Bilateral absence of ansa cervicalis replaced by vagocervical plexus: case report and literature review

The bilateral absence of the ansa cervicalis was discovered during dissection of the neck in an elderly male cadaver. On both sides it was replaced by a vagocervical plexus formed by the vagus nerve and C1 and C2 ventral rami from the cervical plexus. A descending branch from this vagocervical plexus supplied the strap muscles of the neck. From a review of the literature the incidence of bilateral absence of the ansa cervicalis and its replacement by a vagocervical plexus appears to be extremely rare. Morphological variability, embryological basis, and clinical relevance of this uncommon anatomical variant are discussed.