Chvostek sign


Chvostek sign is contraction of facial muscles provoked by lightly tapping over the facial nerve anterior to the ear as it crosses the zygomatic arch. This induces twitching of the homolateral facial muscles due to hyperexcitability of the nerve. Chvostek sign is observed in hypocalcaemic states, such as hypoparathyroidism and the respiratory alkalosis associated with hyperventilation.

There may be concurrent posturing of the hand, known as main d’accoucheur because of its resemblance to the posture adopted for manual delivery of a baby. (see Trousseau sign)

The pathophysiology of this mechanosensitivity of nerve fibres is uncertain, but is probably related to increased discharges in central pathways. Although hypocalcaemia might be expected to impair neuromuscular junction transmission and excitation-contraction coupling (since Ca 2+ ions are required for these processes) this does not in fact occur.


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Physician in training. German translator and lover of medical history.

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