Which cranial nerve primarily tests the corneal reflex?

Which cranial nerve primarily tests the corneal reflex?

• A. Cranial Nerve VII (CN VII)
• B. Cranial Nerve II (CN II)
• C. Cranial Nerve IX (CN IX)
• D. Cranial Nerve X (CN X)

Answer: (A)

The corneal reflex mainly tests the motor output to the eyelid via the facial nerve. When the cornea is touched, the sensation travels through the ophthalmic division of the trigeminal nerve to the brainstem, and the response is eyelid closure driven by the facial nerve (orbicularis oculi). So a normal blink indicates an intact facial motor pathway, while a diminished or absent blink points to facial nerve dysfunction, even if corneal sensation is intact. The other nerves listed don’t mediate this reflex: the optic nerve handles vision, and the glossopharyngeal and vagus nerves aren’t involved in triggering the eyelid-closing response.

The corneal reflex mainly tests the motor output to the eyelid via the facial nerve. When the cornea is touched, the sensation travels through the ophthalmic division of the trigeminal nerve to the brainstem, and the response is eyelid closure driven by the facial nerve (orbicularis oculi). So a normal blink indicates an intact facial motor pathway, while a diminished or absent blink points to facial nerve dysfunction, even if corneal sensation is intact. The other nerves listed don’t mediate this reflex: the optic nerve handles vision, and the glossopharyngeal and vagus nerves aren’t involved in triggering the eyelid-closing response.