Which cranial nerve is tested by asking a patient to smile?

Which cranial nerve is tested by asking a patient to smile?

• A. Facial nerve
• B. Trigeminal nerve
• C. Olfactory nerve
• D. Optic nerve

Answer: (A)

Smiling checks the motor function of the facial nerve (cranial nerve VII), which innervates the muscles of facial expression like the zygomaticus major. When you ask someone to smile, you’re assessing whether these muscles can contract symmetrically and strength is preserved. Normal, symmetric elevation of the corners of the mouth indicates intact facial motor function; weakness or asymmetry points to facial nerve impairment, such as facial nerve palsy. The other nerves have different roles: the trigeminal nerve mainly handles facial sensation and chewing muscles, the olfactory nerve handles sense of smell, and the optic nerve handles vision.

Smiling checks the motor function of the facial nerve (cranial nerve VII), which innervates the muscles of facial expression like the zygomaticus major. When you ask someone to smile, you’re assessing whether these muscles can contract symmetrically and strength is preserved. Normal, symmetric elevation of the corners of the mouth indicates intact facial motor function; weakness or asymmetry points to facial nerve impairment, such as facial nerve palsy.

The other nerves have different roles: the trigeminal nerve mainly handles facial sensation and chewing muscles, the olfactory nerve handles sense of smell, and the optic nerve handles vision.