Spinal accessory neuropathy

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Lateral neck, with accessory nerve seen between the sternocleidomastoid and trapezius muscles.
  • CN XI which innervates the sternocleidomastoid and trapezius muscles[1]
  • Commonly removed during radical neck dissection for head and neck cancers


  • Iatrogenic
    • Radical or modified neck dissection
  • Trauma
  • Stroke

Clinical Features

  • Trapezius atrophy
  • Weakness of shoulder abduction
  • Scapular dyskinesis

Differential Diagnosis

Peripheral nerve syndromes

  • Upper extremity
    • Ulnar
      • Cause of Injury: Elbow injury.
      • Sensory changes in the 5th and medial half of 4th digits, weak wrist flexors, “claw hand”
    • Radial
    • Median, distal
      • Cause of Injury: Wrist dislocation, laceration, Carpal Tunnel Syndrome
      • Weak flexion of radial half of digits and thumb, loss of abduction and opposition of thumb. Ape hand deformity, benediction sign. Loss of sensation of lateral three and one-half digits and nail beds
    • Median, proximal
    • Musculocutaneous
      • Cause of Injury: Anterior shoulder dislocation, entrapment due to hypertrophy
      • Elbow flexion and supination weakness, radial forearm sensory deficits
    • Axillary
    • Suprascapular
      • Cause of Injury: Paralabral cyst, bone/soft tissue tumor, Scapular fracture, traction injury, Parsonage-Turner syndrome
      • Weak arm abduction to 90 degrees, weak shoulder flexion to 30 degrees, weak internal rotation
  • Lower extremity
    • Femoral
      • Cause of Injury: Pubic rami fracture, pelvic fractures
      • Weak knee extension, anterior knee sensory deficits
    • Obturator
    • Posterior tibial
      • Cause of Injury: Knee dislocation
      • Weak toe flexion, plantar foot sensory deficit
    • Superficial peroneal
      • Cause of Injury: Fibular neck fracture, knee dislocation
      • Weak ankle eversion, lateral dorsal foot sensory deficits
    • Deep peroneal
      • Cause of Injury: Fibular neck fracture, compartment syndrome
      • Sensory deficit at dorsal 1st web space, weak ankle and toe dorsiflexion
    • Sciatic
      • Cause of Injury: Posterior hip dislocation
      • Lower leg weakness, foot drop, leg sensory deficits
    • Superior gluteal
    • Inferior gluteal
      • Cause of Injury: Acetabular pelvic fracture, s/p hip replacement
      • Abnormal gait, gluteus maximus weakness resulting in gluteus maximus lurch


  • Usually a clinical diagnosis
  • Positive scapular flip sign
  • Outpatient EMG or nerve conduction studies


  • NSAIDs
  • Shoulder sling
  • Physical therapy
  • Surgical repair


  • Discharge with neurology follow up

See Also

External Links


  1. Kelley MJ et al. Spinal Accessory Nerve Palsy: Associated Signs and Symptoms. J Orthop Sport Phys. 2008;38(2):78-86.