Absent blink reflex suggests lesion in which cranial nerve?

Absent blink reflex suggests lesion in which cranial nerve?

• A. Cranial Nerve II (CN II)
• B. Cranial Nerve IV (CN IV)
• C. Cranial Nerve VI (CN VI)
• D. Cranial Nerve VII (CN VII)

Answer: (D)

Blink reflex relies on the facial nerve to drive the eyelid muscles. When the eye is stimulated, the sensory input travels to the brainstem, and the motor response that closes the eyelid is carried by the facial nerve to the orbicularis oculi. If the facial nerve is damaged, the motor component cannot fire, so the blink reflex is absent on that side. The other nerves listed are involved in vision or extraocular movements, not the eyelid closure reflex. So a lack of blink reflex points to a lesion of the facial nerve.

Blink reflex relies on the facial nerve to drive the eyelid muscles. When the eye is stimulated, the sensory input travels to the brainstem, and the motor response that closes the eyelid is carried by the facial nerve to the orbicularis oculi. If the facial nerve is damaged, the motor component cannot fire, so the blink reflex is absent on that side. The other nerves listed are involved in vision or extraocular movements, not the eyelid closure reflex. So a lack of blink reflex points to a lesion of the facial nerve.