Patient Safety: Mononeuropathies in Scapular Winging

Published April 03, 2025

Practice

From the Quality and Patient Safety Committee

A 38-year-old male is referred for electrodiagnostic evaluation of left shoulder weakness. Further history reveals that prior to the weakness, he had a brief period of severe left shoulder pain that started without trauma although he does think that the pain started soon after receiving a vaccination. Physical examination reveals the left scapula is positioned medially with downward rotation as compared to the right side. Forward flexion of the left shoulder demonstrates decreased active range of motion and a heightened prominence of the medial border of the scapula (aka “scapular winging”).

Question: Which ONE of the following nerves would most likely be involved with this clinical presentation?

A. Dorsal scapular nerve
B. Long thoracic nerve
C. Axillary nerve
D. Spinal accessory nerve

Explanation: 

Mononeuropathies are a small but clinically significant cause of scapular dyskinesis and altered resting position. Scapular winging, characterized by abnormal prominence of the medial or inferior scapular border during shoulder motion, most commonly results from long thoracic nerve (LTN) palsy (55%) or spinal accessory nerve (SAN) palsy (30%). Neuralgic amyotrophy, a leading cause of both, can be triggered by various factors, including vaccination.

The serratus anterior, innervated by the LTN, originates from ribs 1–9 and inserts on the medial scapular border. It depresses, protracts, and upwardly rotates the scapula. LTN or serratus anterior dysfunction causes “medial winging,” where the scapula shifts medially with downward rotation at rest, worsening with forward flexion or pushing against resistance.
The trapezius, innervated by the SAN, elevates, retracts, and upwardly rotates the scapula. SAN or trapezius injury leads to “lateral winging,” with the scapula resting in a depressed, lateral, and downwardly rotated position, which becomes more pronounced during active shoulder abduction.
While physical exams help differentiate scapular winging causes, electrodiagnostic testing provides greater insight into neurologic and neuromuscular etiologies and prognosis. Scapular winging is a clinical sign associated with various neuromuscular and musculoskeletal conditions, but LTN and SAN palsies remain the most common. These mononeuropathies can often be distinguished on clinical exam based on medial or lateral scapular positioning.


Authors: Daniel Pierce, MD;  David Del Toro, MD

Sources:

  1. Didesch JT, Tang P. Anatomy, Etiology, and Management of Scapular Winging. J Hand Surg Am. 2019;44(4):321-330. doi:10.1016/j.jhsa.2018.08.008
  2. Kibler WB, Ludewig PM, McClure PW, Michener LA, Bak K, Sciascia AD. Clinical implications of scapular dyskinesis in shoulder injury: the 2013 consensus statement from the 'Scapular Summit'. Br J Sports Med. 2013;47(14):877-885. doi:10.1136/bjsports-2013-092425
  3. Seror P, Lenglet T, Nguyen C, Ouaknine M, Lefevre-Colau MM. Unilateral winged scapula: Clinical and electrodiagnostic experience with 128 cases, with special attention to long thoracic nerve palsy. Muscle Nerve. 2018;57(6):913-920. doi:10.1002/mus.26059
  4. Shields LBE, Iyer VG, Zhang YP, Burger JT, Shields CB. Parsonage-Turner Syndrome Following COVID-19 Vaccination: Clinical and Electromyographic Findings in 6 Patients. Case Rep Neurol. 2022;14(1):58-67. Published 2022 Feb 15. doi:10.1159/000521462

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