Eliciting Chvostek’s sign

Chvostek's sign is contraction of the muscles of the eye, mouth or nose, elicited by tapping along the course of the facial nerve. The examiner taps gently over the facial nerve in front of the ear.

This sign usually suggests hypocalcemia but can occur normally in about 25% of patients. Typically, it precedes other signs of hypocalcemia and persists until the onset of tetany. It can’t be elicited during tetany because of strong muscle contractions.
Normally, eliciting Chvostek's sign is attempted only in patients with suspected hypocalcemic disorders. However, because the parathyroid gland regulates calcium balance, Chvostek's sign may also be tested in patients before neck surgery to obtain a baseline.