(Kiosk 2) Late Presentation of Iatrogenic Spinal Accessory Neuropathy

Case Diagnosis: Left Spinal Accessory Neuropathy with Associated Rotator Cuff Tendinopathy

Case Description: A 66-year-old male with a history of type-1 diabetes presented with 9 months of left posterolateral neck and upper trapezius region pain without inciting event. Examination demonstrated atrophy of the left upper trapezius and significant left lateral winging of the scapula. A small, healed surgical incision was also noted at the left lateral neck, where patient reported he had prior surgery during infancy for removal of a “cyst”. His presenting pain was provoked on exam with rotator cuff maneuvers. Manual motor testing found 5/5 strength in all muscle groups except 4/5 left shoulder abduction and rightward head turning.

Discussion: Isolated spinal accessory neuropathy is a well-known iatrogenic complication following surgical procedures in the posterior triangle of the neck, less commonly seen with sports and trauma-related injury. Damage to the spinal accessory nerve (SAN) typically results in trapezius weakness and scapular dysfunction. However, these findings may be masked given the dynamic characteristics of the shoulder joint.

Setting: Physical Medicine & Rehabilitation Clinic; Electromyography Lab

Assessment/Results: Electrodiagnostic testing was performed and found evidence of chronic, severe left spinal accessory neuropathy. Diagnostic ultrasound demonstrated left upper trapezius atrophy and left levator scapula hypertrophy. CT findings from 9 years prior showed similar findings. The patient was diagnosed with rotator cuff tendinopathy in the setting of chronic spinal accessory neuropathy from presumed brachial cyst surgery during infancy. His pain improved with physical therapy focused on scapular stabilization and rotator cuff strengthening.

Conclusion: This case describes a late presentation of symptoms secondary to spinal accessory neuropathy. Although injury to the SAN likely occurred during a surgical procedure from infancy, compensatory actions of other shoulder muscle groups masked any symptoms from this nerve injury for many decades. The diagnosis of this neuropathy likely would not have been noted without careful physical examination.