Does injury to the spinal accessory nerve (CN 11) cause scapular winging?

Spinal Accessory Nerve (CN XI) Injury and Scapular Winging

Yes, injury to the spinal accessory nerve (CN XI) causes lateral scapular winging due to trapezius muscle dysfunction, resulting in decreased shoulder abduction, shoulder pain, cosmetic disfiguration, and disability. 1, 2

Anatomy and Function of CN XI

• The accessory nerve consists of a small cranial root originating from the nucleus ambiguus within the medulla oblongata and a large spinal root originating from the ventral horn of the spinal cord between C1 and C5 levels 1
• CN XI supplies portions of the sternocleidomastoid muscle and the upper portion of the trapezius muscle 1
• The trapezius is a major scapular stabilizer composed of three functional components that contribute to scapulothoracic rhythm by elevating, rotating, and retracting the scapula 2

Clinical Presentation of CN XI Injury

• Weakness and atrophy of the trapezius muscle causes lateral scapular winging 1
• Patients present with an asymmetric neckline, a drooping shoulder, winging of the scapula, and weakness of forward elevation 2
• The shoulder droops as the scapula is translated laterally and rotated downward 2
• This condition can be painful and disabling, affecting quality of life 1, 2

Common Causes of CN XI Injury

• Iatrogenic injury (most common) - following surgical procedures like lymph node biopsy or during internal jugular vein cannulation 1, 2
• Trauma to the posterior cervical triangle where the nerve has a superficial course 2
• Deep tissue massage (rare) 3
• Intracranial lesions affecting the nerve origin 4

Diagnostic Evaluation

• Complete electrodiagnostic examination is recommended 2
• MRI is the preferred imaging modality as it offers superior soft tissue contrast to demonstrate denervation changes and directly image features of neuritis 1
• MRI can visualize the entire course of CN XI, including intracranial, high cervical, and extracranial portions 1
• Contrast-enhanced CT neck may be useful to characterize lesions along the extracranial course of CN XI and demonstrate atrophy of the trapezius muscle 1

Treatment Options

• Conservative management is appropriate initially and for older sedentary patients 2
• If diagnosed within 1 year of injury, microsurgical reconstruction of the nerve should be considered 2
• For chronic trapezius paralysis unresponsive to 1 year of conservative treatment, surgical reconstruction is indicated for active patients 2
• The Eden-Lange procedure (transfer of levator scapulae, rhomboideus minor, and rhomboideus major muscles) is effective for relieving pain, correcting deformity, and improving function 2, 5
• A modified Eden-Lange procedure may be used for chronic lateral winging of the scapula 6
• In cases of intracranial accessory nerve injury, suprascapular nerve release at the level of the scapular notch can effectively treat shoulder and periscapular pain 4

Outcomes After Surgical Treatment

• Tendon transfer procedures have shown significant improvement in shoulder function scores, forward elevation, and pain reduction 5
• The Eden-Lange procedure has demonstrated improvement in American Shoulder and Elbow Surgeons Shoulder scores (from 33.3 to 64.6), forward elevation (from 141.7° to 151.0°), and pain scores (from 7.0 to 2.3 on visual analog scale) 5

Clinical Pearls and Pitfalls

• Delayed diagnosis is common and can lead to chronic disability 2
• Extended delays from time of injury to surgery may necessitate muscle transfers rather than nerve repair 6
• Scapular winging may impose traction on other soft tissues of the shoulder region, including the suprascapular nerve, causing additional pain 4
• Comprehensive evaluation of the entire course of the nerve is essential as lesions can occur anywhere from the brainstem to the trapezius muscle 1