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.

Spinal accessory nerve anatomy in the posterior cervical triangle: A systematic review with meta-analysis.

This study aimed to investigate the anatomy of the spinal accessory nerve (SAN) in the posterior cervical triangle, especially in relation to adjacent anatomical landmarks, along with a systematic review of the current literature with a meta-analysis of the data. Overall, 22 cadaveric and three prospective intraoperative studies, with a total of 1346 heminecks, were included in the analysis. The major landmarks relevant to the entry of the SAN at the posterior border of the SCM muscle (PBSCM) were found to be the mastoid apex, the great auricular point (GAP), the nerve point (NP), and the point where the PBSCM meets the upper border of the clavicle. The SAN was reported to enter the posterior cervical triangle above GAP in 100% of cases and above NP in most cases (97.5%). The mean length of the SAN along its course from the entry point to its exit point from the posterior triangle of the neck was 4.07 ± 1.13 cm. The SAN mainly gave off 1 or 2 branches (32.5% and 31%, respectively) and received either no branches or one branch in most cases (58% and 23%, respectively) from the cervical plexus during its course in the posterior cervical triangle. The major landmarks relevant to the entry of the SAN at the anterior border of the TPZ muscle (ABTPZ) were found to be the point where the ABTPZ meets the upper border of the clavicle and the midpoint of the clavicle, along with the mastoid apex, the acromion, and the transverse distance of the SAN exit point to the PBSCM. The results of the present meta-analysis will be helpful to surgeons operating in the posterior cervical triangle, aiding the avoidance of the iatrogenic injury of the SAN.

Sternocleidomastoid Muscle in Fetuses: Classification, Morphometric Analysis, and Clinical Significance.

PURPOSE: This study aimed to examine variations and morphometric properties of the sternocleidomastoid muscle (SCM) in fetuses in terms of infancy and early childhood surgeries. MATERIALS AND METHODS: Neck regions of 27 fetuses (mean age: 23.30±3.40 wk, sex: 11 boys and 16 girls) fixed with 10% formalin were dissected bilaterally. Photographs of the dissected fetuses were taken in the standard position. Morphometric measurements, such as length, width, and angle, were performed on the photographs using the ImageJ software. In addition, the origin and insertion of SCM were detected. Taking into account the studies in the literature, a classification consisting of 10 types associated with the origin of SCM was carried out. RESULTS: No statistically significant difference was observed in the parameters in terms of side and sex ( P >0.05), except from the linear distance between the clavicle and motor point where the accessory nerve enters SCM (20.10±3.76 for male, 17.53±4.05 for female, P =0.022). Two-headed SCM (Type 1) was detected in 42 out of 54 sides. Two-headed clavicular head (Type 2a) was detected on 9 sides, and 3-headed (Type 2b) on 1 side. A 2-headed sternal head (Type 3) was detected on 1 side. A single-headed SCM (Type 5) was also detected on 1 side. CONCLUSION: Knowledge related to variations of the origin and insertion of fetal SCM may be helpful in preventing complications during treatments of pathologies such as congenital muscular torticollis in early period of life. Moreover, the calculated formulas may be useful to estimate the size of SCM in newborns.

The Great Auricular Nerve Trigger Site: Anatomy, Compression Point Topography, and Treatment Options for Headache Pain.

BACKGROUND: Peripheral nerve decompression surgery can effectively address headache pain caused by compression of peripheral nerves of the head and neck. Despite decompression of known trigger sites, there are a subset of patients with trigger sites centered over the postauricular area coursing. The authors hypothesize that these patients experience primary or residual pain caused by compression of the great auricular nerve. METHODS: Anatomical dissections were carried out on 16 formalin-fixed cadaveric heads. Possible points of compression along fascia, muscle, and parotid gland were identified. Ultrasound technology was used to confirm these anatomical findings in a living volunteer. RESULTS: The authors' findings demonstrate that the possible points of compression for the great auricular nerve are at Erb's point (point 1), at the anterior border of the sternocleidomastoid muscle in the dense connective tissue before entry into the parotid gland (point 2), and within its intraparotid course (point 3). The mean topographic measurements were as follows: Erb's point to the mastoid process at 7.32 cm/7.35 (right/left), Erb's point to the angle of the mandible at 6.04 cm/5.89 cm (right/left), and the posterior aspect of the sternocleidomastoid muscle to the mastoid process at 3.88 cm/4.43 cm (right/left). All three possible points of compression could be identified using ultrasound. CONCLUSIONS: This study identified three possible points of compression of the great auricular nerve that could be decompressed with peripheral nerve decompression surgery: Erb's point (point 1), at the anterior border of the sternocleidomastoid muscle (point 2), and within its intraparotid course (point 3).

Trapezius muscle branch of the spinal accessory nerve without penetrating the sternocleidomastoid muscle as a pitfall in neck dissection: prevalence in a Japanese institution and a protocol for the prevention of iatrogenic injury.

BACKGROUND: The spinal accessory nerve (SAN) has several anatomical variations, which may be a pitfall in neck dissection (ND). These include the trapezius muscle branch (TB), which stems from the common trunk before entering the sternocleidomastoid muscle (SCM). AIMS/OBJECTIVES: To investigate the prevalence of this variation and suggest a protocol for preventing unexpected injury of the TB in ND. MATERIALS AND METHODS: We conducted a retrospective cohort study for 93 patients who had undergone neck dissection (117 sides) without resection of the SCM nor SAN. We recorded the division of the TB after and before penetration of the SCM by the common trunk (penetrating type TB [PTB]) and non-penetrating type TB [NPTB], respectively). RESULTS: Among NDs, PTB and NPTB were observed in 61 (52%) and 56 (48%) sides, respectively. In the subgroup of 24 cases with bilateral ND, PTB/PTB, NPTB/NPTB, and NPTB/PTB were observed in eight (33%), nine (38%), and seven (29%) cases, respectively. The prevalence of PTB/NPTB did not differ according to age, sex, or laterality. CONCLUSIONS AND SIGNIFICANCE: NPTB is a common anatomical variation. The presence or absence of a branch from the common trunk must be initially checked to avoid unexpected damage to the TB.

The sternohyoid muscle flap for new dynamic facial reanimation technique: Anatomical study and clinical results.

BACKGROUND: Long-term facial nerve palsy has a highly negative impact on patients' quality of life. In 2016, Alam reported one case of facial reanimation with the sternohyoid muscle after publishing a preclinical study in 2013. Despite the potentially ideal characteristics of this muscle for reanimation of facial palsy, this technique is still not widely used. The objective of our description of cases was to present the clinical results obtained with the surgical procedure and the study on cadavers to confirm the anatomical findings. METHODS: This work describes the anatomical study of the vascular and nervous pedicle of the sternohyoid muscle compared with clinical results from a series of patients with long-term facial paralysis who underwent facial reanimation between June 2016 and September 2019, through the insertion of the sternohyoid muscle into the masseteric nerve. RESULTS: The anatomical study was conducted in eight human hemi-necks. In five cases (62%), the vascular pedicle was provided by the superior thyroid artery, and the entrance of the ansa cervicalis to the muscle was constant 1.8 cm from the distal insertion. This series included ten patients who underwent the surgery technique of facial reanimation using the sternohyoid muscle, with a 90% (n = 9) of reinnervation; 100% (n = 10) of flaps were viable, and none of the patients showed complications in the donor area. CONCLUSIONS: The sternohyoid muscle showed itself as a reliable muscle as a free flap in facial reanimation, and alternative to the gracilis flap. The surgical technique was safe, without any complications, with excellent excursion, recovery, and aesthetic results.

Classification of the patterns of the emerging branches of the superficial cervical plexus / Clasificación de los patrones de las ramas emergentes del plexo cervical superficial

SUMMARY: The cutaneous branches of the superficial cervical plexus (SCP) emerge at variable points, from beneath the posterior margin of the sternocleidomastoid muscle and from this point radiate like "spokes of a wheel" antero-inferiorly and postero-superiorly. This study aimed to classify the emerging points of the branches of the superficial cervical plexus in relation to their location on the sternocleidomastoid muscle. In order to classify the emerging points of the superficial cervical plexus, the sternocleidomastoid muscle was first measured from mastoid process to clavicle; subsequently each branch of the superficial cervical plexus was measured from the mastoid process to their exit points. The emerging points of the superficial cervical plexus branches were classified according to Kim et al. (2002) seven categories: Type I (32 %); Type II (13 %); Type III (35 %); Type IV (13 %); Type V, VI, VII (2 %). The order in which the superficial cervical plexus branches emerged from the posterior margin of the sternocleidomastoid muscle remained constant, i.e. lesser occipital, great auricular, transverse cervical and supraclavicular nerves. Knowledge of emerging points may assist in the effective anaesthesia to all branches of the superficial cervical plexus during surgical procedures of the neck, viz. carotid endarterectomy and thyroid surgery.

RESUMEN: Las ramas cutáneas del plexo cervical superficial (SCP) emergen en puntos variables, desde el margen pos- terior del músculo esternocleidomastoideo y desde este punto inferior irradian como "radios de rueda" anteroinferior y postero-superior. Este estudio tuvo como objetivo clasificar los puntos emergentes de las ramas del plexo cervical superficial en relación a su ubicación en el músculo esternocleidomastoideo. Para clasificar los puntos emergentes del plexo cervical superficial, primero se midió el músculo esternocleidomastoideo desde el proceso mastoides hasta la clavícula; posteriormente se midió cada rama del plexo cervical superficial desde el proceso mastoideo hasta sus puntos de salida. Los puntos emergentes de las ramas del plexo cervical superficial se clasificaron según Kim et al. (2002) en siete categorías: Tipo I (32 %); Tipo II (13 %); Tipo III (35 %); Tipo IV (13 %); Tipo V, VI, VII (2 %). El orden en el que las ramas del plexo cervical superficial emergían del margen posterior del músculo esternocleidomastoideo se mantuvo constante, es decir, los nervios occipital menor, auricular magno, cervical transverso y supraclavicular. El conocimiento de los puntos emergentes puede ayudar a la anestesia eficaz de todas las ramas del plexo cervical superficial durante los procedimientos quirúrgicos del cuello, a saber, endarterectomía carotídea y cirugía de tiroides.

The X-pointer: A forgotten anatomical relationship of spinal accessory nerve and great auricular nerve.

INTRODUCTION: The preservation of the spinal accessory nerve cannot be overlooked in neck dissection. Injury to the nerve results in shoulder dysfunction and other related morbidities. In this article, we describe a unique constant relationship between spinal accessory nerve and great auricular nerve, at the junction of the anterior and posterior triangles of the neck, eponymously labelled the X- pointer. METHODOLOGY: This was an observational study conducted at a tertiary care cancer centre that runs a comprehensive surgical training program. A 100 cases of modified radical neck dissection performed for oral cavity squamous cell carcinoma from January 2017 to January 2019 in were included. The relationship was analyzed in 100 cases of neck dissection for its constancy. RESULT: In all the 100 cases, the X-pointer was demonstrated as a constant anatomical relationship between the spinal accessory nerve and great auricular nerve. The crossing over of the nerve on the undersurface of the sternocleidomastoid muscle is constant and independent of the patient's body proportions. CONCLUSIONS: The relationship between the spinal accessory nerve and great auricular nerve remains constant irrespective of the technique of neck dissection and body habitus of the patient. In our view, this relationship can be used as an additional confirmatory landmark to prevent inadvertent injury to the spinal accessory nerve.

Thyrohyoideus muscle innervation in the horse.

OBJECTIVE: To describe the innervation of the thyrohyoideus (TH) muscle and to confirm our findings with stimulation of first cervical (C1) nerve branches. STUDY DESIGN: Ex vivo phase 1 and clinical phase 2. ANIMALS: Fourteen head and neck specimens and 17 client-owned horses. METHODS: In phase 1, the cranial nerve (CN) XII and the C1 nerve were dissected with their branches in 20 dissections were performed on 14 specimens (6 left and right side and 8 only left or right) Anatomy was noted. Samples of nerve bifurcations were collected for histological confirmation of anatomical findings. First cervical nerve branches were stimulated in horses undergoing cervical nerve graft to treat laryngeal hemiplegia. RESULTS: The nerve innervating the TH muscle arose directly from the C1 nerve in 17 of 20 dissections, from an anastomotic branch between CN XII and the C1 nerve in two of 20 dissections, and from the C1 nerve and the anastomotic branch in one of 20 dissections. No direct connection between the TH muscle and CN XII was found. Histological examination revealed that the anastomosis was composed of C1 nerve fibers passing over to CN XII. First cervical stimulation resulted in TH muscle contraction in 16 of 17 horses. CONCLUSIONS: The innervation of the TH muscle originated from the C1 nerve according to dissection, histological, and conduction studies, with variation in the branching pattern. CLINICAL SIGNIFICANCE: Care should be taken to preserve the C1 nerve during prosthetic laryngoplasty. The surgical technique for C1 nerve grafts should be reconsidered in light of these findings, along with new options to treat dorsal displacement of the soft palate..

Nervio occipital mayor: trayecto, relaciones anatómicas e implicancias clínicas de sus posibles sitios de atrapamiento / Great occipital nerve: course, anatomical relations and clinical implications of their potential entrapment sites

RESUMEN: El nervio occipital mayor (NOM) se forma del ramo dorsal del nervio espinal C2 y asciende entre la musculatura cervical posterior para inervar la piel del cuero cabelludo. Diversos autores han descrito su recorrido, sin embargo, es escasa la información referente a la relación que presenta este nervio con el músculo oblicuo inferior de la cabeza (OIC) y su trayecto intramuscular. El objetivo de este estudio fue determinar el recorrido y relaciones que el NOM estableció en el intervalo existente entre los músculos OIC y músculo trapecio (T). Para ello, se midieron las distancias verticales y horizontales a la altura de la protuberancia occipital externa y línea mediana, y se dividió al músculo OIC en tercios para observar variaciones del recorrido de este nervio. Junto con medir el diámetro del NOM, se midieron las distancias vertical y horizontal de este nervio a través de cinco puntos de referencia muscular y un punto de referencia vascular. Estos puntos musculares fueron: a) sobre el vientre del músculo OIC (punto 1); b) en la cara profunda del músculo semiespinoso de la cabeza (SEC) (punto 2); c) en la cara superficial del músculo SEC (punto 3); d) en la cara profunda del músculo T (punto 4); y e) en la cara superficial del músculo T (punto 5). A este se sumó el punto 6, en el cual se establecieron las distancias vertical y horizontal con la arteria occipital a la altura de la cara superficial del músculo T. Para ello se disecaron 18 cabezas (36 triángulos suboccipitales) de cadáveres adultos brasileños pertenecientes al laboratorio de Anatomía de la Universidade Federal de Alagoas (UFAL), Maceió, Brasil. Las distancias verticales y horizontales obtenidas respecto de los seis puntos fueron: 63,67 y 27,15 mm (punto 1); 53,89 y 21,44 mm (punto 2); 30,61 y 14,49 mm (punto 3); 20,39 y 22,8 mm (punto 4); 5,86 y 33,46 mm (punto 5); 5,99 y 35,56 mm (punto 6), respectivamente. En relación al músculo OIC, el NOM se ubicó en un 72,22 % de las muestras en el tercio medio de este músculo, 19,44% en su tercio lateral y un 8,33 % en su tercio medial. Todos estos hallazgos deben ser considerados al momento de diagnosticar correctamente posibles atrapamientos del NOM en la región cervical profunda, siendo además, una contribución para el éxito de procedimientos quirúrgicos de esta región.

SUMMARY: The great occipital nerve (GON) is formed from the dorsal branch of the C2 spinal nerve and ascends between the posterior cervical musculature to innervate the skin of the scalp. Various authors have described its course, however, there is little information regarding the relationship that this nerve presents with the obliquus capitis inferior (OCI) and its intramuscular path. The objective of this study was to determine the route and relationships that the GON established in the interval between the OCI muscles and the trapezius muscle (T). For this, the vertical and horizontal distances were measured at the height of the external occipital protuberance and median line, and the OCI muscle was divided into thirds to observe variations in the path of this nerve. Along with measuring the diameter of the GON, the vertical and horizontal distances of this nerve were measured through five muscle reference points and one vascular reference point. These muscle points were: a) on the belly of the OCI muscle (point 1); b) in the deep face of the semispinalis capitis muscle (SCM) (point 2); c) on the surface of the SCM (point 3); d) on the deep face of the T (point 4); and e) on the surface face of the T (point 5). To this was added point 6, in which the vertical and horizontal distances were established with the occipital artery at the height of the superficial face of the T. For this, 18 heads (36 suboccipital triangles) of Brazilian adult corpses belonging to the Anatomy laboratory of the Universidade Federal de Alagoas (UFAL), Maceió, Brazil, were dissected. The vertical and horizontal distances obtained with respect to the six points were: 63.67 and 27.15 mm (point 1); 53.89 and 21.44 mm (point 2); 30.61 and 14.49 mm (point 3); 20.39 and 22.8 mm (point 4); 5.86 and 33.46 mm (point 5); 5.99 and 35.56 mm (point 6), respectively. In relation to the OCI, the GON was located in 72.22 % of the samples in the middle third of this muscle, 19.44 % in its lateral third and 8.33 % in its medial third. All these findings should be considered when correctly diagnosing possible entrapments of GON in the deep cervical region, being a contribution to the success of surgical procedures in this region.

Relationship of the lobular branch of the great auricular nerve to the tympanoparotid fascia: Spatial anatomy for salvage during face and neck lift.

To enable selection of a safer suspension site to use in face and neck lifting procedures, the spatial relationship between the tympanoparotid fascia and the great auricular nerve should be clarified. In this study, we aimed to elucidate the position of the tympanoparotid fascia and the pathway of the lobular branch of the great auricular nerve traversing the tympanoparotid fascia. Twenty hemifaces from non-preserved bequeathed Korean cadavers (5 males, 7 females; mean age, 77.0 years) were dissected to determine the great auricular nerve distribution close to the tympanoparotid fascia of clinical significance for face and neck lift procedures. We observed the tympanoparotid fascia in all specimens (20 hemifaces). The tympanoparotid fascia was located anteriorly between the tragus and intertragic notch. Regarding the spatial relationship between the tympanoparotid fascia and the great auricular nerve, we found the sensory nerve entering the tympanoparotid fascia in all specimens (100%), and the depth from the skin was approximately 4.5 mm; in 65% of the specimens, the lobular branch was found to run close to the tympanoparotid fascia before going into the earlobe. Provided with relatively safer surface mapping to access the tympanoparotid fascia free of the lobular branch of the great auricular nerve, surgeons may better protect the lobular branch by anchoring the SMAS-platysma flap and thread to the deeper superior and anterior portions of the expected tympanoparotid fascia.

The Greater Occipital Nerve and Obliquus Capitis Inferior Muscle: Anatomical Interactions and Implications for Occipital Pain Syndromes.

BACKGROUND: The compression/injury of the greater occipital nerve has been identified as a trigger of occipital headaches. Several compression points have been described, but the morphology of the myofascial unit between the greater occipital nerve and the obliquus capitis inferior muscle has not been studied yet. METHODS: Twenty fresh cadaveric heads were dissected, and the greater occipital nerve was tracked from its emergence to its passage around the obliquus capitis inferior. The intersection point between the greater occipital nerve and the obliquus capitis inferior, and the length and thickness of the obliquus capitis inferior, were measured. In addition, the nature of the interaction and whether the nerve passed through the muscle were also noted. RESULTS: All nerves passed either around the muscle loosely (type I), incorporated in the dense superficial muscle fascia (type II), or directly through a myofascial sleeve within the muscle (type III). The obliquus capitis inferior length was 5.60 ± 0.46 cm. The intersection point between the obliquus capitis inferior and the greater occipital nerve was 6.80 ± 0.68 cm caudal to the occiput and 3.56 ± 0.36 cm lateral to the midline. The thickness of the muscle at its intersection with the greater occipital nerve was 1.20 ± 0.25 cm. Loose, tight, and intramuscular connections were found in seven, 31, and two specimens, respectively. CONCLUSIONS: The obliquus capitis inferior remains relatively immobile during traumatic events, like whiplash injuries, placing strain as a tethering point on the greater occipital nerve. Better understanding of the anatomical relationship between the greater occipital nerve and the obliquus capitis inferior can be clinically useful in cases of posttraumatic occipital headaches for diagnostic and operative planning purposes.

Report of a non-looped variant of ansa cervicalis with omohyoid innervation from accessory nerve branch and omohyoid attachment to mastoid process.

INTRODUCTION: A variant of the innervation of the infrahyoid neck musculature is reported in which the typical looped ansa cervicalis structure is absent. In this variant, the infrahyoid muscles (sternohyoid, sternothyroid omohyoid and thyrohyoid) were innervated by a presumptive superior root of "ansa cervicalis" traveling with vagus nerve (CN X) and not branching from hypoglossal nerve (CN XII). The omohyoid muscle, typically innervated by the inferior root of ansa cervicalis, is instead innervated by nerve fibers branching from the accessory nerve (CN XI). This formation created a non-looping variant of ansa cervicalis. Furthermore, the omohyoid muscle did not attach to the hyoid bone but instead attached to the mastoid process of the temporal bone by merging its fibers superiorly and posteriorly with the clavicular portion of the sternocleidomastoid muscle, creating a "sternocleidoomomastoid" muscle innervated by a branch of accessory nerve. MATERIALS AND METHODS: This variation was found in one black male cadaver from a cohort of 25 male and female cadavers. RESULTS: Only one variation of ansa cervicalis was observed. CONCLUSIONS: As neck dissections and surgical procedures of this region are performed for a variety of conditions-including coronary artery bypass grafting and metastatic neck disease-variations of this type are of broad clinical surgical importance.

[Dissection and observation of a large unnamed nerve in the posterior cervical triangle].

OBJECTIVE: To characterize the anatomical features of a large unnamed nerve in the posterior cervical triangle and clarify its relationship with the lesser occipital nerve. METHODS: We dissected 31 adult formalin-fixed cadaver head and neck specimens (62 sides). The lateral cervical region, the anterior cervical region, the sternocleidomastoid region, and the occipital region were dissected to define the anatomical features of the unnamed nerve. RESULTS: This unnamed nerve was identified in the posterior cervical triangle in 96.8% of the specimens. The main trunk of the nerve had a diameter of about 3 mm with a length of around 10 cm. The nerve arose from the anterior branch of the second cervical nerve (C2, C2-3), entered the posterior cervical triangle at 1-3 cm above the accessory nerve, and continued to ascend along or in parallel with the posterior border of the sternocleidomastoid muscle. It passed between the attachments of the sternocleidomastoid and the trapezius to the occiput and divided into 3-5 branches, which innervated the skin area between the lesser and greater occipital nerves. CONCLUSIONS: We identified a large unnamed nerve in the posterior cervical triangle, for which we coined the name "long occipital nerve" based on its unique anatomical features. The discovery of this nerve can be important for local surgery and for diagnosis and treatment of related diseases.

The course of lower cranial nerves within the neck: a cadaveric dissection study.

PURPOSE: To evaluate the course of lower cranial nerves (CNs) within the neck in relation to surrounding structures and anatomic landmarks via a cadaveric dissection study. METHODS: A total of 70 neck dissections (31 bilateral, 8 unilateral) were performed on 39 adult fresh cadavers [mean (SD) age: 38.5 (11.2) years, 29 male, 10 female] to identify the course of lower CNs [spinal accessory nerve (SAN), vagus nerve and hypoglossal nerve] within the neck in relation to surrounding structures [internal jugular vein (IJV), common carotid artery (CCA)] and distance to anatomical landmarks (cricoid cartilage, hyoid bone, digastric muscle). RESULTS: SAN travelled most commonly anterior to IJV (51.4%) at the level of jugular foramen, while travelling lateral to IJV at the post belly of digastric (55.7%) and inferior to digastric muscle (90%) in most neck dissections. Vagus nerve travelled lateral to CCA in majority (94.3%) of dissections, while medial (2.9%), posterolateral (1.4%) and posterior (1.4%) positions were also noted. Average distance of hypoglossal nerve was 27.7 (9.7) mm to carotid bifurcation, 9.3 (3.9) mm to hyoid bone, and 54.7 (18.0) mm to the inferior border of cricoid cartilage. CONCLUSION: In conclusion, our findings indicate that anatomic variations are not rare in the course of lower CNs within the neck in relation to adjacent structures, and awareness of these variations together with knowledge of distance to certain anatomic landmarks may help the surgeon to identify lower CNs during neck surgery and prevent potential nerve injuries.

Surgical Pitfalls in Carotid Endarterectomy: A New Step-By-Step Approach.

Carotid endarterectomy (CEA) is a surgical intervention that may prevent stroke in asymptomatic and symptomatic patients. Our aim was to examine the microsurgical anatomy of carotid artery and other related neurovascular structures to summarize the CEA that is currently applied in ideal conditions. The upper necks of 2 adult cadavers (4 sides) were dissected using ×3 to ×40 magnification. The common carotid artery, external carotid artery (ECA), and internal carotid artery were exposed and examined. The surgical steps of CEA were described using 3-D cadaveric photos and computed tomography angiographic pictures obtained with help of OsiriX imaging software program. Segregating certain neurovascular and muscular structures in the course of CEA significantly increased the exposure. The division of facial vein allowed for internal jugular vein to be mobilized more laterally and dividing the posterior belly of digastric muscle resulted in an additional dorsal exposure of almost 2 cm. Isolating the ansa cervicalis that pulls hypoglossal nerve inferiorly allowed hypoglossal nerve to be released safely medially. The locations of the ECA branches alter depending on their anatomical variations. The hypoglossal nerve, glossopharyngeal nerve, and accessory nerve pierce the fascia of the upper part of the carotid sheath and they are vulnerable to injury because of their distinct courses along the surgical route. Surgical exposure in CEA requires meticulous dissection and detailed knowledge of microsurgical anatomy of the neck region to avoid neurovascular injuries and to determine the necessary surgical maneuvers in cases with neurovascular variations.

Localization of the motor neuron somata of geniohyoid muscle in rat: A horseradish peroxidase study.

The aim of the study was to investigate the location of motor neuron somata of geniohyoid muscle in rat. Nine Sprague-Dawley rats were used in this study. Operations were performed under general anaesthesia. Nembutal sodium, 40 mg per kg intraperitoneally was used for anaesthesia. 0.02 to 0.05 ml of 30% horseradish peroxidase (Sigma Type VI) solution in normal saline was injected into the exposed right geniohyoid muscle. After 48 hr, the animals were fixed by perfusion through left ventricle of heart, first by 100 ml normal saline and then with 500 ml of 1.25% glutaraldehyde and 1% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4, at room temperature, and finally with 500 ml of 10% sucrose in the same buffer at 4°C. The medulla oblongata and first cervical segment of spinal cord were removed, kept in 10% sucrose in above phosphate buffer at 4°C for 24 hr. Thereafter, their serial transverse sections were cut in a cryostat at a thickness of 60 µm. The sections were treated according to tetramethyl benzidine (TMB)-horseradish peroxidase (HRP) method. HRP-labelled neuron somata were observed at the following sites: (a) In ventral part of right main hypoglossal nucleus in upper two-thirds of the closed part of medulla oblongata. (b) In ventrolateral subnucleus of hypoglossal nucleus in lower third of closed part of medulla oblongata. (c) At spinomedullary junction, they were located in dorsomedial part of right ventral grey column; a few were also seen here scattered on right side of central canal and among corticospinal fibres.

A Novel Approach to Identifying the Spinal Accessory Nerve in Surgical Neck Dissection.

Intraoperative identification of the spinal accessory nerve (SAN) is key in reducing nerve injury. This study aims to explore the surgical anatomy of the SAN and 2 landmarks for its identification-the sternocleidomastoid branch of the occipital artery (SBOA) and superior sternocleidomastoid tendon (SST)-to propose a novel method of identifying the SAN during surgical neck dissections. Twelve cadavers underwent bilateral level II-V neck dissection identifying the SAN, SBOA, and SST. Variation was documented and distance between landmarks and the SAN measured. The most common arrangement had the SST most superficially followed by the SBOA and then the SAN. The SAN was 3.63 ± 4.02 mm from the artery and 2.31 ± 1.72 mm from the tendon. A triangle-bordered by the tendon laterally, artery medially, and digastric muscle superiorly-contained the SAN in 95.8% of cases. This relationship translated into a reliable technique to identify the SAN intraoperatively, which has been used successfully in practice.

Immunohistochemical Detection of Motor Endplates in the Long-Term Denervated Muscle.

BACKGROUND: We have demonstrated that the native motor zone (NMZ) within a muscle is an ideal target for performing nerve-muscle-endplate band grafting (NMEG) to restore motor function of a denervated muscle. This study was designed to determine spatiotemporal alterations of the myofibers, motor endplates (MEPs), and axons in the NMZ of long-term denervated muscles for exploring if NMEG-NMZ technique would have the potential for delayed reinnervation. METHODS: Sternomastoid (SM) muscles of adult female Sprague-Dawley rats (n = 21) were experimentally denervated and denervation-induced changes in muscle weight, myofiber size, MEPs, and intramuscular nerve axons were evaluated histomorphometrically and immunohistochemically at the end of 3, 6, and 9 months after denervation. The values obtained from the ipsilateral normal side served as control. RESULTS: The denervated SM muscles exhibited a progressive reduction in muscle weight (38%, 31%, and 19% of the control) and fiber diameter (52%, 40%, and 28% of the control) for 3-, 6-, and 9-month denervation, respectively. The denervated MEPs were still detectable even 9 months after denervation. The mean number of the denervated MEPs was 79%, 65%, and 43% of the control in the 3-, 6-, and 9-month denervated SM, respectively. Degenerated axons in the denervated muscles became fragmented. CONCLUSIONS: Persistence of MEPs in the long-term denervated SM suggests that some surgeries targeting the MEPs such as NMEG-NMZ technique should be effective for delayed reinnervation. However, more work is needed to develop strategies for preservation of muscle mass and MEPs after denervation.

Revisiting the relationship between the submandibular duct, lingual nerve and hypoglossal nerve.

BACKGROUND: The aim of the study was to evaluate the relations between submandibular duct, lingual nerve and hypoglossal nerve for making a reassessment of this area in fresh frozen specimens. Also, the distance between the angle of the mandible and the vertical line drawn from the point where submandibular duct crossed lingual nerve to the base of the mandible was measured to determine a new landmark for neck surgeons. MATERIALS AND METHODS: Fourteen fresh frozen head and neck specimens were dissected and evaluated. A marginal mandibular incision was made from the mastoid process to the chin. RESULTS: In 8 cases, lingual nerve was crossing the submandibular duct superiorly; in 5 cases, lingual nerve was crossing the duct infero-medially and in 1 case it was parallel to the duct. In 1 case, lingual nerve subdivided into anterior and posterior branches. In 2 cases, 2 parallel submandibular ducts were found and the lingual nerve was crossing the upper duct from superior. In 1 case, lingual nerve was crossing the duct infero-medially and then it was subdividing into branches superior to mylohyoid. In 12 cases, the course of hypoglossal nerve was classical. In 1 case, hypoglossal nerve crossed the submandibular duct medially and coursed parallel to the tendon of posterior belly of digastric. And in another case, hypoglossal nerve crossed the inferior branch of submandibular duct medially. The other structures in this area were as usual. CONCLUSIONS: The main factor for reducing nerve damage during surgery is the understanding of the anatomy of this area.