Anatomy of the spinal accessory nerve plexus: relevance to head and neck cancer and atherosclerosis

The term spinal accessory nerve plexus may be defined as the spinal accessory nerve with all its intra- and extracranial connections to other nerves, principally cranial, cervical, and sympathetic. The term is not new. This review examines its applied anatomy in head and neck cancer and atherosclerosis. Over the centuries, general studies of neural and vascular anatomy and embryology formed a basis for the understanding upon which the plexus is described. During the past century, its anatomy and blood supply have come to be better understood. The importance of almost all of the plexus to head, neck, and upper extremity motor and sensory functions has come to be realized. Because of this understanding, surgical neck dissection has become progressively more conservative. This historical progression is traced. Even the most recent anatomic studies of the spinal accessory nerve plexus reveal configurations, new to many of us. They were probably known to classical anatomists, and not recorded in readily available literature, or not recorded at all. Human and comparative anatomic studies indicate that the composition of this plexus and its blood supply vary widely, even though within the same species their overall function is very nearly the same. Loss of any of these structures, then, may have very different consequences in different individuals. As a corollary to this statement, data are presented that the spinal accessory nerve itself need not be cut during surgical neck dissections for severe impairment to occur. In addition, data are presented supporting the theory that atherosclerosis by obstructing vessels to this plexus and its closely connected brachial plexus will very likely result in their ischemic dysfunction, often painful. Finally evidence, as well as theory, is stated concerning anatomic issues, methodology, outcome, and possible improvements in surgical procedures emphasizing conservatism.     

Depletions in the cervical and thoracolumbar sympathetic system following removal of neural crest from the embryo of Chelydra serpentina

Neural crest and dorsal neural tube of cervical and thoracolumbar levels were removed from embryos of Chelydra serpentina at stages ranging from 8 to 18 somites. Extirpation extended from the levels of the last four somites posteriorly around the neurenteric canal. Deficiencies in sensory and sympathetic ganglia occurred. Motor roots of the associated spinal nerves differentiated. In the absence of postganglionic neurons, the preganglionic fibers form a neuron-free plexus in the thoracolumbar region. Some observations in the cervical region indicate that the postganglionic neurons depend on preganglionic fibers for their differentiation. The cortex of the adrenal gland formed without related medulla in appropriate experiments. The normal morphology of the sympathetic trunks is illustrated. Superficial and deep cervical sympathetic trunks are described. The latter ascends the neck in a paravertebral position. Along its course are segmental ganglia and rami communicantes; it terminates by joining the medial branch of the superficial sympathetic trunk rostral to the ninth cranial nerve.     

The harvest and clinical application of the superficial peroneal sensory nerve for grafting motor and sensory nerve defects.

Potential donor nerves for autografting are finite and usually limited to cutaneous nerves of the extremities. The superficial peroneal nerve is the major lateral branch of the common peroneal nerve that innervates the peroneus longus and brevis muscles and provides sensation to the lateral aspect of the lower leg and the dorsal foot. It has generally been overlooked as a potential donor of nerve autografts. Cadaver dissections were performed on 10 fresh lower extremity specimens to investigate the anatomic characteristics of the superficial peroneal nerve and to refine a harvesting technique for the nerve. Thirty-one patients underwent nerve grafting of 39 upper and lower extremity nerves using the superficial peroneal donor. There were nine median nerves, four ulnar nerves, two radial nerves, two brachial plexus lesions, 16 digital nerves, and six lower extremity nerves grafted. The superficial peroneal nerve provided a consistently long donor, comparable in length to the sural nerve. The anatomic pattern is consistent, the patient positioning is simple, the surgical harvesting technique is straightforward, and the donor defect is acceptable. The superficial peroneal nerve provides a safe and valuable donor nerve, particularly in cases where multiple or very long nerve grafts are required.     

Innervation of the dermatomes in the neck of the mouse

The dorsal rami of the cervical and thoracic spinal nerves were investigated using both the in situ cholinesterase staining technique and cholinesterase staining on serial sections of plastic-embedded embryos. In most cases only the dorsal rami of the 2nd to 5th cervical spinal nerve possess cutaneous branches. The area innervated by the cutaneous branch of the dorsal ramus of the 5th spinal nerve borders on an area innervated by the cutaneous branch of the dorsal ramus of the 1st thoracic spinal nerve. The dorsal rami of the cervical spinal nerves 6-8 show no cutaneous branches. Therefore the gap in the series of the dorsal cutaneous branches is due only to the middle part of the nerves of the brachial plexus, which range from the 5th cervical nerve to the 1st thoracic nerve.     

HEADACHE OF EXTRACRANIAL ORIGIN

The cervical spine, usually regarded as a supporting structure for the head, is also an important viaduct of vessels and nerves which must function with little clearance in a congested and moving space bounded by bone. Pressure in this viaduct is an important cause of headache.The cervical foramina although apparently roomy, are constricted by cartilage, by the vertebral artery and its adnexae, and by the lateral intervertebral joints. Osteophytosis, swelling or adhesion in this constricted space almost inevitably causes painful vascular or neural disorder.In certain postures of the neck the vertebral artery is constricted or even occluded. Traction or sprain may likewise cause headache through disturbance of the vertebral arterial nerves, the posterior cervical autonomic system or the spinal accessory nerves which originate in delicate filaments from all points of the cervical spinal cord.A syndrome described by Skillern—migraine-like suboccipital and retro-orbital headache—is due to disturbance of the second cervical nerve, which communicates with the first division of the trigeminal nerve.Headache due apparently to a minor scalp contusion may really be due to irritation of a trigger area at the site of an old scalp injury.     

Nerves and nerve plexuses of the human vertebral column

The origin, distribution, and termination pattern of nerves supplying the vertebral column and its associated structures have been studied in the human fetus by means of an acetylcholinesterase whole-mount method. The vertebral column is surrounded by ventral and dorsal nerve plexuses which are interconnected. The ventral nerve plexus consists of the nerve plexus associated with the anterior longitudinal ligament. This longitudinally oriented nerve plexus has a bilateral supply from many small branches of the sympathetic trunk, rami communicantes, and perivascular nerve plexuses of segmental arteries. In the thoracic region, the ventral nerve plexus also is connected to the nerve plexuses of costovertebral joints. The dorsal nerve plexus is made up of the nerve plexus associated with the posterior longitudinal ligament. This nerve plexus is more irregular and receives contributions only from the sinu-vertebral nerves. The sinu-vertebral nerves originate from the rami communicantes and, in the cervical region, also from the nerve plexus of the vertebral artery. Thick and thin sinu-vertebral nerves are found. Most frequently three types of thick sinu-vertebral nerves are observed, i.e., ascending, descending, or dichotomizing ones. Finally, the distribution of the branches of the ventral and dorsal nerve plexuses and of the sinu-vertebral nerves is described.     

Isolation and characterization of axolemma-enriched fractions from rabbit and bovine peripheral nerve

Axolemma-enriched fractions were isolated from bovine spinal accessory nerves, bovine intradural dorsal roots, and rabbit sciatic nerve by differential centrifugation and separation on a linear 10–40% sucrose (w/w) gradient. The fractions were enriched 4 to 10 fold in acetylcholinesterase, a biochemical marker for axolemma. Axolemma-enriched fractions isolated from uniformly well-myelinated fibers (bovine spinal accessory nerve) contained lower CNPase activity and higher acetylcholinesterase activity than comparable fractions isolated from variably myelinated fibers (rabbit sciatic nerve and bovine intradural roots). Separation by polyacrylamide electrophoresis showed that the molecular weight distribution of all peripheral nerve axolemma-enriched fractions was similar and ranged from 20 to over 150 kilodaltons. All axolemma-enriched fractions appeared to contain a small but variable amount of myelin-specific proteins. Based on biochemical properties, peripheral nerves containing uniformly well-myelinated fibers yield an axolemma-enriched fraction which is least contaminated with myelin-related membranes.     

Die Halsäste des Nervus vagus beim Alpaka,Lama guanicoe pacos (Linné 1758)

Demmel, U. 1980. Die Halsäste des Nervus vagus beim Alpaka, Lama guanicoe pacos (Linné 1758). [The branches of the vagus nerve in the neck of Alpaka, Lama guanicoe pacos (Linné 1758).] (Anatomisches Institut der Universität Köln, Bundesrepublik Deutschland.) — Acta zool. (Stockh.) 61(3): 141–146. Dissections of two newborn and two adult alpacas have shown: that the trapezius musculature of either side is supplied by branches of seven cervical spinal nerves and not by the external ramus of truncus nervi accessorii as in mammals in general; that the nerves which innervate the inner laryngic muscles as well as the mucous membrane of the lower part of the larynx are given off from the main trunk of the vagus nerve just outside the jugular foramen; that a nerve corresponding to the n. laryngeus recurrens of other mammals is absent. It is concluded that the lack of recurvation of the inferior laryngic nerve and the absence of the spinal part of the accessory nerve are character states of tylopod artiodactyls.     

An immunohistochemical study on the innervation of SP-IR nerves in the cerebral arteries of the bent-winged bat

Summary The overall distribution of substance P (SP) immunoreactive (IR) nerves surrounding the cerebral arteries of the bent-winged bat were investigated immunohistochemically. In this microchiropteran species, the walls from the vertebral artery to the caudal part of the basilar artery have considerably well-developed plexuses of SP-IR nerves, whereas no demonstrable SP-IR fibers were found in the crostral part of the basilar artery, and in more rostrally located arteries the nerve supply was very sparse or occasionally lacking. This innervation pattern has not yet been established for the cerebral arterial systems of other mammals that have been studied under normal conditions, but it is very similar to the pattern of SP-IR innervation observed in the guinea pig and cat of which the trigeminal ganglia have been destroyed. From the combination of this and other immunohistochemical findings, it is suggested that SP-IR nerves innervating the vertebral and basilar arteries of the bent-winged bat originate from the upper cervical dorsal root ganglia (DRG) and enter the cranial cavity along the vertebral artery and through the meninges.Abbreviations BA basilar artery - CSN cervical spinal nerves - ICS internal carotid system - SCG superior cervical ganglion - SNB sympathetic nerve bundle - VA vertebral artery - VBS vertebro-basilar system     

The effect of diet upon the fatty acid composition of cranial and spinal nerve lipids.

The possible basal differences in lipid class and fatty acid composition between a cranial nerve (the trigeminal nerve) and two spinal nerves (the ulnar and sciatic nerves) as well as the effects of dietary lipids on the same nerves were studied. A basal (BD) and four experimental diets containing respectively hydrogenated coconut oil (HCO), grapestone oil (GSO), olive oil (OO) and linseed oil (LSO) were used. Trigeminal lipids fatty acid composition differs significantly from sciatic and ulnar ones in the percentages of 16:0, 16:1, 18:0, 18:2 n-6, 20:0, 20:1, 20:4 n-6, 24:0, 24:1 and 22:6 n-3. Also the proportions of triacylglycerols and free cholesterol strongly differ in trigeminal and spinal nerves whereas no significant difference was detected between ulnar and sciatic nerve lipids. Following the administration of the four experimental diets for 60 days, no significant change was observed in the fatty acid pattern of trigeminal lipids while the spinal ones showed a significant increase in the proportions of the fatty acids present in large quantities in the dietary oils used (i.e.: oleic acid in the OO samples). These changes are probably linked with the rapid metabolic turnover of triacylglycerols, present in larger amounts in spinal nerve lipids.     

Fluorescence histochemical study on regional differences in the sympathetic nerve supply of the choroid plexus from various laboratory animals

Summary The adrenergic nerve supply of the choroid plexus in all four ventricles was studied by the Falck-Hillarp histofluorescence technique in nine different species, and the noradrenaline concentration in whole plexus tissue was determined by a radioenzymatic method. The nerve density was usually in the order: third > lateral > fourth ventricular plexuses. Plexuses of the pig and cat possessed the largest number of nerves; the innervation was intermediary in the baboon, guinea-pig, rat, rabbit and hamster, whereas only few fluorescent nerves were found in the cow and mouse plexuses. Sympathetic denervation showed an ipsilateral supply from the superior cervical ganglia to the lateral plexuses and a mixed contribution to the midline plexuses. The total noradrenaline concentration varied between 0.10 and 0.73 ng per mg protein.     

Projection of the celiac plexus to the afferent centers demonstrated by the horseradish peroxidase retrograde transport method

Using the horseradish peroxidase (HP) retrograde method for ascertaining connections of the celiac plexus of the white rat with various afferent centers, HP-marked neurocytes have been revealed in caudal nodes of the vagus nerves and in spinal nodes at the Th4-L2 level. Negative results have been obtained at investigation of the cervical spinal nodes and intramural nodes in the cat ileocecal part. Similar data are obtained, when connections of the celiac plexus with the same area of the cat gut are investigated. Therefore, the problem on interrelations of the celiac plexus with the proper afferent centers of the diaphragmatic+ nerve and the second type cells of Dogel in the cat intramural ganglia is still disputable.     

The equine neck and its function during movement and locomotion

During both locomotion and body movements at stance, the head and neck of the horse are a major craniocaudal and lateral balancing mechanism employing input from the visual, vestibular and proprioceptive systems. The function of the equine neck has recently become the focus of several research groups; this is probably also feeding on an increase of interest in the equine neck in equestrian sports, with a controversial discussion of specific neck positions such as maximum head and neck flexion. The aim of this review is to offer an overview of new findings on the structures and functions of the equine neck, illustrating their interplay. The movement of the neck is based on intervertebral motion, but it is also an integral part of locomotion; this is illustrated by the different neck conformations in the breeds of horses used for various types of work. The considerable effect of the neck movement and posture onto the whole trunk and even the limbs is transmitted via bony, ligamentous and muscular structures. Also, the fact that the neck position can easily be influenced by the rider and/or by the employment of training aids makes it an important avenue for training of new movements of the neck as well as the whole horse. Additionally, the neck position also affects the cervical spinal cord as well as the roots of the spinal nerves; besides the commonly encountered long-term neurological effects of cervical vertebral disorders, short-term changes of neural and muscular function have also been identified in the maximum flexion of the cranial neck and head position. During locomotion, the neck stores elastic energy within the passive tissues such as ligaments, joint capsules and fasciae. For adequate stabilisation, additional muscle activity is necessary; this is learned and requires constant muscle training as it is essential to prevent excessive wear and tear on the vertebral joints and also repetitive or single trauma to the spinal nerves and the spinal cord. The capability for this stabilisation decreases with age in the majority of horses due to changes in muscle tissue, muscle coordination and consequently muscle strength.     

Submandibular gland I: an anatomic evaluation and surgical approach to submandibular gland resection for facial rejuvenation

Submandibular gland resection for aesthetic reasons has been hotly debated. Detractors maintain that the procedure is dangerous because it puts too many important structures at risk, notably motor nerves. The present study was undertaken to elucidate the neurovascular and soft-tissue anatomy of the digastric triangle via cadaver dissections so that a surgical approach to achieve safe aesthetic submandibular resection could be performed. Fifteen digastric triangles dissections were performed in fixed and fresh cadaver specimens. The dissection focus was to understand the submandibular neurovascular relationships, capsule as well as fascial layers, and measurements to known structures. The marginal mandibular nerve is located external to the submandibular capsule, approximately 3.7 cm cephalad to the inferior margin of the gland. The hypoglossal nerve is posterior to the digastric sling in a position that is protected deep within the visceral layer of the neck. The lingual nerve is located underneath the mandibular border, crossing anterior to the submandibular duct. The vascular supply is variant, but with an average of one and a half vessels entering medially to the superficial lobe of the gland, one intermediate vessel entering medially to supply the superficial and deep lobes, and one deep perforator that runs from the central portion of the deep lobe to the superficial lobe. Appreciation of this anatomy is critical in the submental approach for partial resection. Although it can be technically challenging, the anatomy is straightforward and partial submandibular gland resection can be executed via a consistent, safe approach to optimize facial rejuvenation in certain patients.     

Long head of the triceps branch transfer to axillary nerve in C5, C6 brachial plexus injuries: anterior approach

Shoulder abduction is a very complex movement and quite important for upper limb function, as more distal functions depend on a stable shoulder, especially in C5, C6 brachial plexus injuries. Various studies in the literature have emphasized the importance of improved functional outcome and shoulder reanimation with concomitant neurotization of suprascapular nerve and axillary nerve in C5, C6 brachial plexus injuries. A number of approaches to axillary nerve transfer in brachial plexus injuries have been reported. The author describes an innovative anterior deltopectoral approach for axillary nerve transfers in five patients with C5, C6 brachial plexus injuries. The spinal accessory nerve was neurotized with the suprascapular nerve through a transverse supraclavicular incision. The axillary nerve and the long head of the triceps branch were identified through the anterior deltopectoral approach and neurotized at the posterior cord level. This approach gives easy access to other donors such as the medial pectoral, thoracodorsal, and median and ulnar nerves. Oberlin's transfer was also performed for elbow flexion by extending the deltopectoral incision. The regained shoulder active abduction (M5) averaged 120 degrees and active external rotation averaged 65 degrees at the final follow-up of 26 months (average). This anterior deltopectoral approach is an excellent alternative for axillary nerve transfer in brachial plexus injuries and produces results comparable with those of other approaches. All brachial plexus surgeons must understand the anatomy and the relationship of the axillary nerve to the surrounding structures. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.     

Altered alignment of the shoulder girdle and cervical spine in patients with insidious onset neck pain and whiplash-associated disorder

Clinical theory suggests that altered alignment of the shoulder girdle has the potential to create or sustain symptomatic mechanical dysfunction in the cervical and thoracic spine. The alignment of the shoulder girdle is described by two clavicle rotations, i.e, elevation and retraction, and by three scapular rotations, i.e., upward rotation, internal rotation, and anterior tilt. Elevation and retraction have until now been assessed only in patients with neck pain. The aim of the study was to determine whether there is a pattern of altered alignment of the shoulder girdle and the cervical and thoracic spine in patients with neck pain. A three-dimensional device measured clavicle and scapular orientation, and cervical and thoracic alignment in patients with insidious onset neck pain (IONP) and whiplash-associated disorder (WAD). An asymptomatic control group was selected for baseline measurements. The symptomatic groups revealed a significantly reduced clavicle retraction and scapular upward rotation as well as decreased cranial angle. A difference was found between the symptomatic groups on the left side, whereas the WAD group revealed an increased scapular anterior tilt and the IONP group a decreased clavicle elevation. These changes may be an important mechanism for maintenance and recurrence or exacerbation of symptoms in patients with neck pain.     

Confocal imaging and phylogenetic considerations of the subcutaneous neurons in the Atlantic hagfish Myxine glutinosa

We used confocal microscopy and immunohistochemistry to characterize the morphology of the subcutaneous neurons and the innervation of the slime glands and striated muscles in the hagfish Myxine glutinosa. A rich plexus of 5HT‐, ChAT‐ and TH‐positive neurons is described in the capsule of the slime glands. These neurons, like those of the subcutaneous plexus, receive pericellular terminations from the axons of central cells. Capsular neurons receive innervation from 5HT‐positive and nNOS‐positive nerve fibres. Other nerve endings belonging to two separate nerve populations are identified in the striated muscles. They contain TH and nNOS immunoreactivity. Due to the lack of any topographical labelling, the cell origin and the projections of the neurons into the cranial and spinal nerves are unknown. This study provides anatomical evidence of multiple (5HT and nNOS) peripheral innervation of the neurons. However, it does not provide information about the function of these neurons in the hagfish. We suggest that hagfish neurons have a phylogenetic relationship with the spinal group of the dorsal cells of lampreys and the supramedullary cells of teleosts.     

Distribution and origins of VIP-immunoreactive nerves in the cephalic circulation of the cat

VIP-immunoreactive (IR) nerves were visualized in whole mounts and sections of cephalic arteries and cranial nerves of cats with indirect immunofluorescence. Perivascular VIP-IR nerves were very widely distributed in arteries and arterioles supplying glands, muscles and mucous membranes of the face. Within the cerebral circulation, perivascular VIP-IR nerves were most abundant in the Circle of Willis and the proximal portions of the major cerebral arteries and their proximal branches supplying the rostral brain stem and ventral areas of the cerebral cortex. VIP-IR nerves were absent from arterial branches supplying the posterior brain stem, cerebellum and dorsal cerebral cortex. Cerebral perivascular VIP-IR nerves probably arise from VIP-IR perikarya within microganglia found in the cavernous plexus and external rete. Extracerebral perivascular VIP-IR nerves probably arise from VIP-IR perikarya in microganglia associated with the tympanic plexus, chorda tympani, lingual nerve and Vidian nerve as well as from cells in the otic, sphenopalatine, submandibular and sublingual ganglia. It seems likely, therefore, that each major segment of the cephalic circulation is supplied by local VIP-IR neurons.