Nasal cavity innervation is derived from two branches of the trigeminal nerve (V), the ophthalmic (V1) and the maxillary (V2). The anterior ethmoid nerve (from V1) innervates the anterior aspects of the nasal cavity and septum. The posterior nasal cavity and septum are innervated primarily by the lateral posterior superior, lateral inferior posterior, and nasopalatine nerves of V2.

The sensory innervation of the oral cavity and muscles of mastication derive from the mandibular branch of the trigeminal nerve (V3). Muscles of the tongue are supplied primarily by the hypoglossal, CN XII. Its general sensory path is from the lingual nerve, a branch of V3, for the anterior two thirds, and by the glossopharyngeal nerve, CN IX, for the posterior one third. The hard and soft palate are innervated by the greater and lesser palatine nerves, respectively, which are branches from V2.

Sensory innervation of the entire pharynx and epiglottis is supplied primarily by the glossopharyngeal nerve, CN IX, and motor nerve supply is
from the vegas nerve, CN X. The superior laryngeal nerve, derived from the vegas nerve, CN X, supplies sensory to the larynx above the true vocal cords as well as to the cricothyroid muscle. The recurrent laryngeal nerve, also from the vegas, CN X, supplies all other muscles of the larynx and sensation at the level of vocal cords and below. Recurrent laryngeal nerve also supplies sensory and motor components to the trachea.

Several protective reflexes can be elicited with airway manipulation, including gag, glottic closure (laryngospasm), and cough. These reflexes can be blocked by either their afferent (sensory) and/or efferent (motor) components. Input for the gag reflex is the glossopharyngeal nerve, CN IX, and output is the vegas, CN X. Fibers for glottic closure reflex are superior laryngeal for afferent and both superior and recurrent laryngeal for efferent. Other reflexes that may also be encountered are bronchospasm reflex, secretory reflex, vomiting reflex, and cardiovascular reflex.

Anesthetization of the airway for awake fiber-optic intubation can be achieved by a number of techniques and can be adjusted to the patient, the operator preference, and availability of supplies (Table 4.1). These often include a mixture of topicalization and nerve blocks. Topicalization methods include direct application of lidocaine or viscous lidocaine, aerosol spray, atomization, or nebulization (Table 4.2). Common nerve blocks include glossopharyngeal, superior laryngeal, and translaryngeal. Other blocks may be performed, such as maxillary and mandibular nerve blocks. However, these are more invasive with a lower risk/benefit ratio, and their relevant terminal nerves can easily be blocked topically.