Accessory Nerve Injury

Overview

This StatPearls review by AlShareef and Newton, last updated in December 2022, covers injury to the accessory nerve (cranial nerve XI). Because the nerve is long and lies close to the surface in the neck, it is easily injured. The trapezius and sternocleidomastoid are its main targets, and the spinal accessory nerve is the part most often affected.

Causes and frequency

Most injuries are iatrogenic: lymph node biopsy in the posterior triangle (3 to 8% injury rate), neck dissection, tumour or vascular surgery in the neck, and cosmetic surgery. Injury after neck dissection is more frequent with radical dissection than with modified or nerve-sparing procedures. Other causes include penetrating or blunt trauma, sports injuries, traction, tumours at the jugular foramen and neurologic disease.

Presentation and evaluation

The main symptoms are pain and weakness around the shoulder, which may spread to the upper back, neck and arm. Signs include asymmetry, a drooping shoulder, reduced abduction and scapular winging that is worst with abduction, which distinguishes it from long thoracic nerve injury. Limited motion can progress to adhesive capsulitis. Diagnosis can be difficult because the trapezius has a dual nerve supply. Electromyography and nerve conduction studies are not required for diagnosis but are useful for serial monitoring and for planning treatment. Ultrasound shows the nerve and muscle atrophy but cannot detect transection.

Management

Mild injuries with improving function can be managed with medical treatment (NSAIDs, nerve blocks, nerve stimulation) and rehabilitation, with early and extended physical therapy that keeps passive range of motion. Surgery is considered for dense paralysis, no improvement on serial EMG or examination, troubling pain or dysfunction, or a nerve in continuity that does not respond to stimulation. Options are neurolysis, primary repair, cable grafting and the Eden-Lange muscle transfer, which is recommended for spontaneous trapezius palsy or symptoms lasting over 20 months. A transected nerve needs urgent reconstruction.

Prognosis

Outcomes depend on the cause, the extent of injury, radiation, the delay before repair and graft length. Recovery after repair takes about 4 to 10 months, and early referral and operation give the best results.