Classic history and presentation: Patients with SW present with periscapular aching and fatigue and difficulty lifting objects and raising their arm above the head, due to limited ability to abduct and flex the upper extremity. They may have had recent neck or chest wall surgery or trauma, or history of heavy repetitive arm use in sports or occupations. Classically, the patient will present with a visibly protruding scapula, as the weak affected muscle is overpowered by the normal tone of its opponent.
Prevalence: Rare; there is no independent association with age or sex / gender.
- Surgery involving the chest wall (eg, lymph node dissection, mastectomy)
- Occipital lymph node biopsy (spinal accessory nerve crosses the posterior cervical triangle superficially)
- Penetrating trauma to the neck or thorax
- Sports, hobbies, or occupations involving collisions or repetitive throwing and heavy overhead use
- Changes in the bone of the scapula
- Periscapular soft tissue abnormalities
- Gradual / atraumatic onset:
- Acute onset:
- Traumatic muscle avulsion
- Displaced fractures
- Direct nerve injury from traction, compression, penetrating injury, or surgical dissection involving the neck or chest wall
- Medial SW is most often due to lesions of the long thoracic nerve (roots C4-C7) and/or dysfunction of the muscle it innervates, the serratus anterior.
- Lesions to the long thoracic nerve can occur during surgical procedures involving the chest, such as axillary lymph node dissections, mastectomies, or stab wounds.
- Serratus anterior muscle paralysis can also occur with sports and occupations that involve heavy repetitive arm movements.
- Lateral SW is typically caused by dysfunction of the trapezius muscle (innervated by the spinal accessory nerve CN XI) or rhomboid muscles (innervated by the dorsal scapular nerve).
- Lesions to the spinal accessory nerve (CN XI) can occur during neck dissections.