For a biopsy of a hairy tongue lesion located in the posterior third of the tongue, which nerve must be considered regarding anesthesia?

Correct answer: D. Glossopharyngeal nerve (CN IX)

• A. The facial nerve (CN VII) supplies taste to the anterior 2/3 of the tongue via the chorda tympani; it does not provide sensation to the posterior tongue.
• B. The vagus nerve (CN X) provides sensation to the epiglottis and larynx; it contributes minor sensation to the very base of the tongue but CN IX is the primary nerve for the posterior third.
• C. The trigeminal nerve (lingual branch of V3) provides general sensation to the anterior 2/3 of the tongue; not the posterior third.
• D. Correct. The glossopharyngeal nerve (CN IX) provides both general sensation and taste to the posterior one-third of the tongue. A biopsy of the posterior tongue requires consideration of CN IX for anesthesia.