You anesthetize the base of a lesion on the lateral border of the tongue for biopsy. Which sensory nerve is being anesthetized?

Correct answer: D. Lingual nerve

• A. The chorda tympani carries taste and secretomotor fibers only; it does not carry general sensation on its own.
• B. The glossopharyngeal nerve (CN IX) supplies general sensation AND taste to the POSTERIOR one-third of the tongue and mediates the gag reflex.
• C. The hypoglossal nerve (CN XII) is purely MOTOR to the tongue muscles — anesthetizing it would not eliminate pain.
• D. CORRECT. The LINGUAL NERVE, a branch of V3, provides GENERAL SENSATION (touch, pain, temperature) to the anterior two-thirds of the tongue, the floor of the mouth, and the lingual gingiva. It also carries chorda tympani fibers (special taste for the anterior two-thirds, and parasympathetic secretomotor fibers to the submandibular and sublingual glands). Local infiltration at the base of an anterior/lateral tongue lesion blocks lingual nerve terminals.

Note: Tongue innervation grid — anterior 2/3: general = lingual (V3), taste = chorda tympani (VII). Posterior 1/3: both general and taste = glossopharyngeal (IX).