The deep communicating branches of the cervical plexus originate from a loop between the ventral rami of C1 and C2, which give rise to branches, which communicate with the vagus (X cranial nerve) and hypoglossal nerves (XII cranial nerve) and the sympathetic trunk; branches also connect the ventral rami of C4 and C5.  Fibers that pass to the hypoglossal nerves later give rise to a meningeal branch, the superior root of the ansa cervicalis and the nerves to the thyrohyoid and geniohyoid muscles.  

Supply
Deep communicating branches of the cervical plexus contribute to the supply of the sternothyroid, sternohyoid, omohyoid, thyrohyoid and geniohyoid muscles.