Intra-Scalenus, Intramuscular Long Thoracic Nerve Variant Is Associated with Medial Scapular Winging on Thoracic Outlet Patients: Clinical and Anatomical Study
Madi El Haj, MD1, Ori Safran, MD2, Sofia Anastasia Vorobeitchik, Medical Student3, Tal Eliav, Medical Student4 and Shaul Beyth, MD2, 1Hadassah Hebrew University medical school, Jerusalem, Israel, 2Hadassah Medical Center, Jerusalem, Israel, 3Hadassah Hebrew University Medical Center, Jerusalem, Jerusalem, Israel, 4Ben-Gurion University, Beer Sheva, Israel, Israel
Introduction: The long thoracic nerve (LTN) originates from the cervical spinal roots c5-6-7-8 with variability and traverse the scalenus medius muscle. Compressive neuropathy of the LTN causes medial scapular winging. Scalenus muscles hypertrophy and fibrosis is associated with thoracic outlet syndrome (TOS). We aimed to investigate the prevalence of preoperative medial scapular winging in TOS patients and its correlation with the anatomical variation of LTN scalenus root.
Materials & Methods: A retrospective review was conducted between January 2019-June 2023, including 71 patients: 40 with Neurogenic TOS (NTOS) and 31 patients with Venous TOS (VTOS) (Table 1) who underwent a thoracic outlet decompression first rib resection utilizing supra and para-clavicular approaches, respectively. Preoperative medial scapular winging was evaluated based on clinical observation of the medial and inferior scapular borders for winging or prominence, lack of smooth coordinated movement with early scapular elevation or during arm forward flexion, and rapid downward rotation during arm descent from full flexion. Intraoperatively, prior to middle scalenectomy, the LTN was carefully dissected and electrically stimulated, with recordings of photographs and videos of the anatomical variants. Intramuscular and extramuscular LTN classification was based on passage of the major LTN trunk relative to the middle scalene muscle. Further subclassification was based on the root contribution variance (Figure 1). Data analysis of LTN variant prevalence and correlation with preoperative medial winging was done using chi-square test.
Results: Medial scapular winging was observed in 37.5% with NTOS and in 29% with VTOS. Two groups were characterized: Extramuscular and intramuscular types with subclassifications (1A, 1B, 2A, 2B, 3A, 3B, 4, 5A, 5B,6 ). Intramuscular type was observed in 32.5% and 16.1% in NTOS and VTOS, respectively (Table 2). Scapular winging was observed in 94% of the intramuscular group vs 13% of the extramuscular group. Highly significant correlation was observed between LTN intramuscular variant and scapular winging within the 71 TOS patients as well as within the NTOS and VTOS separately (p=0.000).
Conclusions: Intramuscular LTN is associated with preoperative scapular winging in patients with TOS. Great care should be taken during middle scalenectomy to avoid iatrogenic LTN injury.
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