The authors present a unique and unreported variation of the ansa cervicalis, which was found during upper neck microdissection on an isolated cadaveric neck. The C1 contribution to the hypoglossal nerve was found to take its origin from the suboccipital nerve. This branch pierced the dura along with the vertebral artery to enter the intradural space and join the spinal accessory nerve. These fibers then left the spinal accessory nerve and entered the vagus nerve through an anastomosis at the level of the jugular foramen. Subsequently, they departed from the inferior vagal ganglion at the origin of its pharyngeal branch to transiently join the hypoglossal nerve before leaving it as the descendens hypoglossi. The descendens hypoglossi then fused with the vagus nerve to form a common nerve trunk approximately at the level of common carotid artery bifurcation and superior border of the thyroid cartilage. The common nerve trunk coursed anterior to the common carotid artery. The inferior root of the ansa cervicalis, which normally joins the descendens hypoglossi, was absent.
Mohammadali M. Shoja, Pediatric Neurosurgery, Children's Hospital, Birmingham, Alabama, USA