Unusual organization of the ansa cervicalis: a case report

ABSTRACT

The superior root of the ansa cervicalis is formed by C1 fibers carried by the hypoglossal nerve, whereas the inferior root is contributed by C2 and C3 nerves. We report a rare finding in a 40-year-old male cadaver in which the vagus nerve fused with the hypoglossal nerve immediately after its exit from the skull on the left side. The vagus nerve supplied branches to the sternohyoid, sternothyroid and superior belly of the omohyoid muscles and also contributed to the formation of the superior root of the ansa cervicalis. In this arrangement, paralysis of the infrahyoid muscles may result following lesion of the vagus nerve anywhere in the neck. The cervical location of the vagus nerve was anterior to the common carotid artery within the carotid sheath. This case report may be of clinical interest to surgeons who perform laryngeal reinnervation and neurologists who diagnose nerve disorders.