Question:medium
A patient was admitted with skull base trauma. The doctor was testing the marked structure in the image. Which of the following nerves was being tested?
A patient was admitted with skull base trauma. The doctor was testing the marked structure in the image. Which of the following nerves was being tested?
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After skull base trauma, look for which nerve exits through the jugular foramen and is tested by the gag reflex and posterior pharyngeal sensation.
Updated On: Jun 23, 2026
- Vagus
- Facial nerve
- Glossopharyngeal nerve
- Trigeminal nerve
Show Solution
The Correct Option is C
Solution and Explanation
Anatomical identification: The image shows lateral head-neck dissection in a skull base trauma patient. The marked structure is the glossopharyngeal nerve (CN IX).
CN IX key facts:
- Exits skull via: jugular foramen
- Motor: stylopharyngeus (only muscle)
- Sensory: posterior 1/3 tongue (taste + general), pharynx, soft palate, middle ear
- Parasympathetic: parotid gland via lesser petrosal nerve and otic ganglion
- Autonomic: carotid sinus (baroreceptor), carotid body (chemoreceptor)
Clinical testing of CN IX:
- Gag reflex (afferent limb = CN IX; efferent limb = CN X)
- Taste on posterior 1/3 of tongue
- Sensation of posterior pharyngeal wall
Skull base trauma relevance: Jugular foramen fractures damage CN IX, X, XI (Vernet syndrome). The patient here has skull base trauma and the doctor is testing CN IX.
Why not others?
- Facial nerve: exits stylomastoid foramen; tested by facial movements
- Vagus: also at jugular foramen but more inferior; tested by phonation and swallowing
- Trigeminal: exits via superior orbital fissure/foramen rotundum/ovale; tested by facial sensation \[\boxed{\text{Glossopharyngeal nerve (CN IX)}}\]
CN IX key facts:
- Exits skull via: jugular foramen
- Motor: stylopharyngeus (only muscle)
- Sensory: posterior 1/3 tongue (taste + general), pharynx, soft palate, middle ear
- Parasympathetic: parotid gland via lesser petrosal nerve and otic ganglion
- Autonomic: carotid sinus (baroreceptor), carotid body (chemoreceptor)
Clinical testing of CN IX:
- Gag reflex (afferent limb = CN IX; efferent limb = CN X)
- Taste on posterior 1/3 of tongue
- Sensation of posterior pharyngeal wall
Skull base trauma relevance: Jugular foramen fractures damage CN IX, X, XI (Vernet syndrome). The patient here has skull base trauma and the doctor is testing CN IX.
Why not others?
- Facial nerve: exits stylomastoid foramen; tested by facial movements
- Vagus: also at jugular foramen but more inferior; tested by phonation and swallowing
- Trigeminal: exits via superior orbital fissure/foramen rotundum/ovale; tested by facial sensation \[\boxed{\text{Glossopharyngeal nerve (CN IX)}}\]
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