Anatomic Variations of the Ansa Cervicalis Involving the Vagus and Hypoglossal Nerves: New Observations Expanding Jelev Classification.

BACKGROUND AND OBJECTIVES: The ansa cervicalis exhibits considerable anatomic variability, particularly in its connections with the vagus and hypoglossal nerves. Understanding these variations is essential for surgical procedures involving the neck region. METHODS: Anatomic dissection of 23 formalin-fixed human cadavers, including the analysis of 46 cervical plexuses, was performed between 2018 and 2025. Five cases demonstrating atypical neural configurations were documented and compared with Jelev classification. RESULTS: Five anatomic variants of the ansa cervicalis were identified, representing a significant complement to Jelev classification. Two cases corresponded to Type III, with the presence of additional nerve bundles and atypical connections with the vagus nerve, permitting the distinction between the classical variant (IIIa) and the complex variant (IIIb). Two additional cases corresponded to Type V and one to Type II. Previously undescribed connections were observed between the vagus, hypoglossal, and sympathetic nerves, suggesting additional pathways of innervation for the infrahyoid muscles. CONCLUSION: The findings expand the Jelev classification and highlight the compensatory role of the vagus nerve. These variations have important clinical implications for head and neck reconstructive and microsurgical procedures.