Vagus, Accessory, and Hypoglossal Nerves

This chapter reviews the anastomoses of the vagus, accessory, and hypoglossal nerves. The anastomoses between the glossopharyngeal and vagus nerves can be divided into two classes: direct communications involving the main trunks or ganglia; and indirect connections involving their branches. The pharyngeal, intercarotid, and carotid sinus plexuses originate from the glossopharyngeal and vagus nerves and cervical sympathetics. The hypoglossal nerve may have a dorsal root bearing a ganglion and it may also exit from the posterior surface of the medulla oblongata. It can innervate the mylohyoid, digastric, or stylohyoid muscles. The term spinal accessory nerve plexus has been used to denote the communications between the spinal accessory nerve and branches from other lower cranial and upper cervical nerves. The spinal accessory nerve may occasionally be absent, in which case the trapezius muscle is solely supplied by the cervical spinal nerve branches.