Chvostek's sign

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Chvostek's sign (also Weiss' sign) is one of the signs of tetany seen in hypocalcemia.

It refers to an abnormal reaction to the stimulation of the facial nerve. When the facial nerve is tapped at the angle of the jaw, the facial muscles on the same side of the face will contract momentarily (typically a twitch of the nose or lips) because of hypocalcaemia and hyperexcitability of nerves.

It was first described by František Chvostek, an Austrian physician in 1876, and later independently by Nathan Weiss in 1883.

Though classically described in hypocalcaemia, this sign may also be encountered in respiratory alkalosis, such as that seen in hyperventilation.

Trousseau's sign is also often used to detect early tetany.