A 65-year-old man comes to the office with a 4-month history of persistent left ear pain that is slowly worsening. He is also having some difficulty swallowing. The patient has no chronic medical conditions but has smoked 1 pack of cigarettes per day for the last 46 years. On examination, the external auditory canal is patent and the tympanic membrane is clear with no middle ear effusion. There is an enlarged lymph node in the left anterior neck. Flexible fiberoptic laryngoscopy reveals an ulcerative mass on the posterior pharyngeal wall of the hypopharynx. Involvement of which of the following nerves is most likely responsible for this patient's ear pain?
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This patient has otalgia in the setting of a normal ear examination, which is likely referred pain (pain perceived at a different site than its true origin). Further evaluation shows an ulcerative mass in the hypopharynx with an enlarged lymph node, which is consistent with mucosal head and neck squamous cell carcinoma (HNSCC).
Many sources of pain in the head and neck can be referred to the ear because several cranial nerves also innervate parts of the ear. Common causes of referred ear pain include temporomandibular joint disease, dental disease, or cancer affecting the tongue base, hypopharynx, or larynx.
This patient's referred otalgia is most likely due to his hypopharyngeal carcinoma causing irritation of the vagus nerve (CN X). The vagus nerve has afferent fibers innervating the larynx and hypopharynx and also has a branch that provides afferent sensory input from the external auditory canal. Similarly, the glossopharyngeal nerve (CN IX), which innervates the upper pharynx and base of tongue, also provides sensory innervation to the external auditory canal and can contribute to referred otalgia from tumors in these areas.
(Choices A, B, and F) The trigeminal nerve (CN V) provides sensory innervation for much of the face, including parts of the ear. The facial nerve (CN VII) and great auricular nerve (originates from C2 and C3) innervate portions of the external auditory canal. Although these nerves carry sensation from the ear, they do not provide innervation to the hypopharynx.
(Choice C) The vestibulocochlear nerve (CN VIII) contributes special sensory (hearing, balance) from the ear but does not contribute to general sensation. Therefore, lesions that impact the vestibulocochlear nerve tend to cause hearing loss or imbalance (eg, vertigo) rather than pain.
(Choice E) The hypoglossal nerve (CN XII) innervates the muscles of the tongue. It has motor function only, so dysfunction tends to produce weakness (eg, deviation of the tongue) rather than pain.
Educational objective:
Referred otalgia is common in head and neck pathology because many cranial nerves innervate the ear (eg, CN V, VII, IX, X). In particular, tumors in the hypopharynx, larynx, or base of tongue cause referred otalgia due to sensory contributions from the glossopharyngeal and vagus nerves.