Surgical anatomy of spinal accessory nerve: is trapezius functional deficit inevitable after division of the nerve?

The course of spinal accessory nerve in the posterior triangle, the innervation of the sternocleidomastoid and trapezius muscles and the contributions from the cervical plexus were studied in 20 cadaveric dissections. The nerve was most vulnerable to iatrogenic injuries after leaving the sternocleidomastoid. Direct innervation of trapezius by cervical plexus branches was noted in five dissections, whereas connections between the cervical plexus and the spinal accessory nerve were observed in 19 dissections. These were usually under the sternocleidomastoid (proximal to the level of division of the nerve in nerve transfer procedures). Although the contribution from the cervical plexus to trapezius innervation is considered minimal, trapezius function can be protected in neurotization procedures by transecting the spinal accessory nerve distal to its branches to the upper position of trapezius.     

Innervation of the trapezius muscle: a study in patients undergoing neck dissections

Twenty-four patients with surgical section of the accessory nerve and/or its cervical contribution(s) were examined from 1 to 156 months after surgery, and compared to twenty controls. Thirteen patients had a classical neck dissection; seven had the whole length of the accessory nerve preserved but not the cervical plexus contributions. Four had the upper half of the accessory nerve sectioned, but with preservation of both the lower half and its cervical contributions. Clinical and electrophysiological studies of the three portions of the trapezius suggested the existence of an undescribed motor nerve supply to the trapezius and of a motor input from the cervical plexus contributions via the accessory nerve. The former is also supported by an anatomical study.     

A cadaveric study of the motor nerves to the levator scapulae muscle

Understanding the surgical anatomic relationships of the motor nerves to the levator scapulae muscle is imperative for reducing postoperative shoulder dysfunction in patients undergoing neck dissection. To elucidate this relevant anatomy, cervical (C3, C4) and brachial (C5 via dorsal scapular nerve) plexi contributions to the levator scapulae were assessed with respect to posterior triangle landmarks in 37 human cadaveric necks. An average of approximately 2 (actual 1.92) nerves from the cervical plexus (range 1 to 4 nerves) emerged from beneath the posterior border of the sternocleidomastoid muscle in a cephalad to caudad progression to enter the posterior triangle of the neck on their way to innervating the levator scapulae. These cervical plexus contributions exhibited a fairly regular relationship to the emergence of cranial nerve XI and the punctum nervosum along the posterior border of the sternocleidomastoid muscle. After emerging from the posterior border of the sternocleidomastoid to enter the posterior triangle of the neck, cervical plexus contributions to the levator scapulae traveled for a variable distance posteriorly and inferiorly, sometimes branching or coming together. Ultimately these nerves crossed the anterior border of the levator scapulae as 1 to 3 nerves (average 1.94) in a regular superior to inferior progression. The dorsal scapular nerve from the brachial plexus exhibited highly variable anatomic relations in the inferior aspect of the posterior triangle, and was found to penetrate or give branches to the levator scapulae in only 11 of 35 neck specimens. We have found that the levator scapulae receives predictable motor supply from the cervical plexus. Our data elucidate surgical anatomy useful to head and neck surgeons. (Otolaryngol Head and Neck Surg 1997;117:671-80.)     

Vulnerability of the spinal accessory nerve in the posterior triangle of the neck: a cadaveric study.

Injury to the accessory nerve results in an obvious shoulder droop, loss of shoulder elevation, and pain. Prevention of inadvertent injury to the accessory nerve is critical in neck dissection. No previous study, however, anatomically demonstrates the mechanism of the spinal accessory nerve traction injury. Anatomic determination of the location and course of the spinal accessory nerve may be helpful for a better understanding of the mechanism of the nerve injury. The accessory nerve courses obliquely across the posterior triangle on the surface of the levator scapula muscle and reaches the trapezius. The length of the spinal accessory nerve in the posterior triangle is 34.7+/- 6.3 mm. The nerve passes through the posterior border of the sternocleidomastoid muscle 50.7+/- 12.9 mm below the tip of the mastoid process and reaches the anterior border of the trapezius 49.8 +/- 5.9 mm above the clavicle. It makes a posterior angle of 73.1 degrees +/- 19.4 degrees, on average, relative to the posterior border of the sternocleidomastoid. When the shoulder is pulled down and the head is turned to the opposite direction, the spinal accessory nerve is stretched in the posterior triangle. In the posterior triangle, the nerve is vulnerable, since it is superficial and covered only by skin and subcutaneous fascia. Therefore, extreme caution should be taken with any surgical procedures in the posterior triangle. Traction injury of the spinal accessory nerve in the posterior triangle cannot be ignored.     

后入路副神经移位至肩胛上神经的应用解剖

目的 对斜方肌内的神经支配进行解剖学观察,为寻找副神经移位到肩胛上神经的最佳移位点和移位方式提供解剖依据.方法 选用成人尸体标本10具20侧.观察副神经在斜方肌内的行径及分支.并取不同水平副神经、肩胛上神经横断面制病理切片,计数各神经断面的神经纤维数,进行比较.结果 副神经在锁骨上2～3 cm进入斜方肌内,在肩胛冈中点前上方3～4 cm处,有来自颈丛的交通支加入后形成终末支.副神经的神经纤维计数:入斜方肌处(A点)为(1245±46)条,颈丛的交通支汇入前(B点)为(830±36)条,汇入后(C点)为(1074±38)条.结论 (1)副神经在与颈丛交通支合干后H-G段内的各断点,是副神经的最佳移位点.(2)后进路副神经移位术不影响斜方肌上部神经支配,充分利用了颈丛交通支,且缩短了神经再生距离,值得推广.     

Surgical management of trapezius palsy

BACKGROUND: Injury to the spinal accessory nerve in the posterior cervical triangle leads to paralysis of the trapezius muscle. The aim of this study was to determine the indications for nerve repair or reconstructive surgery according to the etiology, the duration of the preoperative delay, and specific patient characteristics. METHODS: Of twenty-seven patients with a trapezius palsy, twenty were treated with neurolysis or surgical repair (direct or with a graft) of the spinal accessory nerve and seven were treated with the Eden-Lange muscle transfer procedure. Lymph node biopsy was the main cause of the nerve injury. The nerve repairs were performed at an average of seven months after the injury, and the reconstructive procedures were done at an average of twenty-eight months. Nerve repair was performed for iatrogenic injuries of the spinal accessory nerve, within twenty months after the onset of symptoms, and in one patient with spontaneous palsy. Reconstructive surgery was performed for cases of trapezius palsy secondary to radical neck dissection, for spontaneous palsies, and after failure of nerve repair or neurolysis. The mean follow-up period was thirty-five months. The functional outcome was assessed clinically on the basis of active shoulder abduction, pain, strength of the trapezius on manual muscle-testing, and level of subjective patient satisfaction. RESULTS: The results were good or excellent in sixteen of the twenty patients treated with nerve repair and in four of the seven patients treated with the Eden-Lange procedure. Poor results were seen in older patients and in patients with a previous radical neck dissection. CONCLUSIONS: Good results can be expected from a repair of the spinal accessory nerve if it is performed within twenty months after the injury, as the nerve is basically a purely motor nerve and the distance from the injury to the motor end plates is short. Muscle transfer should be performed in patients with spontaneous trapezius palsy, when previous nerve surgery has failed, or when the time from the injury to treatment is over twenty months. Treatment is less likely to succeed when the patient is older than fifty years of age or the palsy was due to a radical neck dissection, penetrating injury, or spontaneous palsy.     

Innervation of the trapezius muscle by the intra-operative measurement of motor action potentials

Although the surgical anatomy of the spinal accessory nerve and the cervical plexus has been extensively described, the exact motor innervation of the trapezius has been controversial. Attempts to resolve this question have involved anatomic or electrophysiologic studies in human embryos and animals. Extrapolation of the results to adult humans may not be correct. Accurate identification of muscle innervation is obtainable by intra-operative measurement of motor action potentials produced by direct stimulation of the accessory nerve and the cervical plexus. The study involved 14 patients undergoing supraomohyoid or modified neck dissections. Under direct vision, stimulating electrodes were placed on the identified nerves and motor action potentials, and latencies were recorded by surface electrodes placed over the three portions of the trapezius. In 13 patients, when the accessory nerve was stimulated, motor action potentials were obtained in 13 of 13 in the first portion, 11 of 13 in the second portion, and 10 of 13 in the third portion of the trapezius. In the last patient, the accessory nerve ended in the sternocleidomastoid muscle, and innervation of the trapezius was via C3 as demonstrated by motor action potentials. Responses when the roots of the cervical plexus were stimulated varied. Three patterns were seen: In the first group (seven patients), motor action potentials were distinct from those recorded when the accessory nerve was stimulated. Additionally, latencies were different from those of the accessory nerve. The second group (four patients) had motor action potentials that were similar to those obtained from stimulation of the accessory nerve, although their corresponding latencies were different. In two patients, no motor action potentials were recorded when the cervical plexus was stimulated. The results suggest that motor innervation of the trapezius is variable. The accessory nerve, when present, provides the most important input to the trapezius. Motor innervation from the cervical plexus is unpredictable, although it appears to be present in the majority of patient studies.     

Surgical anatomy of the spinal accessory nerve in the posterior triangle of the neck

OBJECTIVE: The major complication of neck dissection and surgery at the posterior triangle of the neck is severe disability of the shoulder or "shoulder syndrome", which results from spinal accessory nerve injury. Surgical landmarks of the nerve in this area were studied. METHODS: Fifty-six fresh Thai cadavers (112 necks) were dissected to identify the anatomical relationship of the spinal accessory nerve and its commonly used landmarks. RESULTS: The spinal accessory nerve was found within 3.6 cm (mean, 1.43 cm) above Erb's point. The distance between the spinal accessory nerve entering the trapezius muscle and the clavicle was between 2.6 cm and 6.9 cm (mean, 4.5 cm). CONCLUSION: Our data were different from those described in the literature. Reconsideration of these two important landmarks can help to minimize iatrogenic injury of the spinal accessory nerve.     

Considering the spinal accessory nerve in head and neck surgery

Loss of trapezius muscle function represents the single most important source of long-term morbidity from a radical neck dissection. Its preservation has been one of the central features of the conservative or modified neck dissection. We recently undertook an evaluation of 100 consecutive patients who had undergone composite resection for head and neck cancer and examined them with particular emphasis on the function of the trapezius muscle. The mean interval from the time of radical neck dissection to the time of this evaluation was 6.2 years. The operations included radical neck dissection with sacrifice of the spinal accessory nerve, radical neck dissection with preservation of the spinal accessory nerve, and radical neck dissection with interpositioned cable graft reconstruction. The survey showed that 67 percent of the patients who underwent radical neck dissection with sacrifice of the spinal accessory nerve, although they showed profound atrophy of the trapezius muscle, had few symptoms related to this deficit. Similarly, 47 percent of patients who underwent radical neck dissection with preservation of the spinal accessory nerve showed some signs of muscle atrophy, and 20 percent showed little or no function of the muscle. Interpositioned nerve grafts appeared to function well in 66 percent of the patients. The survey showed that a surprising number of patients treated with a standard radical neck dissection and sacrifice of the spinal accessory nerve had few postoperative symptoms related to the loss of trapezius muscle function. Also unexpected was the number of patients with signs of muscle dysfunction despite nerve preservation.     

The anatomy of the accessory nerve and cervical lymph node biopsy

Injury to the accessory nerve is the most frequent complication of surgical procedures in the posterior triangle of the neck. The symptoms produced by paralysis of the trapezius are disabling. The components of this disability are pain, limitation of abduction, and drooping of the affected shoulder. A detailed knowledge of the course of the nerve and its anatomic relations are essential in avoiding injury. Useful anatomic landmarks are the proximal internal jugular vein in the anterior triangle and Erb's point in the posterior triangle. Prevention of accessory nerve injury is the best management. The indications for lymph node biopsies in the neck should be sound. The use of a general anesthetic without paralysis is recommended if an excisional biopsy is necessary. Adequate exposure is essential. Whether the nerve needs to be identified in all cases has to be individualized and requires careful judgment. A divided or injured nerve is best managed with primary repair within 3 months of injury.     

The spinal accessory nerve distal to the posterior triangle.

Thirty cadaver necks were dissected to determine the course of the accessory nerve distal to the posterior triangle. The nerve was found to have a constant course on the deep surface of the trapezius muscle. This has clinical implications for surgery in the region.     

颈7神经根后股与副神经移位吻合重建斜方肌功能

目的探讨一种根治性颈淋巴清扫术（radical neck dissection，RND）中采用神经移位吻合改善术后肩功能的方法。方法1999年3月～2001年2月，10例需行RND的患者，行RND时保留远颅端至斜方肌前缘的副神经，长度〉3cm，待RND完成后，解削分离出C7神经，并将其后股切断，长度3～5cm，在无张力下行两神经端端吻合。患者在术前和术后1、6及12个月行临床的斜方肌功能客观评价及肌电检测。结果经c，神经根后股与副神经移位吻合后，各部肌电恢复率1、6及12个月分别为上部9．8％、68．9％、73．5％；中部4．7％、73．6％、69．4％；下部6．2％、70．5％、70．3％；7例患者上臂外展超过90。，上肢平均最大外展角度超过95。，肌萎缩较轻，均为1～2级，肩外展受限2级7例．3级3例。结论RND中采用C7神经根后股与副神经移位吻合能较好地重建斜方肌功能。供、受区位于同一术区内，仅有一个吻合口，减少手术创伤。C7神经根后股的切断对手臂运动及感觉功能无影响。     

Accessory spinal nerve injury.

In 7 cases of peripheral lesion of the spinal accessory nerve 4 were produced by malignancy, two by iatrogenical resection of lymph nodes, one by an en bloc dissection of the neck for arteriovenous malformation. Incapacity following the injury is quite marked and includes weakness of the sternomastoid and trapezius muscles, as well as pain presumably from traction on the brachial plexus. The importance of avoiding the nerve in surgical intervention in the neck must be strongly emphasized. A review of the literature suggests that in fresh injuries the spinal accessory nerve should be explored and resutured. Our own experience, however, with nerve repair has been disappointing.     

Anterior approach to the cervical spine: surgical anatomy

While performing the anterior approach to the cervical vertebral bodies, injury to important anatomic structures in the vicinity of the dissection represents a serious risk. The midportion of the recurrent laryngeal nerve and the external branch of the superior laryngeal nerve are encountered in the anterior approach to the lower cervical spine. The recurrent laryngeal nerve is vulnerable to injury on the right side, especially if ligation of inferior thyroid vessels is performed without paying sufficient attention to the course and position of the nerve, and the external branch of the superior laryngeal nerve is vulnerable to injury during ligature and division of the superior thyroid artery. Avoiding injury to the recurrent laryngeal nerve (especially on the right side) and superior laryngeal nerve is a major consideration in the anterior approach to the lower cervical spine. The sympathetic trunk is situated in close proximity to the medial border of the longus colli at the C6 level (the longus colli diverge laterally, whereas the sympathetic trunk converges medially). The damage leads to the development of Horner's syndrome with its associated ptosis, meiosis, and anhydrosis. Awareness of the regional anatomy of the sympathetic trunk may help in identifying and preserving this important structure while performing anterior cervical surgery or during exposure of the transverse foramen or uncovertebral joint at the lower cervical levels. Finally, the spinal accessory nerve (embedded in fibroadipose tissue in the posterior triangle of the neck) is prone to injury. Its damage will result in an obvious shoulder droop, loss of shoulder elevation, and pain. Prevention of inadvertant injury to the accessory nerve is critical in the neck dissection.     

Iatrogenic spinal accessory nerve injury in children

Injury to the spinal accessory nerve in the posterior triangle of the neck results in trapezius paralysis and shoulder dysfunction. The most common etiology is iatrogenic and has been reported extensively in adults. We report 3 cases of spinal accessory nerve injury recognized postoperatively in children and discuss the microsurgical treatment, results, and simple strategies to avoid this complication.     

Spinal accessory nerve injury

Injury to the spinal accessory nerve can lead to dysfunction of the trapezius. The trapezius is a major scapular stabilizer and is composed of three functional components. It contributes to scapulothoracic rhythm by elevating, rotating, and retracting the scapula. The superficial course of the spinal accessory nerve in the posterior cervical triangle makes it susceptible to injury. Iatrogenic injury to the nerve after a surgical procedure is one of the most common causes of trapezius palsy. Dysfunction of the trapezius can be a painful and disabling condition. The shoulder droops as the scapula is translated laterally and rotated downward. Patients present with an asymmetric neckline, a drooping shoulder, winging of the scapula, and weakness of forward elevation. Evaluation should include a complete electrodiagnostic examination. If diagnosed within 1 year of the injury, microsurgical reconstruction of the nerve should be considered. Conservative treatment of chronic trapezius paralysis is appropriate for older patients who are sendentary. Active and healthy patients in whom 1 year of conservative treatment has failed are candidates for surgical reconstruction. Studies have shown the Eden-Lange procedure, in which the insertions of the levator scapulae, rhomboideus minor, and rhomboideus major muscles are transferred, relieves pain, corrects deformity, and improves function in patients with irreparable injury to the spinal accessory nerve.     

Endoscopically assisted decompression of the suprascapular nerve in the supraspinous fossa: a cadaveric feasibility study. Laboratory investigation

OBJECT: The suprascapular nerve may become entrapped as it travels deep to the suprascapular ligament, necessitating decompression. The present study was performed to verify the feasibility of a minimally invasive, endoscopically assisted technique for decompressing the suprascapular nerve in the supraspinous fossa. METHODS: The authors performed dissection and decompression of the suprascapular ligament using an endoscopically assisted technique via a 3-cm skin incision in 10 adult cadavers (20 sides). Measurements were also made of the depth from the skin to the suprascapular ligament. RESULTS: A mean depth of 4 cm was necessary to reach the suprascapular ligament from the skin surface. With the authors' approach, no obvious injury occurred to the suprascapular or other vicinal neurovascular structures (such as the spinal accessory nerve and suprascapular vessels). CONCLUSIONS: The results of this cadaveric study demonstrate that access to the suprascapular nerve can be obtained endoscopically via a small suprascapular incision. This approach obviates a large incision, entry into the glenohumeral joint, and reduces the risk of spinal accessory nerve injury in the posterior cervical triangle, or atrophy of the trapezius or supraspinatus muscles from a standard larger dissection. To the authors' knowledge an endoscopically assisted approach to decompressing the suprascapular nerve as it courses deep to the suprascapular ligament has not been reported previously.     

分化型甲状腺癌颈侧区淋巴结清扫术中神经损伤的预防

手术是分化型甲状腺癌颈淋巴结转移的首选治疗方法。由于甲状腺癌预后良好,因而在肿瘤根治的基础上对原有功能的保护愈发重要。颈淋巴结清扫术中易造成舌下神经、下颌缘支、副神经、迷走神经、颈交感神经、颈丛、臂丛等重要神经的损伤而引起术后相应症状,而正确的解剖认知、丰富的手术经验以及熟练的手术技巧是预防分化型甲状腺癌颈侧区淋巴结清扫术中神经损伤的关键。