Anatomy of the Buccal Space: Surgical and Radiological Perspectives.

Among the anatomical spaces in the head and neck area, the buccal space has often been studied in dental/oral surgery and cosmetic surgery because it contains the facial vessels, mandibular and facial nerves, and adipose tissue called the buccal fat pad. In addition, as the space can communicate with other spaces, it can be significant in infections. Although the anatomy of the buccal space has been reported in several studies, there have been discrepancies concerning its boundaries, and its communications have often been overlooked. The aim of this review is to examine the anatomy of buccal space including its boundaries, contents, continuity with adjacent spaces, and clinical significance. A literature review was performed on Google Scholar and PubMed. The literature has depicted the anterior, medial, and lateral boundaries more or less consistently, but descriptions of the posterior, superior, and inferior borders are controversial. The buccal space includes the facial arteries, veins, facial nerves, parotid duct, and lymph nodes, which can be described differently depending on definitions and the extent of the space. As it communicates with other anatomical spaces including the masticatory space, it can be a reservoir and a channel for infections and tumors. Buccal fat pads have various clinical applications, from a candidate for flap reconstruction to a target for removal for cosmetic purposes. This review will help understand the anatomy of the buccal space including its boundaries, residing structures, and communication with other spaces from surgical and radiological perspectives.

Study of Topography of Stylomastoid Foramen With Respect to Nearby Landmarks to Carry Out Facial Nerve Block With Minimum Complications.

Nadbath facial nerve block is the most common procedure to anesthetize the facial nerve at stylomastoid foramen in intraocular surgeries, but it is associated with complications. Also, this foramen exhibits ethnic and racial variations with regard to its location. There is scanty literature describing the topographical location of this foramen. So, the study is carried out. The purpose of the study is to describe the topography of stylomastoid foramen from the surrounding landmarks so that Nadbath facial nerve block can be performed with minimum complications. The study was conducted using 80 adult dry skulls of unknown age and sex, and the distance of this foramen was measured from the tip, upper end, and lower end of the anterior border of the mastoid process and jugular foramen. The statistical analysis consisting of mean, SD, median, range mode, and t test was calculated. Mean distances of stylomastoid foramen from the upper end, the lower end of anterior border and tip of mastoid process and jugular foramen on right side were 1.5±0.16, 1.02±0.09, 0.84±0.09, and 0.49±0.06 cm and those on left side were 1.5±0.16, 1.02±0.09, 0.84±0.09, and 0.5±0.06 cm, respectively. The mode of these distances was 1.5, 1, 0.8, and 0.5, both on the right and left sides. The topographic information about stylomastoid foramen given in this study is useful to anesthetists to carry out Nadbath facial nerve block successfully with minimum complications.

Nerve to the zygomaticus major muscle: An anatomical study and surgical application to smile reconstruction.

Smile reconstruction using the branches that supply the zygomaticus major muscle as a motor source is an established procedure in facial reanimation surgery for facial paralysis. However, the anatomy of the nerve to the muscle remains unclear. Therefore, we herein examined the topographical anatomy of the nerve to the zygomaticus major muscle to obtain more detailed information on donor nerve anatomy. Preserved cadaver dissection was performed under a microscope on 13 hemifaces of 8 specimens. The branches that innervate the zygomaticus major muscle and their peripheral routes medial to the muscle were traced and examined. A median of four (ranges 2-4) branches innervated the zygomaticus major muscle. The proximal two branches (near the muscle origin) arose from the zygomatic branch, the second of which was the major branch. The distal branches (near the oral commissure) arose from the buccal branch or zygomaticobuccal plexus. The vertical distance from the caudal margin of the zygomatic arch to the major branch intersecting point was 19 ± 4.0 mm, while the horizontal distance parallel to the Frankfort plane was 29 ± 5.2 mm. The proximal two branches innervating the zygomaticus major muscle were detected in the majority of specimens. The anatomical findings obtained herein on the nerve to the zygomaticus major muscle will allow for more reliable donor selection in facial reanimation surgery.

3D 4K Exo-Endoscopic Temporal Bone Dissection: A Novel Approach for Sharing the Anatomy.

BACKGROUND: Temporal bone dissection is overwide recognized as an ideal training method for otologic surgeons. The knowledge of temporal bone anatomy and especially of the course of infratemporal facial nerve is pivotal in practice. The 3D exoscope is an innovative and promising tool, that was recently introduced in ear surgery. METHODS: A high-definition 3D exoscope (3D VITOM®) mounted on the VERSACRANETM holding system (Karl Storz) was used to perform two temporal bone dissection, with the aim to study the anatomy of infratemporal facial nerve. The 3D endoscope (TIPCAM®1 S 3D ORL, Karl Storz) was used in combination to provide a close-up high-quality view and to provide a different angle of view on fine anatomical relationships. RESULTS: The high-definition 3D exoscope allowed to conduct the dissection with high quality visualization and to share the same surgical field with trainees. Moreover, it showed a high interchangeability with the 3D endoscope. CONCLUSIONS: 3D 4 K Exo-endoscopic temporal bone dissection seems to have benefits in terms of educational purpose, especially concerning anatomy understanding. The superiority in teaching value of this tool should be further investigated in cohort studies.

An evaluation of morphometry and dehiscence of facial canal: a systematic review and meta-analysis of observational studies.

INTRODUCTION: The facial canal (FC) is an extensive bony canal that houses the facial nerve and occupies a central position in the petrous part of temporal bone. It is of utmost significance to otologists due to its dehiscence and relationship to the inner or middle ear components. The main objectives of current investigation are to detect variations in the reported values ​​of FC anatomy that may occur due to different methodology and to elucidate the influence of age and ethnic factors on the morphological features of FC. METHODS: The methodology is adapted to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Pooled weighted estimation was performed to calculate the mean length, angle, and prevalence of dehiscence. RESULTS: The cross-sectional shape of FC varied from circular to ellipsoid index and is 1.45 [95% CI, 0.86-2.6]. The mean length of the FC is 34.42 mm [95% CI, 27.62-40.13 mm] and the mean width or diameter is 1.35 mm [95% CI, 1.013-1.63 mm]. The length of the FC in fetuses and children is 21.79 mm [95% CI, 18.44-25.15 mm], and 26.92 mm [95% CI, 23.3-28.3 mm], respectively. In meta-regression, age is observed as a predictor and accounts for 36% of the heterogeneity. The prevalence of FC dehiscence in healthy temporal bones is 29% [95% CI, 20-40%]. CONCLUSION: The different segments of the FC exhibit significant variability and an unusually high incidence of dehiscence, which could potentially have clinical implications for the etiopathogenesis of facial nerve dysfunction.

Radiologic evaluation of the internal carotid artery and jugular bulb in lateral temporal bone resection using 3D computed tomography.

PURPOSE: This study investigated the internal carotid artery (ICA) and jugular bulb (JB) structures in terms of lateral temporal bone resection using 3D computed tomography (CT). METHODS: We retrospectively investigated 80 ears of 40 patients using 3D reconstruction data from normal temporal bone CT. Ten critical points (P) in the temporal bone were marked in the 3D object with reference to the axial, coronal, and sagittal images of the CT scans. An imaginary plane of the facial nerve (PLf) course was also reconstructed in relation to the three points of the chorda-facial junction, P5 (second genu), and P3 (cochleariform) process. RESULTS: The distances (mean ± SD; mm) from points P3 to P1 (the highest level of the JB) and P2 (the posterior wall of the ascending petrous IAC at the level of the Eustachian tube) were 12.03 ± 2.56 and 9.79 ± 1.78, respectively. The distances from point P4 (chorda-facial junction) to P1 and P2 were 10.98 ± 2.70 and 17.66 ± 2.26, respectively. The angles (mean ± SD; degree) between the PLf to the line from Pa (point of the anterior bony canal) to P3 and P4 were 17.80 ± 10.05º and 8.93 ± 5.37º, respectively. The angles between the PLf to the line from P3 to P1 and P2 were - 36.35 ± 13.28º and - 24.78 ± 13.91º, respectively. The angles between the PLf to the line from P4 to P1 and P2 respectively were - 40.35 ± 15.37º and - 13.34 ± 7.63º. CONCLUSIONS: Understanding the anatomical relationships of P1 and P2 at P3 and P4 can be helpful in preventing iatrogenic trauma of the ICA and JB.

Anatomical Insights on the Cervical Nerve for Contemporary Face and Neck Lifting: A Cadaveric Study.

BACKGROUND: Despite the significant roles it plays in the functions of the platysma and lower lip, the cervical branch of the facial nerve is often overlooked compared to other branches, but its consideration is critical for ensuring the safety of neck surgeries. OBJECTIVES: The aim of this study was to clarify the anatomical discrepancies associated with the cervical branch of the facial nerve to enhance surgical safety. METHODS: The study utilized 20 fresh-frozen hemiheads. A 2-stage surgical procedure was employed, beginning with an initial deep-plane facelift including extensive neck dissection, followed by a superficial parotidectomy on fresh-frozen cadavers. This approach allowed for a thorough exploration and mapping of the cervical nerve in relation to its surrounding anatomical structures. RESULTS: Upon exiting the parotid gland, the cervical nerve consistently traveled beneath the investing layer of the deep cervical fascia for a brief distance, traversing the deep fascia to travel within the areolar connective tissue before terminating anteriorly in the platysma muscle. A single branch was observed in 2 cases, while 2 branches were noted in 18 cases. CONCLUSIONS: The cervical nerve's relatively deeper position below the mandible's angle facilitates a safer subplatysmal dissection via a lateral approach for the release of the cervical retaining ligaments. Due to the absence of a protective barrier, the nerve is more susceptible to injuries from direct trauma or thermal damage caused by electrocautery, especially during median approaches.

Surgical Anatomy for Asian facial Contouring: A Personal Perspective.

This paper introduces my personal perspective on anatomic structures for reduction malarplasty, mandibular contouring surgery, and masseter muscle resection. The zygomaticofacial nerve innervates a rectangular area, and each side measures 18.8±4 and 15.8±3.4 mm. The center of the rectangle is located laterally, at 17.3±5.5 mm from the lateral canthus, and then inferiorly, at 18.1±3.1 mm. The point of the zygomaticotemporal nerve appears at the margin of the zygomatic bone, 11.29±2.65 mm below the zygomaticofrontal suture and 21.76±2.76 mm from the superior border of the zygomatic arch. The inferior alveolar nerve in the mandibular canal runs above the lower one-third of the mandibular body. The terminal mandibular canal is located at an average of 4.5 mm under the mental foramen, advances 5.0 mm anteriorly, loops, and ends at the foramen. The facial nerve trunk is located 11 to 14 mm medial to the posterior border of the mandible. The trunk emerges out of the stylomastoid foramen and runs anteroinferiorly at an angle of 45°. The deep branch of the middle masseteric artery travels deep in the muscle, close to the periosteum of the mandible in 94% of cases. The average diameter is 1.23±0.26 mm. The masseteric nerve runs anteriorly and inferiorly between the deep and the middle layers of the masseter. It is observed at 33±5.6 mm from the inferior border of the muscle on the anterior third vertical line of the masseter muscle and at 47±5.5 mm in the posterior third.

Examination of sinus tympani, subtympanic sinus, and facial sinus with MicroCT.

This study aimed to determine sinus tympani, subtympanic sinus (STS), facial sinus (FS) morphologies, and type distributions. Type distributions were based on their relations with the facial nerve (FN). A total of 20 right and 20 left temporal dry bones without physical deformation were scanned with a MicroCT device. All measurements were made using MicroCT programs from sections in the axial plane. For the FS, the average depth was measured as 3.485 mm without any classification, and 29 of the 40 bones had Type C radiological morphology. The mean depth for all sinus tympanicus was 2.646 mm, and 22 of the 40 bones had Type B morphology. For the STS, 29 out of 40 samples had no contact with the FN; regardless of the classification, the average depth was measured as 2.376 mm. We reveal the depths of the tympanic cavities and their relationship with the FN. The results of this study may benefit clinicians performing retrotympanum surgeries.

Delineation and histological examination of the intramuscular innervation of the platysma: Application to botulinum neurotoxin injection.

This study aimed to identify the whole innervation pattern of the platysma using the Sihler's staining, and the axonal composition profile of the sensory-motor anastomosis identified by immunofluorescence assays. The findings provide a comprehensive understanding of the neural anatomy of the platysma and facilitate efficient and safe manipulation for neurotoxin injection. Ten fixed and two fresh hemifaces were included in this study. Sihler's staining was used to the study 10 fixed hemifaces and two fresh hemifaces were used for immunofluorescence assays. In all cases, the cervical branch of facial nerve (Cbr) broadly innervated the platysma, and the marginal mandibular branch of facial nerve (MMbr) provided supplementary innervation to the uppermost part of the platysma. The transverse cervical nerve (TCN), great auricular nerve (GAN), and supraclavicular nerve (SCN) were observed in the lower half of the platysma. In 30% of all cases, there was a communicating loop between the Cbr and TCN. In 20% of all the cases, a communicating branch joined between the Cbr and GAN. For successful esthetic rejuvenation procedures, a clinician should consider the Cbr distribution to the overall platysma and additionally innervation by individual nerves (MMbr, GAN, TCN, and SCN) to the middle and lower portions of the platysma muscle.

Discerning a smile - The intricacies of analysis of post-neck dissection asymmetry.

INTRODUCTION: Iatrogenic facial nerve palsy is distressing to the patient and clinician. The deformity is aesthetically displeasing, and can be functionality problematic for oral competence, dental lip trauma and speech. Furthermore such injuries have litigation implications. Marginal mandibular nerve (MMN) palsy causes an obvious asymmetrical smile. MMN is at particular risk during procedures such as rhytidoplasties, mandibular fracture, tumour resection and neck dissections. Cited causes for the high incidence are large anatomical variations, unreliable landmarks, an exposed neural course and tumour grade or nodal involvement dictating requisite nerve sacrifice. An alternative cause for post-operative asymmetry is damage to the cervical branch of the facial nerve or platysmal dysfunction due to its division. The later tends to have a transient course and recovers. Distinction between MMN palsy and palsy of the cervical branch of the facial nerve or platysma division should therefore be made. In 1979 Ellenbogen differentiated between MMN palsy and "Pseudo-paralysis of the mandibular branch of the facial nerve". Despite this, there is paucity in the literature & confusion amongst clinicians in distinguishing between these palsies, and there is little regarding these post-operative sequelae and neck dissections. METHOD: This article reflects on the surgical anatomy of the MMN and cervical nerve in relation to danger zones during lymphadenectomy. The authors review the anatomy of the smile. Finally, case studies are utilised to evaluate the differences between MMN palsy and its pseudo-palsy to allow clinical differentiation. CONCLUSION: Here we present a simple method for clinical differentiation between these two prognostically different injuries, allowing appropriate reassurance, ongoing therapy & management.

Decompression of the geniculate ganglion and labyrinthine segments of the facial nerve through a middle cranial fossa approach using an ultrasonic surgical system: an anatomic study.

PURPOSE: The aim of this study is to evaluate the feasibility and the safety of a novel, alternative method for bone tissue management in facial nerve decompression by a middle cranial fossa approach. Several applications of Piezosurgery technology have been described, and the technique has recently been extended to otologic surgery. The piezoelectric device is a bone dissector which, using micro-vibration, preserves the anatomic integrity of soft tissue thanks to a selective action on mineralized tissue. METHODS: An anatomic dissection study was conducted on fresh-frozen adult cadaveric heads. Facial nerve decompression was performed by a middle cranial fossa approach in all specimens using the piezoelectric device under a surgical 3D exoscope visualization. After the procedures, the temporal bones were examined for evidence of any injury to the facial nerve or the cochleovestibular organs. RESULTS: In all cases, it was possible to perform a safe dissection of the greater petrosal superficial nerve, the geniculate ganglion, and the labyrinthine tract of the facial nerve. No cases of semicircular canal, cochlea, or nerve damage were observed. All of the dissections were carried out with the ultrasonic device without the necessity to replace it with an otological drill. CONCLUSION: From this preliminary study, surgical decompression of the facial nerve via the middle cranial fossa approach using Piezosurgery seems to be a safe and feasible procedure. Further cadaveric training is recommended before intraoperative use, and a wider case series is required to make a comparison with conventional devices.

Communicating Branches of the Facial Nerve: Descriptions and Clinical Considerations.

BACKGROUND: Major branching patterns of the facial nerve have been extensively studied because damage to branches of the nerve is associated with complications ranging from weakness to paralysis. However, communicating branches of the facial nerve have received far less attention despite being hypothesized as a means of motor recovery following facial nerve injury. OBJECTIVES: The aim of this study was to characterize the frequency of communicating branches of the facial nerve to provide clarity on their anatomy and clinical correlations. METHODS: Bilateral facial dissections were completed on cadaveric donors (n = 20) to characterize the frequency and location of communicating branches across terminal branches of the facial nerve. Statistical analyses were employed to analyze differences between the location of communications by side and whether the communicating branches were more likely to occur on the left or right side (P < 0.05). RESULTS: Communicating branches were identified among all terminal branches of the facial nerve and their frequencies reported. The highest frequencies of communicating branches were identified between the buccal-to-marginal mandibular and zygomatic-to-buccal branches, at 67.5% (27 comm/40 hemifaces). The second highest frequency was identified between the temporal-to-zygomatic branches in 62.5% (25/40) of donors. The marginal mandibular-to-cervical branches had communicating branches at a frequency of 55% (22/40). Location or sidedness of communicating branches did not significantly differ. CONCLUSIONS: Our characterization more accurately defines generalizable areas in which communicating branches are located. These locations of branches, described in relation to nearby landmarks, are fundamental for clinical and surgical settings to improve procedural awareness.

Cadaveric Study of Topographic Anatomy of Temporal and Marginal Mandibular Branches of the Facial Nerve in Relation to Temporomandibular Joint Surgery.

PURPOSE: Detailed anatomy of the facial nerve, including the variations among different ethnic groups, is essential to prevent an iatrogenic injury. The purpose of the study was to document topographic anatomy of temporal and marginal mandibular (MM) branches of the facial nerve in relation to temporomandibular joint (TMJ) surgery. The specific aim was to demonstrate detailed course of temporal and MM nerves, their surgical implications, and to compare the results obtained with the previous studies. METHODS: The investigators implemented a prospective cadaveric study. A dissection was carried out on 52 facial halves. The facial nerve was dissected according to the instructions described in the Cunningham's dissection manual. Anatomic landmarks were selected as determined by Al-Kayat and Bramley, and results obtained were compared with previous published articles. RESULTS: The study sample was composed of 52 facial halves (males, n = 35; females, n = 17). The number of branches of temporal nerve varied in dissected facial halves from 3 (n = 37 [70%]), 2 (n = 14 [26%]), to 1 (n = 1 [2%]). The distance between the lowest concavity of the bony external auditory meatus to the point at which the facial nerve bifurcates (distance B) was considerably less in the study population (1.79 cm) when compared with the reported literature (2.3 cm). There was no significant influence of gender and cephalic index on distances measured. There was 1 branch in 15% of the dissected facial halves (1 in 52) and 2 branches in 85% (44 of 52). The MM nerve was seen coursing below the inferior border of the mandible, and in 44 (85%), the nerve was present above the inferior border of mandible all along the course. CONCLUSIONS: The topographic anatomy of the temporal and MM nerves is the same as reported in the literature. The only considerable difference was found in distance B; hence, surgical procedures involving the distance B require special consideration.

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

PURPOSE: Surgical shortening of the styloid process (SP) mainly involves intraoral and transcervical approaches. A retroauricular incision was performed by our surgical team in endoscope-assisted shortening of the SP. This study aimed to clarify the important anatomic landmarks and adjacent structures around the SP through a retroauricular approach. METHODS: Fifteen fresh corpses (30 sides) were dissected via a retroauricular approach, and indexes were measured. RESULTS: The great auricular nerve (GAN) was divided into the anterior ear branch, lobe branch, and posterior ear branch. The distance from the branch of the GAN to the root of the ear lobe was 21.96 ± 2.55 mm. In the space around the SP, the vertical distance from the junction of the diabetic posterior belly and the mastoid tip to the SP was found to be 12.29 ± 2.46 mm, with a total distance between the skin in front of the mastoid and the facial nerve of 21.63 ± 3.27 mm. The distance between the facial nerve across the SP and the root of the SP was 11.93 ± 2.32 mm. CONCLUSIONS: The retroauricular incision starts from the level of the notch between the tragus and extends backward in an arc to avoid injury to the retroauricular branch of the GAN. The posterior fascia of the parotid gland and the leading edge of the sternocleidomastoid muscle, posterior belly of the digastric muscle, and styloid hyoid muscle are regarded as landmarks for the SP.

Safe Zone for Dissection in Frontotemporal Region to Avoid Injury to the Temporal Branch of Facial Nerve.

ABSTRACT: The objective of this study is to provide a reliable roadmap for temporal branch of the facial nerve, in order to minimize, the risk of injury to the nerve during surgical dissections. A literature search was conducted on temporal branch of facial nerve. The date search range was 1950 to 2017. Databases searched included Medline, Web of science, Biosis, SciELO, Data Citation, and Zoologic Records. Data were collected on, author specialty, date of publication, and the relationship of the temporal branch of facial nerve to various landmarks in the frontotemporal region reported in human anatomic studies. Among the 48 studies reviewed, a total of 3477 anatomic dissections were performed in the craniofacial region. Temporal branch of facial nerve was located between 2.5 and 3 cm from lateral orbital rim. In relation to the zygomatic arch, it was found anywhere from the midpoint of the arch to 1 finger breath posterior to the arch. For the plane, it was most commonly described as being under the superficial temporal fascia (STF) or within the loose areolar tissue. Most anatomic dissections found 2 to 4 twigs of the temporal branch of facial nerve. In relation to the lateral canthus, it was found to be 2.85 +/- 0.69 cm superior and 2.54 +/- 0.43 cm lateral to the lateral canthus. Our study suggests consolidated data on surgical landmarks in order to ensure safe dissection in temporal region and prevent injury to the temporal branch of facial nerve.

Feasibility of Using Posterior Auricular Artery as Landmark for Identification of Facial Nerve Trunk in Parotid Surgery: A Cadaver Study.

INTRODUCTION: Despite good surgical knowledge of the anatomy of parotid gland and meticulous surgical technique, the incidence of facial palsy in parotid surgeries is up to 26.7% transient and 1.7% complete facial palsy(1). The risk of facial palsy increases further in malignant and revision cases. METHOD: Superficial parotidectomy was done in 14 cadaveric hemi faces in 10 cadavers. Posterior auricular artery and its stylomastoid branch was dissected and facial nerve trunk was identified in all cases. The relationship of posterior auricular artery along with its stylomastoid branch with the facial nerve trunk was studied and recorded. RESULT: Posterior auricular artery was found running inferior to the facial nerve trunk in 12 cadaveric dissection while the posterior auricular artery was found crossing below the main trunk of facial in 2 cadaver dissection. The average distance between PAA and facial nerve trunk was 7 mm (2-14 mm) Stylomastoid artery was found arising from Posterior auricular artery in 12 of 14 and it was found running medial to the facial nerve trunk in all the 8 cadavers. CONCLUSION: Post auricular artery can be used as another landmark for identification of the main trunk of facial nerve in parotid surgeries.

The Anatomy of the Temporal and Zygomatic Branches of the Facial Nerve: Application to Crow's Feet Wrinkles.

BACKGROUND: Advances in the understanding of wrinkling crow's feet while improving the safety and efficacy of botulinum toxin type A injection has pointed to drug dispersion in the lateral orbital wrinkles as a cause of adverse events of botulinum toxin type A injection. The purpose of this study is to identify the distribution of temporal and zygomatic branches of facial nerve in the orbicularis oculi muscles. METHODS: Anatomical dissection of cadavers was performed in 31 cadavers, 13 females and 18 males, with ages ranging from 20 to 60 years, which of all had been embalmed by 10% formalin solution. The facial nerve was identified within subcutaneous tissue close periorbital region and both traced proximal and distal. Its temporal branch, zygomatic branch, facial and muscular entrance were located and accurately measured relative to established surface landmarks. RESULTS: Dissection of the facial nerve revealed 2 to 6 entrances of the temporal branch into the orbicularis oculi and 1 to 5 entrances of the zygomatic branch into the orbicularis oculi. Concerning the measurements of neural entering points, distance and angle from orbicularis oculi muscle to lateral ocular angle, a distribution map of its muscular entrance and their patterns of distribution were constructed. According to the dense area of the coordinate map, there were 3 points determined as the muscular entrance points to established surface landmarks. CONCLUSIONS: An anatomical dissection of cadavers was performed to identify the distribution of temporal and zygomatic branches of the facial nerve in the orbicularis oculi. According to the dense area of the coordinate map, the surface landmarks of 3 points were established as the muscular entrance of the facial nerve (MEF).

Microsurgical anatomy of the facial nerve.

The facial nerve connections and pathways from the cortex to the brainstem are intricate and complicated. The extra-axial part of the facial nerve leaves the lateral part of the pontomedullary sulcus and enters the temporal bone through the internal acoustic meatus. In the temporal bone, the facial nerve branches into fibers innervating the glands and tongue. After it emerges from the temporal bone it supplies various facial muscles. It contains a motor, general sensory, special sensory, and autonomic components. The physician needs comprehensive knowledge of the anatomy and courses of the facial nerve to diagnose and treat lesions and diseases of it so that surgical complications due to facial nerve injury can be avoided. This review describes the microsurgical anatomy of the facial nerve and illustrates its anatomy in relation to the surrounding bone, connective, and neurovascular structures.

Wide distribution of central myelin segment along the facial nerve might explain hemifacial spasm with distal nerve compression.

INTRODUCTION: Many researchers have assumed that neurovascular compression of the facial nerve at the site covered by central myelin sheath causes hemifacial spasm. However, some cases do not correspond to this hypothesis. The aim of this study was to clarify the myelin histology in the facial nerve. MATERIALS AND METHODS: Histological analyses were conducted on 134 facial nerves from 67 cadavers. Three dimensions were measured in these sections: the length from the upper border of the medullopontine sulcus to the boundary between the central and peripheral myelin sheath along the anterior side; the length from the detachment point of the brain stem to the boundary along the posterior side; and the length of the transitional zone (TZ), known as the Obersteiner-Redlich zone. RESULTS: Of the 134 facial nerves, 41 were available for study. The length of the central myelin segment ranged from 4.62 to 12.6 mm (mean 8.06 mm; median 7.98 mm) along the anterior side and from 0.00 to 4.58 mm (mean 1.68 mm; median 1.42 mm) along the posterior side of the facial nerve, and the length of the TZ ranged from 0.00 to 2.76 mm (mean 1.51 mm; median 1.42 mm). CONCLUSIONS: In this study, the length of the central myelin segment in the facial nerve was found to be longer than that previously reported.