Study of the formation and distribution of the ansa cervicalis and its clinical significance

The ansa cervicalis is a neural loop in the neck. It is formed by the union of two main nerve roots -i.e., superior and inferior- derived from the ventral rami of the cervical nerves. The aim of this study was to explore the anatomical variations of the ansa cervicalis with a view to preventing accidental injury during surgical procedures. Fifty formalin-fixed cadavers were dissected bilaterally for the ansa cervicalis, in which abnormalities were observed in three cadavers. In one cadaver, the ansa cervicalis was absent and the strap muscles of the neck received their innervations from the vagus nerve. Two cadavers displayed an ansa cervicalis formed by the superior root, which branched out from the vagus nerve instead of the hypoglossal nerve. In recent years, there has been an abundance of techniques utilizing the ansa cervicalis to reinnervate the paralyzed larynx. Because of its proximity to major nerves and vessels of the neck, a good understanding of the topography and morphology of this loop is essential. Any variation in the course, contributing roots or branching pattern of the ansa cervicalis, potentially modifies and complicates the course of procedures relating to this nerve.