Morphological characteristics of the cranial root of the accessory nerve

There has been the controversy surrounding the cranial root (CR) of the accessory nerve. This study was performed to clarify the morphological characteristics of the CR in the cranial cavity. Fifty sides of 25 adult cadaver heads were used. The accessory nerve was easily distinguished from the vagus nerve by the dura mater in the jugular foramen in 80% of 50 specimens. The trunk of the accessory nerve from the spinal cord penetrated the dura mater at various distances before entering the jugular foramen. In 20% of the specimens there was no dural boundary. In these cases, the uppermost cranial rootlet of the accessory nerve could be identified by removing the dura mater around the jugular foramen where it joined to the trunk of the accessory nerve at the superior vagal ganglion. The cranial rootlet was formed by union of two to four short filaments emerging from the medulla oblongata (66%) and emerged single, without filament (34%), and usually joined the trunk of the accessory nerve directly before the jugular foramen. The mean number of rootlets of the CR was 4.9 (range 2–9) above the cervicomedullary junction. The CR of the accessory nerve was composed of two to nine rootlets, which were formed by the union of two to four short filaments and joined the spinal root of the accessory nerve. The CR is morphologically distinct from the vagus nerve, confirming its existence. Clin. Anat. 27:1167–1173, 2014. © 2014 Wiley Periodicals, Inc.     

Is the cranial accessory nerve really a portion of the accessory nerve? Anatomy of the cranial nerves in the jugular foramen

The accessory nerve is traditionally described as having both spinal and cranial roots, with the spinal root originating from the upper cervical segments of the spinal cord and the cranial root originating from the dorsolateral surface of the medulla oblongata. The spinal rootlets and cranial rootlets converge either before entering the jugular foramen or within it. In a recent report, this conventional view has been challenged by finding no cranial contribution to the accessory nerve. The present study was undertaken to re-examine the accessory and vagus nerves within the cranium and jugular foramen, with particular emphasis on the components of the accessory nerve. These nerves were traced from their rootlets attaching to the spinal cord and the medulla and then through the jugular foramen. The jugular foramen was exposed by removing the dural covering and surrounding bone. A surgical dissecting microscope was used to trace the roots of the glossopharyngeal nerve (CN IX), vagus nerve (CN X) and accessory nerve (CN XI) before they entered the jugular foramen and during their travel through it. The present study demonstrates that the accessory nerve exists in two forms within the cranial cavity. In the majority of cases (11 of 12), CN XI originated from the spinal cord with no distinct contribution from the medulla. However, in one of 12 cases, a small but distinct connection was seen between the vagus and the spinal accessory nerves within the jugular foramen.     

舌咽神经、迷走神经和副神经断层解剖与MRI

目的：探讨舌咽神经、迷走神经和副神经的走行和毗邻关系,为影像学诊断及临床开展该区手术提供形态学依据。方法：利用36例成尸头部连续横断层标本和15例成尸头部连续冠状断层标本,并与10例志愿者的3D—CISS序列MR图像进行对照,观察舌咽神经、迷走神经和副神经在颅内的走行规律及其与周围结构的位置关系。结果：舌咽、迷走和副神经由上而下从延髓的橄榄后沟发出,跨过延池,穿颈静脉孔出颅。根据走行,可分其为延髓内段、脑池段和颈静脉孔段。在脑池段,舌咽神经走行在上方,迷走神经和副神经在下方且结合紧密;在颈静脉孔段,这3对脑神经及其与颈内静脉和颈内动脉的关系是：颈内动脉位于最前方,颈内静脉位于最外侧,舌咽神经走行在前内上方,有单独的硬脊膜包绕,迷走神经和副神经位于其后外下方,形成迷走、副神经复合体。结论：在标本的连续断面和对应的MR图像上能够清楚地显示舌咽、迷走和副神经的走行和毗邻关系。     

Neurons of origin of the internal ramus of the rabbit accessory nerve: localization in the dorsal nucleus of the vagus nerve and the nucleus retroambigualis

The neurons of origin of the internal ramus of the rabbit accessory nerve were identified in the dorsal nucleus of the vagus nerve, using bilateral injections of horseradish peroxidase into the inferior vagal ganglion, soft palate, and pharynx, which were preceded by different combinations of the unilateral intracranial severings of the rootlets of the vagus and glossopharyngeal nerves, those of the cranial root of the accessory nerve, and the trunk of its spinal root. The neurons of origin occupied the caudal four-fifths of the dorsal vagal nucleus extending from about 1.0 mm rostral to the obex as far caudally as the second cervical spinal segment, with their number being about half the total number of neurons of the nucleus. Although considerably fewer, they were also located in the nucleus retroambigualis of the caudal half of the first cervical spinal segment and the second segment. Axons of most internal ramus neurons traversed the rootlets of the cranial accessory root. Axons of the few neurons located more caudally than about 1.0 mm caudal to the obex emerged from the upper cervical spinal cord to run along the trunk of the spinal accessory root before finally joining the internal ramus; caudal to the midlevel of the first cervical segment, the dorsal vagal nucleus and the nucleus retroambigualis contained neurons whose axons followed only that course.     

颅后窝三角显微解剖及临床意义

目的：研究颅后窝三角的显微特征，为颅后窝手术提供快速辨认神经、血管的方法。方法：旁正中切口、乙状窦后入路，逐层开颅并切开硬脑膜，显微观察12具成人头部标本硬脑膜形成的三角。结果：颅后窝硬脑膜皱襞反光形成一个三角形：外上顶点即“光点”，位于横窦与乙状窦移行处的前方；内上顶点恰是岩静脉注入岩上窦的位置；颈静脉孔构成颅后窝三角内下顶点。结论：手术显微镜下，颅后窝硬脑膜形成的标志性三角，可以帮助迅速辨认三叉神经、岩静脉，经过内耳门的面神经、前庭蜗神经以及经过颈静脉孔的舌咽神经、迷走神经、副神经。     

Connection types between the spinal root of the accessory nerve and the posterior roots of the C2–C6 spinal nerves

Purpose  The aim of this study was to demonstrate the connection types and frequency between the accessory nerve and the posterior roots of the C2–C6 cervical nerves. Methods  The cranial cervical regions of 49 specimens from 27 human cadavers were used for the present study under an operating microscope. Results  Five different connection types between the accessory nerve and the posterior roots of the cervical nerves were recorded and photographed (types A–F). One of these types was not described previously in literature (type F). All connections between the posterior roots of the C2–C6 spinal nerves and the accessory nerve were at the level of the C2 segment. Type B was the most frequently seen type in our series. One of the rootlets of the cervical posterior root joined the accessory nerve without a connection to the spinal cord in type B. Conclusions  The clinical importance of these connections is especially noticed during the radical neck dissection as it may lead to the development of the shoulder-arm syndrome.     

Intradural anastomoses between the accessory nerve and the posterior roots of cervical nerves: their clinical significance.

This study was performed to identify the anastomoses between the accessory nerve and the posterior roots of cervical nerves below the level of C1 segment, and to evaluate their clinical significance. One hundred spinal cord sides of Koreans were studied under the surgical microscope. In order to trace the posterior root of a cervical nerve after anastomosis with the accessory nerve, or the bridging fibers between the accessory nerve and the cervical posterior roots, the accessory nerves with the posterior roots and the bridging fibers were stained with osmium tetroxide. The anastomosis was classified into five types, according to whether the accessory nerve and the cervical posterior root crossed each other, and also according to the site of the bridging fiber between them. The bridging fibers in the most common type of anastomoses were observed to connect the posterior roots of a cervical nerve with the spinal rootlet of the accessory nerve. The possibility that the motor fibers of accessory nerve from the spinal cord may innervate the trapezius muscle through the cervical nerve, was discussed.     

The relationship of the posterior inferior cerebellar artery to cranial nerves VII-XII

The posterior inferior cerebellar artery (PICA) is the largest branch of the vertebral artery. It usually arises at the anterolateral margin of the medulla oblongata close to the lower cranial nerves. The PICA had the most complex relationship to the cranial nerves of any artery and it is frequently exposed in approaches directed to the fourth ventricle. The aim of this article is to describe the anatomical relationship of the PICA to the lower cranial nerves. In this study, 12.5% of PICAs passed between the glossopharyngeal and vagus nerves, 20% between the vagus and accessory nerves, and 65% through the rootlets of the accessory nerve. The lateral medullary segment of the PICA showed a lateral loop which in 20% specimens pressed against the inferior surfaces of the facial and vestibulocochlear nerves. The lateral medullary segment of the PICA in 20% specimens passed superior to the hypoglossal nerve, in 47.5% through the rootlets of the hypoglossal nerve, and in 30% inferior to the hypoglossal nerve. The findings on the relationship of the PICA to the lower cranial nerves could be helpful in microsurgery of this region.     

Ascending vermian artery, branch of the V4 segment of the vertebral artery

A previously undescribed anatomical variant is reported here, that of vermian arteries (vAs) branched from the vertebral arteries (VAs) and replacing the medial branches of the posterior inferior cerebellar arteries (PICAs) that, in turn, were leaving the basilar artery. Both vAs left the VAs in the foramen magnum. The left vA initially looped in front of the spinal root of the accessory nerve (Sp11) and then looped inferiorly on the dorsal side of the spinal cord, in the vertebral canal and continued ascending on the dorsal surface of the medulla oblongata. The right vA looped dorsally to the Sp11 above the foramen magnum, and also ascended dorsally to the medulla. Both vAs were distributed to the vermis. On both sides, the PICAs looped above the glossopharyngeal nerves and the jugular foramina and continued as only lateral terminal branches of a normal PICA that descended in countercurrent on the outer side of the variant vAs. Such anatomical variation is relevant for surgery and microsurgery on both sides of the foramen magnum and in the posterior cerebral fossa.     

Vagal baro‐ and chemoreceptors in middle internal carotid artery and carotid body in rat

The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body. Although neurons in the nodose ganglion were labelled after injecting tracer into the carotid body, the vagal pathway to these baro‐ and chemoreceptors has not been identified. Neither has the glossopharyngeal intracranial afferent/sensory pathway that connects to the brainstem been defined. We investigated both of these issues in male Sprague–Dawley rats (n = 40) by injecting neural tracer wheat germ agglutinin‐horseradish peroxidase into: (i) the peripheral glossopharyngeal or vagal nerve trunk with or without the intracranial glossopharyngeal rootlet being rhizotomized; or (ii) the nucleus of the solitary tract right after dorsal and ventral intracranial glossopharyngeal rootlets were dissected. By examining whole‐mount tissues and brainstem sections, we verified that only the most rostral rootlet connects to the glossopharyngeal nerve and usually four caudal rootlets connect to the vagus nerve. Furthermore, vagal branches may: (i) join the CSN originating from the pharyngeal nerve base, caudal nodose ganglion, and rostral or caudal superior laryngeal nerve; or (ii) connect directly to nerve endings in the middle segment of the ICA or to chemoreceptors in the carotid body. The aortic depressor nerve always presents and bifurcates from either the rostral or the caudal part of the superior laryngeal nerve. The vagus nerve seemingly provides redundant carotid baro‐ and chemoreceptors to work with the glossopharyngeal nerve. These innervations confer more extensive roles on the vagus nerve in regulating body energy that is supplied by the cardiovascular, pulmonary and digestive systems.     

Morphological study on the rootlets comprising the root of the intermediate nerve

The number and arising sites of the rootlet comprising the intermediate nerve root were investigated in 100 sides of human brains. The arising sites of the rootlets were the pons halfway between the facial and vestibulocochlear nerves (31.9%), the arising portion of the vestibulocochlear nerve on the pons (28.8%) and the stem of the vestibulocochlear nerve (15.9%). The number of roots varied from one to five, with the most common being one root (58%). The number of rootlets per root also varied from one to five. Most of the roots had one rootlet (63%), while 2% of the roots had five rootlets. The variation of the arising sites of the intermediate nerve rootlets and its clinical significance were also discussed.     

腰骶部脊神经根的临床解剖学

通过临床选择性脊神经后根切断术中观察与测量,为临床提供了重要的参考数据。腰骶神经前、后根解剖会合点至椎间孔距离平均为1.5～2.0cm。前后两根相比,后根明显较前根粗,其中以L_5后根最粗、L_2～S_1各后根内小束的数目为4～18束,平均为7束,临床分离后根时可分为7束,以便进行电刺激选择。这些资料为腰骶部选择性脊神经后根切断术和马尾神经的手术提供了重要依据。     

颈静脉孔的放射解剖学

对200侧正常颈静脉孔的X线影像和20侧尸头颈静脉孔进行了观测。颈静脉孔有单、双孔之分,左侧的单、双孔分别占86%和14%,右侧的分别占80%和20%。单孔的形态可分四种,双孔的间隔为骨桥。左、右侧颈静脉孔的面积分别为46mm~2和62mm~2。颈内静脉位于孔的后外侧部,舌咽神经位于前内侧部,迷走神经和副神经可位于前内侧部、后外侧部或二部交界处。     

Projections from the reticular formation of the medulla, the spinal trigeminal and lateral reticular nuclei to the inferior olive

Injections of tritiated L-leucine were placed in the reticular formation of the medulla, the spinal trigeminal and lateral reticular nuclei of cats and silver grain accumulations in the inferior olivary nucleus were demonstrated by autoradiography. Cells of the reticular formation located at the junction of nuclei reticularis magnocellularis and reticularis parvocellularis in the rostral medulla and within nucleus reticularis ventralis in the caudal medulla contribute four distinct projections to the olive. Three projections are distributed ipsilaterally in the caudal part of the medial accessory olive, at mid-level of the dorsal accessory olive and in the ventrolateral bend of the principal olive, at rostral levels. There is also a small controlateral projection to the caudal part of the medial accessory olive. the spinal trigeminal nucleus sends crossed projections to the rostral part of the dorsal accessory olive and adjacent ventral lamella as well as to the caudal part of the medial accessory olive. The lateral reticular nucleus sends an extensive ipsilateral projection to the caudal part of the medial accessory olive and provides a small contribution to the same subdivision, contralaterally. All these projections converge with other known afferents to the olive.     

Distribution of Neuron Cell Bodies in the Intraspinal Portion of the Spinal Accessory Nerve in Humans

The spinal accessory nerve is often identified as a purely motor nerve innervating the trapezius and sternocleidomastoid muscles. Although it may contain proprioceptive neurons found in cervical spinal levels C2–C4, limited research has focused on the histology of the spinal accessory nerve. The objective of the present study was to examine the spinal accessory nerve to determine if there are neuronal cell bodies within the spinal accessory nerve in humans. Cervical spinal cords were dissected from eight cadavers that had previously been used for dissection in other body regions. The segmental rootlets were removed to quantify the neuron cell bodies present at each spinal level. Samples were embedded in paraffin; sectioned; stained with hematoxylin and eosin; and examined using a microscope at 4×, 10×, and 40× magnification. Digital photography was used to image the samples. Neuronal cell bodies were found in 100% of the specimens examined, with non‐grossly visible ganglia found at spinal levels C1–C4. The C1 spinal level of the spinal accessory nerve had the highest number of neuron cell bodies. Anat Rec, 299:98–102, 2016. © 2015 Wiley Periodicals, Inc.     

侧颅底的矢状和冠状断层解剖及临床意义

目的为侧颅底病变的影像诊断及手术入路提供解剖学基础。方法选取成人尸体头颈部40例,分别作矢、冠状断层解剖。在经颈动脉管垂直段、卵圆孔矢状层面上和经卵圆孔、茎突根部冠状层面上,观察侧颅底结构的解剖学关系,利用游标卡尺测量侧颅底内重要结构的径线及结构之间的距离。结果侧颅底的矢、冠状断层可清晰显示卵圆孔、颈静脉孔、颈动脉管垂直段、颈静脉窝、颞下颌关节、茎突等侧颅底结构及其毗邻关系和咽旁间隙内的结构,颈动脉管外口、卵圆孔和茎突根部至颈静脉孔的距离分别为(16.60±2.34)、(22.70±1.64)、(21.14±2.05)mm。茎突是侧颅底影像诊断及手术入路时观察各结构间的位置关系和寻找神经、血管的骨性标志。两侧侧颅底结构呈对称性分布,重要结构的径线及结构之间的距离均无显著性差异。结论侧颅底的矢、冠状断层是分别显示内耳道内结构和颞下间隙的最佳断层影像方式,对侧颅底病变的影像诊断和设计手术入路等具有重要意义。     

鸡舌咽神经传入纤维在中枢的分布

目的 研究鸡舌咽神经传入纤维在中枢的分布。方法 选用10只健康来抗鸡,分离暴露舌咽神经干,在岩神经节处注射4μlCB－HRP,动物存活35小时,灌注固定,取延髓作冰冻连续切片,FMB法呈色,光镜下观察。结果 鸡舌咽神经传入纤维主要投射到注射侧孤束核闩前部的前中部,部分投身到三叉神经脊束与三叉神经脊束核、楔外侧核及第1、2颈髓脊侧角的背外侧。结论 鸡孤束核闩后部及闩前部的后部仅接受迷走传入投射,闩前部的前部同时接受迷走神经和舌咽神经的传入投射。     

Morphologic study of the connections between the accessory nerve and the posterior root of the first cervical nerve

The purpose of this study was to evaluate the anastomotic relationships between the accessory nerve and the posterior root of the first cervical nerve and to determine the course of the posterior root nerve fibers after anastomosis. The relationships between these two nerves were studied in 100 sides of the spinal cord and then classified into four types. In the most common type of anastomosis (38% of cases), either a branch from the posterior C1 root was seen to course cranially and join the accessory nerve, or the posterior root and accessory nerve fused as they coursed orthogonal to one other. In the second most common type (36% of cases), the accessory nerve anastomosed with a posterior C1 root that had no direct connection with the spinal cord; the nerve fibers of the posterior root were observed in stained samples to course caudally along the accessory nerve and join the posterior C2 root. In the least common type (6% of cases), no connection was observed between the accessory nerve and the posterior C1 root. In the next least common type (20% of cases), the posterior C1 root was absent and a connecting branch was sometimes observed between the accessory nerve and the anterior C1 root.