Correct Answer: A. Tympanic branch of the glossopharyngeal nerve
The tympanic branch of the glossopharyngeal nerve (CN IX) is the sensory nerve of the pharynx and tonsils. In tonsillitis, inflammation of the palatine tonsils triggers referred pain via this nerve's sensory fibers. The tympanic branch (Jacobson's nerve) carries visceral sensory afferents from the pharyngeal mucosa and tonsils to the nucleus tractus solitarius in the medulla. This same nerve also carries sensory fibers from the middle ear (tympanic plexus), creating an anatomical basis for referred otalgia (ear pain) during pharyngeal inflammation. The glossopharyngeal nerve's sensory distribution to both the pharynx and middle ear explains why patients with tonsillitis commonly report ear pain—a classic referred pain pattern taught in Indian medical schools. This is the most direct and physiologically accurate explanation for otalgia in tonsillitis, making it the discriminating answer in NEET PG.
Why the other options are wrong
B. Auricular branch of the vagus nerve — The auricular branch of the vagus nerve (CN X) supplies the external ear and auricle, not the pharynx or tonsils. While the vagus nerve does innervate the pharynx (motor and some sensory), its auricular branch does not carry sensory fibers from the tonsils. This is a common NBE trap—pairing the vagus with ear innervation without recognizing that CN IX (not CN X) is responsible for referred otalgia in tonsillitis. C. Greater auricular nerve — The greater auricular nerve is a branch of the cervical plexus (C2, C3) that supplies the skin of the external ear and auricle. It has no connection to the pharynx or tonsils and does not carry visceral sensory fibers. This option tests whether students confuse somatic (skin) innervation of the ear with visceral (organ) referred pain pathways—a classic NEET PG distractor. D. Auriculotemporal nerve — The auriculotemporal nerve is a branch of the trigeminal nerve (CN V3) supplying the skin of the temporal region and external ear. It has no role in pharyngeal or tonsillar innervation. This option exploits the fact that CN V does supply the soft palate (via CN V2), but the auriculotemporal branch itself does not—another anatomical distractor designed to confuse cranial nerve distributions.
High-Yield Facts
- Glossopharyngeal nerve (CN IX) is the sensory nerve of the pharynx, tonsils, and posterior third of tongue.
- Jacobson's nerve (tympanic branch of CN IX) carries sensory fibers from both the pharynx and middle ear, explaining referred otalgia in tonsillitis.
- Referred pain in tonsillitis occurs because CN IX innervates both the inflamed tonsil and the middle ear—a classic example of visceral referred pain.
- Vagus nerve (CN X) innervates the pharynx motorically and carries some sensory fibers, but its auricular branch does not mediate tonsillar referred pain.
- Greater auricular nerve (C2, C3) supplies only the skin of the external ear—somatic, not visceral, innervation.
Mnemonics
CN IX = Pharynx + Ear Pain CN IX = 9 = Pharynx (sensory) + Tympanic plexus (middle ear). When pharynx inflames → referred pain to ear via same nerve. Remember: 'Nine = Pharynx + Tympanum.' Referred Pain Rule in Tonsillitis If a nerve innervates BOTH the inflamed organ AND the referred pain site, it's the answer. CN IX does both (pharynx + middle ear) → CN IX is correct. Use this rule to eliminate options that innervate only the ear skin (greater auricular, auriculotemporal).
NBE Trap
NBE pairs "ear pain" with multiple ear-innervating nerves (vagus, greater auricular, auriculotemporal) to lure students into choosing a nerve that supplies the external ear rather than recognizing that referred pain in tonsillitis requires a nerve innervating BOTH the pharynx and middle ear—only CN IX qualifies.
Clinical Pearl
In Indian clinical practice, a child with tonsillitis presenting with otalgia is a routine presentation in pediatric OPD. The ear pain resolves once tonsillitis is treated because the referred pain pathway (CN IX) is no longer stimulated—this bedside observation reinforces that CN IX, not peripheral ear nerves, mediates the pain.
_Reference: Bailey & Love Ch. 38 (Pharynx); Robbins Ch. 16 (Referred Pain Pathways)_