Cranial Nerves and Swallowing
Cranial nerves important for swallowing include CN V (Trigeminal Nerve), VII (Facial Nerve), IX (Glossopharyngeal Nerve), X (Vagus), XI (Accessory Nerve) , and XII (Hyoglossus Nerve).
Sensory Innervation
Sensory receptors may respond to touch, flow, pressure, and taste (Steele & Miller, 2010). Sensory inputs for swallowing come from CN V, IX, and X. Taste is innervated by CN VII, IX, and X. Cranial nerve VII innervates taste in the anterior 2/3 of the tongue. CN IX innervates taste and sensory function in the the posterior 1/3 of the tongue. CN X innervates taste receptors in the epiglottis region.
Cranial Nerve V: Trigeminal
The mandibular branch of CN V provides sensory input for the anterior 2/3 of the tongue, the mucosa of the cheek, floor of mouth, gums (both upper and lower), temporomandibular joint, lower teeth, and the lower lip. Sensory input from the mucosa of the nasopharynx, soft palate, hard palate, gums, the upper teeth is transported through the maxillary branch. See Box 1.54 for a schematic of CN V.
Box 1.54: Cranial nerve V: Trigeminal
The trigeminal nerve is important for mastication and hyo-laryngeal trajectory.
Clinical Note
Damage to CN V may result in the following.
- Loss of oral sensation leads to reduced bolus control and awareness of bolus location.
- Damage to mandibular branch will reduce mastication skills.
- Reduced function in the floor of mouth (MH & ABD) muscles will reduce hyo-laryngeal trajectory, which may impact epiglottic down-folding and UES opening. The end result may be reduced airway protection during bolus passage in the pharynx, thus increasing the risk of laryngeal penetration. Also, increased risk of residue in either the vallecula or pyriform sinus leads to increased risk of penetration or aspiration after the swallow.
- Damage to tensor veli palatini may reduce velar-pharyngeal valving and lead to nasopharyngeal reflux of material.
Cranial Nerves IX and X: Glossopharyngeus & Vagus
CN IX provides sensory innervation to the posterior 1/3 of the tongue as well as the mucosa of the oropharynx, palatine tonsils, faucial pillars, and temporomandibular joint. The pharyngeal branch of CN X provides sensory innervation for the levator veli palatini muscle as well as the superior and middle pharyngeal constrictor muscles. The internal branch of the superior laryngeal nerve of CN X provides sensory innervation to the mucosa of the epiglottis, the supraglottic region, the laryngeal joint receptors, the aryepiglottic folds, and the posterior tongue. The recurrent laryngeal branch of CN X provides sensory innervation to the mucosa of the subglottic region and the esophagus. The esophageal branch of CN X provides sensory innervation to the esophageal mucosa and striated muscle in the esophagus. See Box 1.56 and 1.57 for schematics of CN IX and X, respectively.
Motor Innervation
Motor function for swallowing is innervated by CN V, VII, IX, X, XI, and XII.
Cranial Nerve V- Trigeminal
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