Axillary Nerve Injury

Aka: Axillary Nerve Injury, Axillary Nerve Lesion, Quadrilateral Space Syndrome, Axillary Nerve Compression

1. See Also
   1. Peripheral Nerve Injury
2. Anatomy
   1. Axillary nerve courses around Humerus and through quadrilateral space on the posterior Shoulder
3. Causes
   1. Shoulder Dislocation
   2. Upward pressure from improper crutch use
   3. Repetitive overuse (pitching, swimming)
   4. Humeral Neck Fracture
   5. Surgery (arthroscopy, rotator cuff repair)
4. Symptoms
   1. Arm Fatigue on throwing and other overhead activities
   2. Posterolateral upper arm and shoulder Paresthesias
5. Signs
   1. Weak abduction and external rotation at the Shoulder
6. Diagnostics
   1. Nerve Conduction Studies and EMG
      1. Consider repeating at 3-6 months after treatment
   2. Shoulder MRI
      1. Typically only helpful for evaluation of differential diagnosis (e.g. labral disorder)
      2. Compression of axillary nerve is unlikely to be visualized on MRI
7. Management
   1. Shoulder Range of Motion Exercises with posterior capsule Stretching
   2. Avoid heavy lifting
   3. Sport specific biomechanical modification to prevent reinjury
      1. Physical therapy referral
   4. Surgical indications
      1. Nerve Conduction Studies and EMG with no improvement after 3-4 months conservative therapy
8. Course
   1. Anticipate a 3-6 month course with therapy
9. References
   1. Neal (2010) Am Fam Physician 81(2): 147-55 [PubMed]
   2. Safran (2004) Am Sports Med 32(4): 1063-76 [PubMed]
   3. Silver (2021) Am Fam Physician 103(5): 275-85 [PubMed]