Interconnected Anatomy and Clinical Relevance of the Dorsal Scapular and Long Thoracic Nerves: A Donor Study

Background: The dorsal scapular nerve (DSN) and the long thoracic nerve (LTN) exhibit variable anatomical pathways, which may contribute to upper back pain and impaired scapular movement in affected patients. This study investigates these variations to enhance clinicians’ diagnostic and surgical approaches. Methods: The bilateral cervical regions of 32 formalin-embalmed donors (64 sides) were dissected to document the origin of the DSN, the relationship with the scalene muscles of the DSN, and anatomical connections between the DSN and LTN. Measurements of the distance between the mastoid process and the piercing point of the DSN to the scalene muscle were obtained with digital calipers. Additional measurements were obtained from the medial border of the scapula at two specific locations: the scapular spine (zone 1) and the midpoint between the scapular spine and the inferior angle of the scapula (zone 2). Results: The DSN demonstrated four distinct cervical spinal nerve root origins and five unique scalene muscle piercing patterns. The average distance between the DSNs’ scalene muscle piercing point and the mastoid process was 94.87 ± 10.09 mm, with significantly greater distances observed in male donors compared to female donors (p < 0.001). Connections between the DSN and LTN were identified in 65.2% of the examined cervical regions. The mean distance of the DSN from the medial border of the scapula at zone 2 was significantly greater than at zone 1 (p < 0.001). Conclusions: The anatomical variation findings and classification of the DSN provide valuable insights, offering guidance for conducting clinical procedures of the scalene and rhomboid musculature in a way that minimizes the risk of iatrogenic injury. The documented variations may also assist in the diagnosis and management of DSN-related pathologies such as DSN neuropathy.