Bell phenomenon is most closely associated with impairment of which cranial nerve?

Bell phenomenon is most closely associated with impairment of which cranial nerve?

• A. Trigeminal nerve
• B. Facial nerve
• C. Acoustic nerve
• D. Vagus nerve

Answer: (B)

Bell phenomenon reflects an eyelid closure problem due to weakness of the orbicularis oculi, the muscle that tightly closes the eyelids. The orbicularis oculi is controlled by the facial nerve, so when this nerve is impaired, eyelid closure is incomplete. As a protective response, the globe tends to roll upward during attempted closure, producing the characteristic Bell phenomenon. This sign is most closely linked to facial nerve palsy. The other nerves listed don’t govern the eyelid closing mechanism, so they don’t produce this phenomenon.

Bell phenomenon reflects an eyelid closure problem due to weakness of the orbicularis oculi, the muscle that tightly closes the eyelids. The orbicularis oculi is controlled by the facial nerve, so when this nerve is impaired, eyelid closure is incomplete. As a protective response, the globe tends to roll upward during attempted closure, producing the characteristic Bell phenomenon. This sign is most closely linked to facial nerve palsy. The other nerves listed don’t govern the eyelid closing mechanism, so they don’t produce this phenomenon.