A posterior fossa craniotomy damages the glossopharyngeal nerve (CN IX). Which specific reflex is MOST reliably lost?

• A Gag reflex (afferent limb via CN IX, efferent via CN X)
• B Corneal reflex
• C Carotid sinus reflex (afferent via Hering's nerve, efferent via CN X) ✓
• D Jaw jerk reflex

Explanation

The carotid sinus reflex afferent limb is carried by Hering's nerve (sinus nerve of Hering), a branch of CN IX, which carries baroreceptor signals from the carotid sinus to the nucleus tractus solitarius. The efferent limb is via CN X and the vagal cardiac branches. This reflex controls heart rate and blood pressure in response to carotid sinus pressure. The gag reflex is also CN IX afferent but requires specific posterior pharyngeal wall stimulation. The corneal reflex is CN V/VII; jaw jerk is CN V5.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.