Variants of the intermediate supraclavicular nerve: a cadaveric case series and clinical implications

The supraclavicular nerves (SCNs) are sensory branches of the cervical plexus that may exhibit clinically important anatomical variations. Variants involving transosseous clavicular passage may predispose individuals to nerve entrapment and increase the risk of iatrogenic injury during clavicular surgery. This cadaveric case series describes three unusual variations of the intermediate supraclavicular nerve (ISCN).

Nine formalin-fixed adult cadavers (comprising five males and four females; mean age, 79.1 years; median age, 78 years; age range, 69-91 years) were examined between 2024 and 2026 at the Department of Anatomy and Surgical Anatomy, Aristotle University of Thessaloniki, with one sufficiently preserved supraclavicular region assessed per cadaver. The contralateral regions of the three variant cases could not be reliably evaluated because embalming- related tissue alterations hindered precise dissection. The SCNs were identified along the posterior border of the sternocleidomastoid muscle and traced distally toward the clavicle. In cases suspected of transosseous variants, the clavicle was sectioned sagittally to verify intraclavicular nerve passage.

Variations were identified in 3 of 9 cadavers (3 of 9 examined sides); this descriptive proportion should not be interpreted as an estimate of population prevalence. Case 1 demonstrated an unusually long distal course of the ISCN and medial supraclavicular nerve (MSCN), extending into the anterior thoracic wall superior to the mammary papilla. Case 2 demonstrated intraclavicular passage of the ISCN through a clavicular tunnel, confirmed by sagittal clavicular sectioning. Case 3 demonstrated clavicular perforation by an atypical secondary common trunk that divided into medial and intermediate terminal branches after emerging inferior to the clavicle.

These findings expand the known anatomical spectrum of the ISCN and emphasize the marked variability of its distal course and branching pattern. Recognition of such variants is important because they may predispose to nerve entrapment and increase the risk of iatrogenic injury during clavicular surgery, fracture fixation, and related surgical procedures involving the clavicular region.