Chvostek sign is elicited by tapping which nerve?

• A. Trigeminal nerve
• B. Glossopharyngeal nerve
• C. Accessory nerve
• D. Facial nerve

Answer: (D)

Chvostek sign reflects increased neuromuscular irritability from low calcium. It is produced by tapping the facial nerve as it courses near the parotid gland, just in front of the ear. The tap triggers twitching of the ipsilateral facial muscles, especially around the mouth and eye, because hypocalcemia makes peripheral nerves more excitable and motor endplates fire with mild stimulation. The facial nerve is responsible for the muscles of facial expression, so tapping in this region directly elicits these contractions. Tapping other nerves wouldn’t produce this characteristic facial twitching pattern, since they innervate different regions and muscles.