Imaging Studies

High-resolution ultrasonography (HRUS) allows visualization of the normal SAN, as well as changes after accessory nerve injury. The SAN appears as a singular small (approximately 1 cm in diameter on ultrasound), hypoechoic tubular structure in the transverse plane and as a hypoechoic linear structure in the longitudinal plane. It is best identified in the posterior cervical triangle. In addition, HRUS is able to demonstrate hyperechoic and atrophic changes in the trapezius muscle, granuloma formation, and scar entrapment of the SAN in the region of the injury and the normal course of the nerve beyond. However, the actual transection of the SAN is not readily visualized by HRUS.^[9]

A retrospective study by Powell et al indicated that, preoperatively, SAN injuries can more accurately be characterized by ultrasonography than by magnetic resonance imaging (MRI). SAN injuries in the study, most of which were iatrogenic, were surgically confirmed as stump neuromas and incomplete nerve injuries. The investigators determined that 95% of the preoperative ultrasonography reports, versus 24% of those derived from MRI, agreed with the surgical diagnosis.^[39] However, ultrasonography is operator dependent, so when ultrasonographic results are in doubt, MRI should still be considered.

Electrodiagnostic tests

Electrodiagnostic tests are most sensitive for the detection of nerve conduction impairment.^[2]

Nerve conduction studies reveal prolonged latencies in nerve injury, while electromyography (EMG) may reveal signs of denervation or reinnervation, depending on the timing of the study.^[20]

Electrophysiologic integrity of the SAN does not correlate well with the clinical symptoms and outcome measures for shoulder dysfunction.^[3]

However, EMG has shown a positive correlation with range-of-motion (ROM) tests, particularly active shoulder abduction with contralateral head rotation as a test of strength. Consequently, this physical examination maneuver serves as a reliable and cost-effective tool for evaluating the degree of upper trapezius denervation.

Electrodiagnostic tests can be used in the management of SAN injury as follows:

To monitor upper trapezius recovery of function
To plan a physical therapy course to reduce postoperative morbidity^[2]
To confirm suspicions of SAN trauma that are related to traction or stretch injury of the nerve
To monitor the SAN nerve intraoperatively for identification and preservation^[3]

A retrospective study by Kim et al indicated that in a nerve conduction study of the SAN, the best recording site for the upper trapezius “is the midpoint between the C7 spinous process and the acromion,” while the optimal recording site for the middle trapezius is “the junction of middle and lateral thirds of the line between the root of scapular spine and the vertebral spine.”^[40]

Some patients with severe SAN injury do not experience the degree of dysfunction that one would expect from their evaluations by EMG. In contrast, patients treated with nerve-sparing neck procedures often present with symptoms and signs suggestive of nerve impairment. These apparently contradictory results can be explained by the influence of several factors, including age, gender, dominant hand, presence of concurrent myopathy or neuropathy, condition of other synergistic shoulder girdle muscles, preoperative or postoperative radiotherapy, and anatomic variations of SAN contributions to trapezius muscle innervation.^{[15, 41]}

Clinical evaluation of shoulder function

Clinical evalution of shoulder function includes the following:

ROM assessment by goniometry to evaluate flexion and abduction of the shoulder joint
Manual measure of muscle strength in the motions of elevation, flexion, and abduction ^[4]

The constant shoulder scale is as follows:

This weighted test takes 10 minutes to perform and combines patient symptom scores (35%) and objective measures of active shoulder function (65%) and is a validated clinical assessment with established accuracy across many diseases that affect the shoulder.
Scores range from 0-100, with higher scores indicating better shoulder function.^[42]

The disease-specific quality-of-life (QOL) questionnaires are sensitive tools to evaluate shoulder function. Some more common questionnaires that have been validated for shoulder specific evaluations include the following:

The University of Washington QOL scale – shoulder domain
The neck dissection impairment index
The shoulder disability questionnaire (SDQ)^[43]

Intraoperative diagnosis is intuitive. A provoked movement of the shoulder in response to cautery or dissection must be carefully reviewed. Clinically examining the patient’s motor function postoperatively is best; in addition, widely explore the area during surgery to rule out an inadvertent injury.^[14]

Treatment & Management

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Media Gallery

Course of the spinal accessory nerve (SAN) in the posterior cervical triangle. DG = posterior belly of digastric muscle; T = trapezius; LS = levator scapulae; IJV = internal jugular vein; black arrow = SAN.
Shoulder orthosis for scapulohumeral alignment.
Relationship of internal jugular vein to the spinal accessory nerve (SAN).
Spinal accessory nerve (SAN) posterior to the internal jugular vein.
Eden-Lange procedure.
Surgical landmarks for the identification of the spinal accessory nerve (SAN).
Shoulder syndrome.
Spinal accessory nerve (SAN) traversing a bifurcated internal jugular vein (IJV). (* = carotid artery, yellow arrow = SAN)
Algorithm for management of spinal accessory nerve (SAN) injury.
Surgical management for spinal accessory nerve (SAN) injury and preoperative delay in diagnosis.

of 10

Author

Rohan R Walvekar, MD Clinical Professor, Mervin L Trail Endowed Chair in Head and Neck Oncology, Director, Salivary Endoscopy Service, Co-Director, ENT Service, Department of Otolaryngology-Head and Neck Surgery, University Medical Center, Louisiana State University Health Sciences Center

Rohan R Walvekar, MD is a member of the following medical societies: American Head and Neck Society, Association of Otolaryngologists of India

Disclosure: Received royalty from Hood Laboratories for consulting; Received consulting fee from Cook Industries for consulting; Received consulting fee from Medtronic Xomed for consulting.

Coauthor(s)

Neelam P Phalke, MD Resident Physician, Department of Otolaryngology-Head Neck Surgery, Louisiana State University Health Sciences Center

Neelam P Phalke, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Ted L Tewfik, MD Professor of Otolaryngology-Head and Neck Surgery, Professor of Pediatric Surgery, McGill University Faculty of Medicine; Senior Staff, Montreal Children's Hospital, Montreal General Hospital, and Royal Victoria Hospital

Ted L Tewfik, MD is a member of the following medical societies: American Society of Pediatric Otolaryngology, Canadian Society of Otolaryngology-Head & Neck Surgery

Disclosure: Nothing to disclose.

Chief Editor

Arlen D Meyers, MD, MBA Professor of Otolaryngology, Dentistry, and Engineering, University of Colorado School of Medicine

Arlen D Meyers, MD, MBA is a member of the following medical societies: American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, American Head and Neck Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cerescan; Ryte; Neosoma; MI10<br/>Received income in an amount equal to or greater than $250 from: Neosoma; Cyberionix (CYBX)<br/>Received ownership interest from Cerescan for consulting for: Neosoma, MI10.

Additional Contributors

Jaime R Garza, MD, DDS, FACS Consulting Staff, Private Practice

Jaime R Garza, MD, DDS, FACS is a member of the following medical societies: Alpha Omega Alpha, American Academy of Otolaryngology-Head and Neck Surgery, American College of Surgeons, American Society for Aesthetic Plastic Surgery, American Society of Maxillofacial Surgeons, Texas Medical Association, Texas Society of Plastic Surgeons

Disclosure: Received none from Allergan for speaking and teaching; Received none from LifeCell for consulting; Received grant/research funds from GID, Inc. for other.

Kristin B Gendron, MD Consulting Staff, Midwest ENT Specialists

Kristin B Gendron, MD is a member of the following medical societies: Alpha Omega Alpha

Disclosure: Nothing to disclose.

Ryan J Li, MD Resident Physician, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins Hospital and Health System

Ryan J Li, MD is a member of the following medical societies: Alpha Omega Alpha, Christian Medical and Dental Associations

Disclosure: Nothing to disclose.

Duncan Hanby, MD Resident Physician, Department of Otolaryngology and Head and Neck Surgery, Louisiana State University School of Medicine

Duncan Hanby, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Head and Neck Society, American Medical Association

Disclosure: Nothing to disclose.

Acknowledgements

The author would like to thank Dr. A.K. D’Cruz, MS, DNB, Professor and Chairman, Head/Neck Surgery, Tata Memorial Hospital, Mumbai, India, for Image 7, and Dr. Umamaheshwar Duvvuri, MD, PhD, Fellow, Head/Neck Surgery, MD Anderson Cancer Center, Houston, Texas, for Image 8.