depressor Labii Inferioris for Botulinum Toxin Injections.

BACKGROUND: Botulinum toxin type A (BoNT-A) injection administered at an inappropriate site or depth can produce an unwanted change in facial animation because the depressor anguli oris (DAO) and depressor labii inferioris (DLI) muscles are partially overlapped. Therefore, simple BoNT-A injection guidelines, based on 3-dimensional (3D) facial anatomic references and landmarks, would be very useful. OBJECTIVES: The aim of this study was to establish novel BoNT-A injection guidelines that include the soft tissue thickness at the lower perioral region. Data were acquired with a 3D scanning system combined with dissections in order to obtain accurate injection sites and depths for the DAO and DLI. METHODS: 3D scans of the facial skin, superficial fat, and facial muscle surface were performed in 45 embalmed cadavers. The thicknesses of the skin and subcutaneous layer were calculated automatically from superimposed images at each of 5 reference points (P) in the perioral region. RESULTS: In every case (100%), P3 and P5 were located in the DLI and DAO areas, respectively (45/45). Therefore, we defined P3 as the "DLI point" and P5 as the "DAO point." The soft tissue thicknesses at the DLI and DAO points were 6.4 [1.7] mm and 6.7 [1.8] mm, respectively. CONCLUSIONS: The P3 and P5 described in this study are effective guidelines that only target the DLI and DAO. Clinicians, specifically, can easily use facial landmarks, such as the cheilion and pupil, to assign the DLI and DAO points without any measurement or palpation of the modiolus.

Localization and Topography of the Arteries on the Middle Forehead Region for Eluding Complications Following Forehead Augmentation: Conventional Cadaveric Dissection and Ultrasonography Investigation.

Forehead augmentation with filler injection is one of the most dangerous procedures associated with iatrogenic intravascular injection resulting in the severe complications. Nonetheless, few studies have determined the explicit arterial localization and topography related to the facial soft tissues and landmarks. Therefore, this study aimed to determine an arterial distribution and topography on the middle forehead region correlated with facial landmarks to grant an appropriate guideline for enhancing the safety of injection. Nineteen Thai embalmed cadavers were discovered with conventional dissection and 14 Thai healthy volunteers were investigated with ultrasonographic examination on the middle forehead. This study found that at the level of mid-frontal depression point, the transverse distance from the medial canthal vertical line to the superficial and deep branches of supraorbital artery were 9.1 mm and 15.1 mm, respectively. Whereas the depths from the skin of these arteries were 4.1 mm and 4.3 mm, respectively. Furthermore, the frontal branch of superficial temporal artery was detectable in 42.1% as an artery entering the forehead area. At the level of lateral canthal vertical line, the vertical distance of frontal branch was 31.6 mm, and the depth from skin of the artery was 2.7 mm. In conclusion, a proper injection technique could be performed based on an intensive arterial distribution and topography, and ultrasonographic examination before the injection is also suggested in order to restrict the opportunity of severe complications.

Three-Dimensional Territory and Depth of the Corrugator Supercilii: Application to Botulinum Neurotoxin Injection.

This study aimed to determine the three-dimensional (3D) territory and depth of the corrugator supercilii muscle (CSM) using a 3D structured-light scanner. Thirty-two hemifaces from Korean and Thai embalmed cadavers were used in this study, and 35 healthy young Korean subjects also participated. A 3D analysis of the CSM territory and depth was performed using a structured-light 3D scanner. The most frequently observed locations of the CSM identified in the cadaver were confirmed in healthy young subjects using a real-time two-dimensional B-mode ultrasonography system. The CSM was present in all of the cadavers and healthy young subjects at the intersection point between the vertical line passing through the medial canthus and the horizontal line passing through the glabella (Point #6). The CSM was located on the medial side of the lateral limbus in most cases. The most-medial and most-lateral origin points were at depths of 5.7 ± 1.4 mm (mean ± SD) and 6.6 ± 1.4 mm, respectively; the corresponding depths of the insertion points were 5.4 ± 1.4 mm and 5.6 ± 2.1 mm, respectively. The origin and insertion points of the CSM were at similar depths. The injection depth should be around 4 mm for botulinum neurotoxin (BoNT) injections into the CSM. Point #6 could be regarded as an effective target point for managing the glabellar frown line and preventing palpebral ptosis when injecting BoNT into the CSM. Clin. Anat., 33:795-803, 2020. © 2019 Wiley Periodicals, Inc.

Anatomical and Ultrasonography-Based Investigation to Localize the Arteries on the Central Forehead Region During the Glabellar Augmentation Procedure.

Glabellar augmentation is one of the most popular cosmetic procedures but can entail severe complications caused by inadvertent intravascular injection of filler. Nevertheless, few studies have investigated the arteries on the glabellar and central forehead regions. The aim of this study was to correlate the topography and location of the arteries in this area with anatomical landmarks to propose a safety guideline. Two methods were used to investigate the glabellar and central forehead areas: dissection of 19 Thai embalmed cadavers, and ultrasonographic examination of 14 healthy Thai volunteers. At the level of the glabellar point, the horizontal distances from the midline to the arteries were 4.7 mm (central artery), 7.8 mm (paracentral artery), and 14.7 and 19.2 mm (superficial and deep branches of supratrochlear artery). The depths from the skin of the arteries were 3.1 mm (central artery), 4.8 mm (paracentral artery), and 4.2 and 5.9 mm (superficial and deep branches of supratrochlear artery). The periosteal artery was detected in 71.1% as a branch of either the superior orbitoglabellar or the supratrochlear artery. It ran in the supraperiosteal layer for a short course and penetrated the periosteum above the superciliary ridge or above the medial eyebrow, adhering tightly to the bony surface. This study suggests a safe injection technique for the glabella based on a thorough knowledge of arterial distribution and topography and color Doppler ultrasonographic examination prior to the injection, which is recommended to minimize the risk of severe complications. Clin. Anat. 33:370-382, 2020. © 2019 Wiley Periodicals, Inc.

A novel anatomical consideration on the exposed segment of the facial artery.

An understanding of the location and depth of the facial artery (FA) is essential in aesthetic surgery and various cosmetic procedures. The purpose of this study was to clarify the three-dimensional (3D) topography of the exposed segment (ES) of the FA and to provide information to help minimize complications during clinical procedures. From 50 embalmed adult cadavers, the undissected and dissected hemifaces were scanned and reconstructed using the 3D scanner. Then the topographic location of the ES was identified and measured from the superimposed the 3D images. The ES was observed in 82% of the whole specimens. The exposure patterns of the ES were examined, and classified into three types: Type I, one site exposed pattern (74%); Type II, two sites exposed pattern (8%); and Type III, nonexposed pattern (18%). The extent of the ES was located at 2.2 mm above and 4.2 mm below the cheilion (Ch)-otobasion inferius line, and 20.0 to 25.2 mm from the Ch on the lateral aspect. In the frontal view, the average distance from the mid-pupillary line to the ES was 7.1 mm, and from the lateral canthal line to the ES was 6.1 mm. The ES was 7.6 mm below the skin surface. The results of this study will help to provide safe guidelines for filler injections as well as selecting the safe regions in various clinical procedures. Clin. Anat. 33:257-264, 2020. © 2019 Wiley Periodicals, Inc.

Classification of unusual insertion of the pectoralis minor muscle.

PURPOSE: The pectoralis minor muscle (PMi) generally originates from the third, fourth, and fifth ribs and inserts on the medial and superior margins of the anterior portion of the coracoid process. Variations in the shape and attachment point of the PMi could cause discomfort in the shoulders. The aim of this study was to observe the types of morphological insertion patterns and attachment sites of the PMi. METHODS: Seventy-four sides of fresh, embalmed Korean (42 sides; mean age 78 years) and Thai (32 sides; mean age 78 years) cadavers were dissected to analyze the morphological insertion types and attachment sites of the PMi. RESULTS: Unusual insertion patterns were evident in about 23% of the samples. When the portion of the PMi tendon ran over the coracoid process, the most common attachment site was the glenohumeral joint capsule. We also confirmed the attachment of the PMi to the clavicle. Costal attachments of the PMi that extend from the second rib to the fourth rib were observed frequently as well. CONCLUSIONS: Unusual insertion patterns of the PMi are common. Some authors consider that tendon attachment to the joint capsule can cause shoulder pain. In addition, the PMi tendon could be utilized in acromioclavicular joint reconstruction. Surgeons need to be aware of the possibility of a PMi variant being found during surgery even when this is not visible in magnetic resonance or ultrasound imaging.

A Dark Side of the Cannula Injections: How Arterial Wall Perforations and Emboli Occur.

BACKGROUND: Though most injectors prefer to use a cannula rather than a needle, there have been reported cases of blindness following cannula injections. This study investigated possible situations in which a cannula can injure an artery to gain more insight about the vascular complication and its prevention. METHODS: To understand how an arterial injury occurs, five situations favoring vascular injury were simulated and tested. Experiments were performed in 100 arterial segments of 10 soft embalmed cadavers with red latex injections to the arteries. The frontal branch of the superficial temporal artery with a diameter between 1.2 and 1.5 mm was chosen for the experiment with a 25G cannula. Five situations were created to simulate any possibility that the cannula can penetrate through the arterial wall. Two factors were varied for simulation of specific danger situations. Factors that vary were as follows: (1) the angles between the cannula and the artery when the cannula touched the artery, and (2) the segments of the artery with different features. RESULTS: The cannula could penetrate the arterial wall in some specific situations with a different chance in each situation. The perpendicular angle between the artery and the cannula was one of the essential situations for vascular injury. Situations that had a similar effect of the perpendicular arterial surface related to the cannula axis also favored vascular injuries. CONCLUSION: During a blinded insertion of cannula injections to reach the target area, the injector cannot discriminate the sensation at the cannula tip between the resistance of a fibrous septum in the way of the insertion and the resistance of encountering an artery. To prevent arterial emboli, the cannula trajectory should not be close to the main artery in the region. This allows a physician to safely perform an intermittent forceful insertion without an arterial injury during an attempt to perform a gentle cannula insertion. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors. www.springer.com/00266 .

Cadaveric Assessment of Lip Injections: Locating the Serious Threats.

BACKGROUND: Lip augmentation could be a possible cause of blindness following filler injections. This study evaluated the risk by simulating clinical scenarios of marginal injections to the upper and lower lips and then evaluated the risk of vascular injuries. METHODS: A 22G cannula was inserted bilaterally along the wet-dry junction of the upper and lower lip margins in fifteen cadavers, and then both lips were dissected to verify possible injuries to the superior and inferior labial arteries. The position of the labial arteries in the vermilion zone was documented to determine the appropriate injection technique. RESULTS: In the marginal injections to the lips, arterial injuries occurred at the medial segment of the vermilion zone of both the upper and lower lips, at the terminal part of the labial arteries or a distal branch. Considering arterial anatomy, the upper lip has a higher chance of arterial injury than the lower lip. The cannula should not be inserted in the submucosa as it is recommended to evert the vermilion because both the superior and inferior labial arteries are located in the submucosa of the medial and middle segments of the vermilion in all specimens. CONCLUSION: Awareness of the possibility of vascular injury is necessary during injections of the medial segments of the vermilion of the lips. Vermilion border and marginal injections are recommended for safe and effective lip augmentation. Deep injection around the oral commissure and submucosal injection of the medial and middle segments of the vermilion zone are prohibited because of the high risk of arterial injury. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Periorbital and Intraorbital Studies of the Terminal Branches of the Ophthalmic Artery for Periorbital and Glabellar Filler Placements.

BACKGROUND: Filler injections for sunken upper eyelid correction and glabellar augmentation at the orbitoglabellar region need to be performed correctly. Precise knowledge of the emerging sites of all terminal branches of the ophthalmic artery is essential for these procedures to be conducted safely. METHODS: The terminal branches of the ophthalmic artery were studied in both periorbital and intraorbital dissections. The aim of this study was to verify the critical positions of the emerging sites at the orbital septum that may act as potential retrograde channels for filler emboli. RESULTS: In the 40 eyes examined, the branches of the ophthalmic artery were found to emerge from four different sites. Two substantial emerging sites were situated on both sides of the trochlea of the superior oblique muscle. These sites were located at the superior part of the medial orbital rim (SMOR) and are alternatively named as the epitrochlear and the subtrochlear emerging sites. The other two sites can be regarded as accessory emerging sites due to the comparably smaller artery. Dissection of the intraorbital region revealed small periosteal branches of the infraorbital artery which coursed anteriorly on the orbital floor to form anastomoses with the lacrimal artery. In other areas of the orbital floor, no branches extended from the infraorbital artery. In front of the lacrimal gland, very minute branches descended and coursed along both margins of the superior tarsus but did not course outside the lateral orbital rim. CONCLUSION: A danger zone was located at the SMOR, where the ophthalmic branches emerge to form anastomotic channels. Compression at the trochlea guarantees safe injection of filler, reducing the risk of complication. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Facing the Worst Risk: Confronting the Dorsal Nasal Artery, Implication for Non-surgical Procedures of Nasal Augmentation.

BACKGROUND: The nose is a dangerous site for filler injection. This study investigated the anatomy of the dorsal nasal artery at the upper part of the nose to clarify how ocular complications occur. METHODS: Dissections were performed in 50 noses of the embalmed cadavers. Either the soft embalming or formaldehyde embalming processes were used. RESULTS: The dorsal nasal artery is not a constant artery. The artery traveled in the subcutaneous tissue layer of the nasal dorsum on the transverse nasalis muscle and its midline nasal aponeurosis which connected the muscles on both sides. Bilateral dorsal nasal arteries existed only in 34%. In 28% of the specimens, a single and large dorsal nasal artery was presented. The diameter was 0.4 ± 0.2 mm when bilateral dorsal nasal arteries were present and 0.7 ± 0.3 mm in a single artery. The largest artery was 1.2 mm. The artery usually crossed the midline at the middle third part of the nose over the upper lateral cartilages to form an anastomosis with the contralateral lateral nasal artery as the oblique nasal artery in 14%. The artery might descend and communicate with the ipsilateral lateral nasal artery in 6% or descended as a midline artery and form the nasal tip plexus in 8%. In 38% of the specimens, the arteries became small, formed a subcutaneous plexus and randomly distributed on the superficial layer of the subcutaneous tissue in the upper two-thirds of the nose. CONCLUSION: During the injections at the upper (bony) and middle (cartilaginous) part of the nose for nasal dorsal augmentation, the injector has to make sure the cannula tip is in the preperiosteal plane by reinsertion of the cannula if needed, due to the chance of encountering the large single dorsal nasal artery at the midline. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Novel Anatomic Description of the Course of the Inferior Palpebral Vein for Minimally Invasive Aesthetic Treatments.

BACKGROUND: The inferior palpebral vein (IPV) receives tributaries from the inferior palpebral part of the orbicularis oculi muscle (OOc). The aim of this study was to elucidate the venous distribution pattern of the IPV for dermal filler injection. MATERIAL AND METHODS: Fifty hemifaces from 34 cadavers were used in this study. The various distribution patterns of the IPV were classified according to its relationship with the angular vein (AV) and facial veins. RESULTS: The IPV can be classified into the following 4 types: Type I (58.0%), in which the origin of the IPV is located beneath the lateral part of the OOc; Type II (12.0%), in which the origin of the IPV is located beneath the inferior part of the OOc; Type III (8.0%), in which the origin of the IPV is located beneath both the lateral and inferior parts of the OOc; and Type IV (22.0%), in which the IPV is undeveloped. CONCLUSION: The course of the IPV can be approximated by connecting the lateral orbital rim to the C point (the meeting point between the IPV and the AV). The lateral rim can be palpated and the location of the C point is suggested as a columnar area inferior to the pupil.

A Cadaveric Study of the Communication Patterns Between the Buccal Trunks of the Facial Nerve and the Infraorbital Nerve in the Midface.

Most nerve communications reported in the literature were found between the terminal branches. This study aimed to clarify and classify patterns of proximal communications between the buccal branches (BN) of the facial nerve and the infraorbital nerve (ION).The superficial musculoaponeurotic system protects any communication sites from conventional dissections. Based on this limitation, the soft tissues of each face were peeled off the facial skull and the facial turn-down flap specimens were dissected from the periosteal view. Dissection was performed in 40 hemifaces to classify the communications in the sublevator space. Communication site was measured from the ala of nose.A double communication was the most common type found in 62.5% of hemifaces. Triple and single communications existed in 25% and 10% of 40 hemiface specimens, respectively. One hemiface had no communication. The most common type of communication occurred between the lower trunk of the BN of the facial nerve and the lateral labial (fourth) branch of the ION (70% in 40 hemifaces). Communication site was deep to the levator labii superioris muscle at 16.2 mm from the nasal ala. Communications between the motor and the sensory nerves in the midface may be important to increase nerve endurance and to compensate functional loss from injury.Proximal communications between the main trunks of the facial nerve and the ION in the midface exist in every face. This implies some specific functions in normal individuals. Awareness of these nerves is essential in surgical procedure in the midface.

Safe Planes for Injection Rhinoplasty: A Histological Analysis of Midline Longitudinal Sections of the Asian Nose.

BACKGROUND: Dorsal nasal augmentation is an essential part of injection rhinoplasty on the Asian nose. Aesthetic physicians require detailed knowledge of the nasal anatomy to accurately and safely inject filler. METHODS: One hundred and thirty-five histological cross sections were examined from 45 longitudinal strips of soft tissue harvested from the midline of the nose, beginning from the glabella to the nasal tip. Muscles and nasal cartilage were used as landmarks for vascular identification. RESULTS: At the nasal tip, a midline longitudinal columellar artery with a diameter of 0.21 ± 0.09 mm was noted in 14 cadavers (31.1 %). At the infratip, subcutaneous tissue contained cavernous tissue similar to that of the nasal mucosa. The feeding arteries of these dilated veins formed arteriovenous shunts, into which retrograde injection of filler may be possible. All of the nasal arteries present were identified as subcutaneous arteries. They coursed mainly in the superficial layer of the subcutaneous tissues, with smaller branches forming subdermal plexuses. A substantial arterial anastomosis occurred at the supratip region, in which the artery lay in the middle of the subcutaneous tissue at the level of the major alar cartilages. These arteries had a diameter ranging between 0.4 and 0.9 mm and were found in 29 of 45 specimens (64.4 %). This was at the level midway between the rhinion above the supratip and the infratip. This anastomotic artery also crossed the midline at the rhinion superficial to the origin of the procerus on the lower end of the nasal bone. Here the arterial diameter ranged between 0.1 and 0.3 mm, which was not large enough to cause arterial emboli. Fascicular cross sections of the nasalis muscle directly covered the entire upper lateral cartilage. The subdermal tissue contained few layers of fat cells along with the occasional small artery. The procerus arose from the nasal bone and was continuous with the nasalis in 16 cadavers (35.6 %). There was fatty areolar tissue between the procerus and the periosteal layer and no significant arteries present. The procerus ascended beyond the brow to insert into the frontalis muscle with very few cutaneous insertions. The supratrochlear vessels and accompanying nerve were occasionally found on the surface of the frontalis muscle. CONCLUSION: Most nasal arteries found in the midline are subcutaneous arteries. Filler should be injected deeply to avoid vascular injury leading to compromised perfusion at the dorsum or filler emboli at the nasal tip. LEVEL OF EVIDENCE V: This journal requires that the authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Characterizing the Lateral Border of the Frontalis for Safe and Effective Injection of Botulinum Toxin.

BACKGROUND: The forehead is a common site for injection of botulinum neurotoxin type A (BoNT-A) to treat hyperactive facial muscles. Unexpected side effects of BoNT-A injection may occur because the anatomy of the forehead musculature is not fully characterized. OBJECTIVES: The authors described the lateral border of the frontalis in terms of facial landmarks and reference lines to determine the safest and most effective forehead injection sites for BoNT-A. METHODS: The hemifaces of 49 embalmed adult Korean cadavers were dissected in a morphometric analysis of the frontalis. L2 was defined in terms of FT (the most protruding point of the frontotemporal region), L0 (the line connecting the infraorbital margin with the tragus), and L1 (the line parallel to L0 and passing through FT) such that L2 was positioned 45° from L1 and passed through FT. RESULTS: The distance from FT to the superior margin of the orbicularis oculi was 12.3 ± 3.3 mm. The frontalis extended more than 5 cm along L2 in 49 of 49 cases (100%), more than 6 cm in 47 cases (95.9%), more than 7 cm in 34 cases (69.4%), more than 8 cm in 11 cases (22.4%), and more than 9 cm in 3 cases (6.1%). The lateral border of the frontalis ran parallel to and within 1 cm of the medial side of L2. CONCLUSIONS: Surface anatomy mapping can assist with predicting the lateral border of the frontalis to minimize the side effects and maximize the efficiency of BoNT-A injections into the forehead.

Evidence Suggesting that the Buccal and Zygomatic Branches of the Facial Nerve May Contain Parasympathetic Secretomotor Fibers to the Parotid Gland by Means of Communications from the Auriculotemporal Nerve.

BACKGROUND: The auriculotemporal nerve is one of the peripheral nerves that communicates with the facial nerve. However, the function of these communications is poorly understood. Details of how these communications form and connect with each other are still unclear. In addition, a reliable anatomical landmark for locating these communications during surgery has not been sufficiently described. METHODS: Microdissection was performed on 20 lateral hemifaces of 10 soft-embalmed cadavers to investigate facial-auriculotemporal nerve communications with emphasis on determining their function. The auriculotemporal nerve was identified in the retromandibular space and traced towards its terminations. The communicating branches were followed and the anatomical relationships to surrounding structures observed. RESULTS: The auriculotemporal nerve is suspended above the maxillary artery in the dense retromandibular fascia behind the mandibular ramus. It forms a knot and fans out, providing multiple branches in all directions in the sagittal plane. Inferiorly, it connects the maxillary periarterial plexus, while minute branches supply the temporomandibular joint anteriorly. The larger branches mainly communicate with the branches of the temporofacial division of the facial nerve, and the auricular branches enter the fascia of the auricular cartilage posteriorly. The temporal branches and occasionally the zygomatic branches arise superiorly to distribute within the temporoparietal fascia. The auriculotemporal nerve forms the parotid retromandibular plexus through two types of communication. It sends one to three branches to join the zygomatic and buccal branches of the facial nerve at the branching area of the temporofacial division. It also communicates with the periarterial plexus of the superficial temporal and maxillary arteries. This plexus continues anteriorly along the branches of the facial nerve and the periarterial plexus of the transverse facial artery as the parotid periductal autonomic plexus, supplying the branches of the parotid duct within the loop of the two main divisions of the parotid gland. CONCLUSION: A single cutaneous zygomatic branch arising from the auriculotemporal nerve in some specimens, the intraparotid communications with the zygomatic and the buccal trunks of the facial nerve, the retromandibular communications with the superficial temporal-maxillary periarterial plexuses, and the periductal autonomic plexus between the loop of the two main facial divisions lead to the suggestion that these communications of the auriculotemporal nerve convey the secretomotor to the zygomatic and buccal branches of the facial nerve. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.