Chvostek sign is elicited by tapping which nerve?

• A. Trigeminal nerve CN V
• B. Facial nerve CN VII
• C. Glossopharyngeal CN IX
• D. Vagus CN X

Answer: (B)

Chvostek sign is produced by tapping the facial nerve as it runs superficially over the cheek near the parotid gland. In low calcium states, nerves become more excitable, so a light tap on this nerve triggers visible contractions of the ipsilateral facial muscles. This characteristic facial twitching occurs specifically with tapping the facial nerve, rather than other nerves, making it the classic sign.