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.

The Anterolateral Approach, Revisited for Benign Jugular Foramen Tumors With Predominant Extracranial Extension: Microsurgical Anatomy and Case Series (SevEN-012).

BACKGROUND AND OBJECTIVES: The anterolateral approach (ALA) enables access to the mid and lower clivus, jugular foramen (JF), craniocervical junction, and cervical spine with added anterior and lateral exposure than the extreme lateral and endoscopic endonasal approach, respectively. We describe the microsurgical anatomy of ALA with cadaveric specimens and report our clinical experience for benign JF tumors with predominant extracranial extension. METHODS: A stepwise and detailed microsurgical neurovascular anatomy of ALA was explored with cadaveric specimens. Then, the clinical results of 7 consecutive patients who underwent ALA for benign JF tumors with predominant extracranial extension were analyzed. RESULTS: A hockey stick skin incision is made along the superior nuchal line to the anterior edge of the sternocleidomastoid muscle (SCM). ALA involves layer-by-layer muscle dissection of SCM, splenius capitis, digastric, longissimus capitis, and superior oblique muscles. The accessory nerve runs beneath SCM and is found at the posterior edge of the digastric muscle. The internal jugular vein (IJV) is lateral to and at the level of the accessory nerve. The occipital artery passes over the longissimus capitis muscle and IJV and into the external carotid artery, which is lateral and superficial to IJV. The internal carotid artery (ICA) is more medial and deeper than external carotid artery and is in the carotid sheath with the vagus nerve and IJV. The hypoglossal and vagus nerves run along the lateral and medial side of ICA, respectively. Prehigh cervical carotid, prejugular, and retrojugular surgical corridors allow deep and extracranial access around JF. In the case series, gross and near-total resections were achieved in 6 (85.7%) patients without newly developed cranial nerve deficits. CONCLUSION: ALA is a traditional and invaluable neurosurgical approach for benign JF tumors with predominant extracranial extension. The anatomic knowledge of ALA increases competency in adding anterior and lateral exposure of extracranial JF.

Glossopharyngeal, Vagus and Accessory Nerves: Anatomy and Pathology.

The glossopharyngeal, vagus, and accessory nerves are discussed in this article, given their intimate anatomical and functional associations. Abnormalities of these lower cranial nerves may be intrinsic or extrinsic due to various disease processes. This article aims to review these nerves' anatomy and demonstrates the imaging aspect of the diseases which most commonly affect them.

The spinal accessory nerve and its entry point into the posterior triangle of the neck.

BACKGROUND: The course of the spinal accessory nerve in the neck is long and superficial rendering it at high risk of injury during procedures performed in the posterior triangle. The majority of spinal accessory nerve injuries are iatrogenic in nature. This is associated with significant morbidity including reduction in shoulder movements, drooping of the shoulder, winging of the scapula and neuropathic pain. Knowledge of the nerve anatomy reduces the risk of intra-operative nerve injury. Traditional teaching describes the point of entry into the posterior triangle as the intersection between the upper and middle third of the posterior border of sternocleidomastoid. The aim of this study was to determine whether this is in fact the case and if so, whether this landmark can reliably be used to identify the spinal accessory nerve in order to improve patient outcomes. MATERIALS AND METHODS: The spinal accessory nerve was identified unilaterally in 26 cadavers. The total length of sternocleidomastoid was measured as well as the length along the posterior border from the inferior aspect of the mastoid process to the point at which the accessory nerve enters the posterior triangle of the neck. These measurements were used to calculate the ratio of the entry point of the nerve into the posterior triangle along the length of the posterior border of sternocleidomastoid from its superior insertion point. The mean ratio was 0.35 with 95% confidence intervals of 0.33 to 0.36. RESULTS AND CONCLUSIONS: Our findings confirm the traditional description of the entry point of the spinal accessory nerve into the posterior triangle of the neck. We describe a so-called 'safe zone' inferior to the midpoint of the posterior border of sternocleidomastoid within which the spinal accessory nerve is unlikely to be found, thereby reducing the risk of iatrogenic injury.

Cranial Nerve Anatomy.

The 12 cranial nerves (CNs) all have important functions. All, except the accessory nerve, arise solely within the cranial vault. We will discuss each CN function along with its entire CN course. The modality of choice for evaluation of the CN itself is typically MRI, however, CT is very important to access the bony foramina and CN boundaries..

Rare anatomical variant of the spinal accessory nerve: case report and comprehensive review.

Historical studies of the anatomy of the spinal accessory nerve (SAN) have reported conflicting results regarding its relationship with the internal jugular vein (IJV). A literature review was undertaken to establish the prevalence of anatomical variations of the SAN encountered during routine neck dissection surgery, in order to increase awareness and reduce morbidity associated with iatrogenic SAN injury. The published literature was analysed by qualitative synthesis and nine articles were yielded following application of the inclusion and exclusion criteria. Incidences of the SAN lateral to the IJV and medial to the IJV ranged from 39.8% to 96.6%, and 2.6% to 57.4%, respectively. Five of the studies reported incidences of the SAN traversing the IJV, which occurred in 0.9% to 2.8% of cases. One study reported an isolated variant of the SAN dividing around the IJV, with a prevalence of 0.5%. We present a case report demonstrating the rare variant of the SAN traversing the IJV. Preoperative identification of rare anatomical association of the SAN and IJV may reduce perioperative injury to vital structures during neck dissection.

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.

Lower cranial nerve syndromes: a review.

The purpose of this paper is to provide a comprehensive review encompassing the syndromes associated with the lower cranial nerves (LCNs). We will discuss the anatomy of some of these syndromes and the historical contributors after whom they were named. The LCNs can be affected individually or in combination, since the cranial nerves at this level share their courses through the jugular foramen and hypoglossal canal and the extracranial spaces. Numerous alterations affecting them have been described in the literature, but much remains to be discovered on this topic. This paper will highlight some of the subtle differences among these syndromes. Symptoms and signs that have localization value for LCN lesions include impaired speech, deglutition, sensory functions, alterations in taste, autonomic dysfunction, neuralgic pain, dysphagia, head or neck pain, cardiac or gastrointestinal compromise, and weakness of the tongue, trapezius, or sternocleidomastoid muscles. To assess the manifestations of LCN lesions correctly, precise knowledge of the anatomy and physiology of the area is required. Treatments currently used for these conditions will also be addressed here. Effective treatments are available in several such cases, but a precondition for complete recovery is a correct and swift diagnosis.

A contextual thematic analysis of the accessory nerve in Scottish historical medical collections of the Royal Colleges of Edinburgh and Glasgow.

INTRODUCTION: The classification of the accessory nerve (CN XI) remains a source of debate; its exact function has not been fully elucidated having also an atypical morphology for a cranial nerve. A better insight into its anatomical and physiological features is of clinical relevance. The aim was to conduct a review of 18th and 19th century books from the Royal Medical/Surgical Colleges in Scotland, United Kingdom. A contextual historical analysis of the depictions and descriptions of the accessory nerve could provide insight into the disparity in the current descriptions. MATERIALS AND METHODS: Online archive catalogues were systematically searched and, during site visits, resources were formally and contextually analyzed, with the information then thematically analyzed. The themes were discussed against a widely known reference textbook of the era. RESULTS: Based on the thematic analysis, the resources were categorized either as practical anatomy books or field-specific anatomy books including neuroanatomy atlases. This intended use, along with the target audience, influenced the scope and detail of information, typically with general anatomy for students in the practical resources, and specialist information in the field-specific resources. The authors' professional background also influenced the way the accessory nerve was described and/or depicted, with surgeons/physicians placing emphasis on the clinical aspects. Content variations could also be attributed to communication restrictions of the era, and associated purchasing costs. CONCLUSIONS: Although scientific advances are nowadays disseminated at a faster pace, actively bridging the gap between anatomical sciences and clinical research is still needed when considering the accessory nerve to further elucidate the mysteries of this structure.

Anatomic Danger Zones of the Head and Neck.

BACKGROUND: Dermatologic procedures require a detailed understanding of surface anatomy to avoid complications. The head and neck region has prominent danger zones including nerves and vasculature that may be at risk during cutaneous surgery. A thorough understanding of these danger zones can help avoid complications that may lead to functional or cosmetic impairment. METHODS: The anatomic literature regarding the course of high-risk structures of the head and neck was reviewed. Structures deemed at risk during dermatologic procedures were included in the analysis. The final analysis focused on branches of the facial nerve, parotid duct, spinal accessory nerve, trigeminal nerve, and the lacrimal system. Anatomical information was compiled regarding each high-risk structure to develop a "danger zone" at which each respective structure is at risk. RESULTS: The danger zone for each structure was compiled based on the review of the literature and depicted in the figures. CONCLUSION: With careful attention to anatomy and the meticulous surgical technique, there is great potential for reduction in surgical injury to danger zones of the head and neck.

Applied anatomy of the suprascapular nerve: a cadaveric study

The suprascapular nerve plays a very important role in the shoulder. Characterization of anatomy is essential to assist surgeons in shoulder surgery. Objectives: This study is to determine further the anatomical characteristics of the SSN regarding origin, pathway, branching and correlations of SSN with some neighboring structures. Thirty specimens taken from 15 fresh cadavers (9 males and 6 females) were dissected and data were recorded. The presences of the motor branches, sensitive branches, some neighboring structures and the correlation between them and the SSN were de-scribed. The distances from the SSN at the suprascapular notch and spinoglenoid notch to some neighboring structures were measured. The SSN arises from the upper trunk of the brachial plexus. The nerve has two motor branches for supraspinatus and infraspinatus muscles and two sensory branches, the superior articular branch for acromioclavicular joint and coracohumeral ligament about 73.3%, the inferior articular branch for the posterior joint capsule about 100%. The average distance from the nerve at the suprascapular notch to the acromion lateral border is 61.4 mm, to the tip of coracoid is 49.5 mm, and to the superior rim of the glenoid is 31.7 mm. The average distance from the nerve at the spinoglenoid notch to the posterior rim of the glenoid is 19.9 mm. This circles the safe distances for shoulder surgeries. This study deter-mines the anatomical characteristics of the SSN and defines the safe zone on the shoulder. It al-lows surgeons to avoid causing the nerve injury and to approach it easily

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In-Depth Look at the Anatomical Relationship of the Lesser Occipital Nerve, Great Auricular Nerve, and Spinal Accessory Nerve and Their Implication in Safety of Operations in the Posterior Triangle of the Neck.

BACKGROUND: Migraine surgery is an increasingly popular treatment option for migraine patients. The lesser occipital nerve is a common trigger point for headache abnormalities, but there is a paucity of research regarding the lesser occipital nerve and its intimate association with the spinal accessory nerve. METHODS: Six cadaver necks were dissected. The lesser occipital, great auricular, and spinal accessory nerves were identified and systematically measured and recorded. These landmarks included the longitudinal axis (vertical line drawn in the posterior), the horizontal axis (defined as a line between the most anterosuperior points of the external auditory canals) and the earlobe. Mean distances and standard deviations were calculated to delineate the relationship between the spinal accessory, lesser occipital, and great auricular nerves. RESULTS: The point of emergence of the spinal accessory nerve was determined to be 7.17 ± 1.15 cm lateral to the y axis and 7.77 ± 1.10 caudal to the x axis. The lesser occipital nerve emerges 7.5 ± 1.31 cm lateral to the y axis and 8.47 ± 1.11 cm caudal to the x axis. The great auricular nerve emerges 8.33 ± 1.31 cm lateral to the y axis and 9.4 ±1.07 cm caudal to the x axis. The decussation of the spinal accessory and the lesser occipital nerves was found to be 7.70 ± 1.16 cm caudal to the x axis and 7.17 ± 1.15 lateral to the y axis. CONCLUSION: Understanding the close relationship between the lesser occipital nerve and spinal accessory nerve in the posterior, lateral neck area is crucial for a safer approach to occipital migraine headaches, occipital neuralgia, and new daily persistent headaches and other reconstructive or cosmetic operations.

Anatomical study of jugular foramen in the neck / Estudo anatômico do forame jugular no pescoço

Abstract Introduction The anatomical complexity of the jugular foramen makes surgical procedures in this region delicate and difficult. Due to the advances in surgical techniques, approaches to the jugular foramen became more frequent, requiring improvement of the knowledge of this region anatomy. Objective To study the anatomy of the jugular foramen, internal jugular vein and glossopharyngeal, vagus and accessory nerves, and to identify the anatomical relationships among these structures in the jugular foramen region and lateral-pharyngeal space. Methods A total of 60 sides of 30 non-embalmed cadavers were examined few hours after death. The diameters of the jugular foramen and its anatomical relationships were analyzed. Results The diameters of the jugular foramen and internal jugular vein were greater on the right side in most studied specimens. The inferior petrosal sinus ended in the internal jugular vein up to 40 mm below the jugular foramen; in 5% of cases. The glossopharyngeal nerve exhibited an intimate anatomical relationship with the styloglossus muscle after exiting the skull, and the vagal nerve had a similar relationship with the hypoglossal nerve. The accessory nerve passed around the internal jugular vein via its anterior wall in 71.7% of cadavers. Conclusion Anatomical variations were found in the dimensions of the jugular foramen and the internal jugular vein, which were larger in size on the right side of most studied bodies; variations also occurred in the trajectory and anatomical relationships of the nerves. The petrosal sinus can join the internal jugular vein below the foramen.

Resumo Introdução A complexidade anatômica do forame jugular torna a realização de procedimentos cirúrgicos nessa região delicada e difícil. Devido aos avanços obtidos nas técnicas cirúrgicas, as abordagens do forame jugular têm sido feitas com maior frequência, o que requer uma melhoria correspondente no conhecimento de sua anatomia. Objetivo Estudar a anatomia do forame jugular, da veia jugular interna e dos nervos glossofaríngeo, vago e acessório, assim como as relações anatômicas entre estas estruturas na região do forame jugular e no espaço parafaríngeo. Método Foram examinados 60 lados de 30 cadáveres frescos algumas horas após a morte. Os diâmetros e suas relações anatômicas foram analisados. Resultados Os diâmetros do forame jugular e da veia jugular interna foram maiores no lado direito na maioria dos espécimes estudados. O seio petroso inferior terminava na veia jugular interna até 40 mm abaixo do forame jugular, em 5% dos casos. O nervo glossofaríngeo exibiu uma relação íntima anatômica com o músculo estiloglosso após a sua saída do crânio e o nervo vago exibiu uma relação semelhante com o nervo hipoglosso. O nervo acessório passou em torno da veia jugular interna via sua parede anterior em 71,7% dos cadáveres. Conclusão Foram encontradas variações anatômicas nas dimensões do forame jugular e da veia jugular interna, que apresentaram tamanhos maiores à direita na maioria dos espécimes estudados; variações também ocorreram na trajetória e nas relações anatômicas dos nervos. O seio petroso pode se unir à veia jugular interna abaixo do forame.

Compartmental Subdivisions of the Jugular Foramen: A Review of the Current Models.

BACKGROUND: At present, no consensus has been reached on the compartmental subdivision of the jugular foramen (JF), which can complicate surgical planning in this area and hinder understanding of foraminal tumor growth patterns. The extradural neural axis compartment (EDNAC) might aid in producing a standardized model in the future. In the present review, we have summarized the models of JF compartmentalization and analyzed how sound they are anatomically. METHODS: The present narrative review identified the key studies and supporting reports that had discussed, referenced, or first presented models of JF compartmentalization. RESULTS: Three intraforaminal components serve as the basis for JF compartmentalization: the fibro-osseous bridge, neurovascular contents, and EDNAC. A total of 4 models have been proposed to date. These include the 2-part (bipartite) models by Hovelacque (1934) and Shapiro (1972) and the 3-part (tripartite) subdivisions by Katsuta (1997) and Bernard (2018). CONCLUSIONS: The bipartite model has been criticized as being oversimplified and lacking surgical validity. However, support for this compartmentation has persisted despite the increasing popularity of the tripartite model. The 3-part subdivision of Bernard can be considered the most anatomically faithful model to date owing to the consideration of the dura and EDNAC. It is important that future studies consider the entire anatomy of the JF, which may generate an anatomically accurate and surgically applicable compartmental model.

Effective botulinum toxin injection guide for treatment of cervical dystonia.

The aim of this study was to elucidate the distribution of the accessory nerve within the sternocleidomastoid muscle (SCM) to aid identifying the optimum sites for botulinum neurotoxin (BoNT) injections and applying chemical neurolysis. Thirty SCM specimens from 15 Korean cadavers were used in this study. Sihler's staining was applied to 10 of the SCM specimens. Transverse lines were drawn in 20 sections to divide the SCM into 10 divisions vertically, and a vertical line was drawn into the medial and lateral halves from the mastoid process to the sternoclavicular joint. The most densely innervated areas were 5/10-6/10 and 6/10-7/10 along the lateral and medial parts of the muscle, respectively. We suggest injecting BoNT in the medial region 6/10-7/10 along the SCM prior to injecting in the lateral region 5/10-6/10 along the muscle to ensure safe and effective treatment. Clin. Anat. 33:192-198, 2020. © 2019 Wiley Periodicals, Inc.

Anatomical study of jugular foramen in the neck.

INTRODUCTION: The anatomical complexity of the jugular foramen makes surgical procedures in this region delicate and difficult. Due to the advances in surgical techniques, approaches to the jugular foramen became more frequent, requiring improvement of the knowledge of this region anatomy. OBJECTIVE: To study the anatomy of the jugular foramen, internal jugular vein and glossopharyngeal, vagus and accessory nerves, and to identify the anatomical relationships among these structures in the jugular foramen region and lateral-pharyngeal space. METHODS: A total of 60 sides of 30 non-embalmed cadavers were examined few hours after death. The diameters of the jugular foramen and its anatomical relationships were analyzed. RESULTS: The diameters of the jugular foramen and internal jugular vein were greater on the right side in most studied specimens. The inferior petrosal sinus ended in the internal jugular vein up to 40mm below the jugular foramen; in 5% of cases. The glossopharyngeal nerve exhibited an intimate anatomical relationship with the styloglossus muscle after exiting the skull, and the vagal nerve had a similar relationship with the hypoglossal nerve. The accessory nerve passed around the internal jugular vein via its anterior wall in 71.7% of cadavers. CONCLUSION: Anatomical variations were found in the dimensions of the jugular foramen and the internal jugular vein, which were larger in size on the right side of most studied bodies; variations also occurred in the trajectory and anatomical relationships of the nerves. The petrosal sinus can join the internal jugular vein below the foramen.

Rectus Capitis Lateralis Muscle: A Cadaveric Study of a Key Surgical Landmark in the Posterior and Lateral Approaches to the Jugular Foramen.

OBJECTIVE: The rectus capitis lateralis (RCL) is a small cervical muscle that arises from the transverse process of C1 and is intimately related to the jugular process and jugular foramen. We describe its morphology, neurovascular relationships, and its utility as one of the key surgical landmarks in approaches to the jugular foramen. METHODS: Eight cadaveric heads were used to perform far-lateral and transmastoid approaches to the jugular foramen. The neurovascular relationships of the RCL were studied. RESULTS: The RCL originates from the transverse process of C1 and inserts onto the jugular process. It can be found in the muscular interval between the posterior belly of the digastric muscle and the superior oblique muscle with the occipital artery coursing between it and the posterior belly of the digastric muscle. It lies directly posterior to the internal jugular vein and cranial nerves (CNs) IX-XI as they exit the jugular foramen. The vertebral artery courses medially to the RCL as it exits foramen transversarium of C1. As the facial nerve exits the stylomastoid foramen, it is anterolateral to the RCL before turning to enter the parotid gland. The CN XII is seen between the RCL and the occipital condyle from a posterior view. CONCLUSIONS: The RCL usually is preserved unless jugular process needs to be removed to expose the jugular foramen. The RCL is an important surgical landmark for the early identification of the vertebral artery, internal jugular vein, facial nerve, and CNs IX-XII in approaches to the jugular foramen.

Surgical "Safe Zone": Rapid Anatomical Identification of the Lesser Occipital Nerve.

BACKGROUND: Surgical intervention has established a vital role in the management of chronic headaches. The lesser occipital nerve (LON) is a common target in patients suffering from occipital neuralgia and is often resected as a first-line option. We endeavored to define the relationships of the LON in the posterolateral neck to facilitate its safe and rapid intraoperative identification. METHODS: Seven fresh cadavers (14 nerves) were dissected, and their relationships to the mastoid prominence and nearby spinal accessory nerve (SAN) and greater auricular nerve were noted. RESULTS: The distance from the mastoid to the emergence of the LON along the posterior sternocleidomastoid ranged from 36 to 51 mm (mean: 45.2 mm), with relative symmetry between the two nerves in the same cadaver. The SAN emerged an average of 54 mm from the mastoid prominence. CONCLUSION: Exploration for the LON should begin at a point 40 mm from the mastoid prominence along the posterior border of the sternocleidomastoid muscle. If the point of exit of the LON is not identified within 10 mm of this exposure, our dissection continues cranially along the posterior border of the sternocleidomastoid, anterior to the trapezius. In rare cases the nerve may pierce the fibers of the muscle and ascend directly on top of the muscle belly. By limiting the caudal extend of the dissection, we can avoid exposure of the SAN and minimize the risk of iatrogenic nerve injury.

Spinal Accessory Motor Neurons in the Mouse: A Special Type of Branchial Motor Neuron?

The spinal accessory nerve arises from motor neurons in the upper cervical spinal cord. The axons of these motor neurons exit dorsal to the ligamentum denticulatum and form the spinal accessory nerve. The nerve ascends in the spinal subarachnoid space to enter the posterior cranial fossa through the foramen magnum. The spinal accessory nerve then turns caudally to exit through the jugular foramen alongside the vagus and glossopharyngeal nerves, and then travels to supply the sternomastoid and trapezius muscles in the neck. The unusual course of the spinal accessory nerve has long prompted speculation that it is not a typical spinal motor nerve and that it might represent a caudal remnant of the branchial motor system. Our cell lineage tracing data, combined with images from public databases, show that the spinal accessory motor neurons in the mouse transiently express Phox2b, a transcription factor that is required for development of brain stem branchial motor nuclei. While this is strong prima facie evidence that the spinal accessory motor neurons should be classified as branchial motor, the evolutionary history of these motor neurons in anamniote vertebrates suggests that they may be considered to be an atypical branchial group that possesses both branchial and somatic characteristics. Anat Rec, 302:505-511, 2019. © 2018 Wiley Periodicals, Inc.