Block of the glossopharyngeal nerve is required for manipulations of the posterior third of the tongue and pharyngeal wall. Structures more distal in the airway to the epiglottis will require block of vagal branches.
If there is one set of regional blocks that an anesthesiologist should master, it is airway blocks. Even those anesthesiologists who prefer to use general anesthesia for the majority of their cases will be faced with the need to provide airway blocks before anesthetic induction in patients who may have airway compromise, trauma to the upper airway, or unstable cervical vertebrae. As illustrated in Fig. 25.1 , innervation of the airway can be separated into three principal neural pathways: trigeminal, glossopharyngeal, and vagus. If nasal intubation is planned, some method of anesthetizing the maxillary branches from the trigeminal nerve will need to be carried out. Because manipulations involve the pharynx and posterior third of the tongue, glossopharyngeal block will be required. Structures more distal in the airway to the epiglottis will require block of vagal branches.
Specific glossopharyngeal nerves that are of interest to anesthesiologists who undertake airway anesthesia are the pharyngeal nerves, which are primarily sensory to the pharyngeal mucosa; the tonsillar nerves, which provide sensation to the mucosa overlying the palatine tonsil and contiguous parts of the soft palate; and sensory branches to the posterior third of the tongue. The glossopharyngeal nerve exits the skull through the jugular foramen in close contact with the spinal accessory nerve. As the glossopharyngeal nerve exits the jugular foramen, it is also in close contact with the vagus nerve, which likewise travels within the carotid sheath in the upper portion of the neck.
The vagus nerve supplies innervation to the mucosa of the airway from the level of the epiglottis to the distal airways through both the superior and the recurrent laryngeal nerves, as illustrated in Figs. 25.2 and 25.3 . Although the vagus is primarily a parasympathetic nerve, it also contains some fibers from the cervical sympathetic chain, as well as motor fibers to laryngeal muscles. The superior laryngeal nerve provides sensation to the surfaces of the epiglottis and to the airway mucosa to the level of the vocal cords. It provides innervation to the mucosa after entering the thyrohyoid membrane just inferior to the hyoid bone between the greater and the lesser cornua of the hyoid. This mucosal innervation is carried out through the internal laryngeal nerve, a branch of the superior laryngeal nerve. The superior laryngeal nerve also continues as the external laryngeal nerve along the exterior of the larynx; it provides motor innervation to the cricothyroid muscle.