mouth to the zygomatic process gives rise to only a contraction of the muscles of the mouth and nose. Causes Chvostek's sign is found in tetany. However, it may also be present in hypomagnesemia. Magnesium is a cofactor for adenylate cyclase, which catalyzes the conversion of ATP to 3',5'-cyclic AMP. The 3',5'-cyclic AMP (cAMP) is required for parathyroid hormone activation. It is frequently seen in alcoholics, persons with diarrhea, patients taking aminoglycosides or diuretics, because hypomagnesemia can cause hypocalcemia. It is also seen in measles, tetanus and myxedema. It can also be found in subjects with respiratory alkalosis, for example as a result of hyperventilation syndrome, which can lead to a drastic reduction of the concentration in serum of calcium ions while at normal levels, for the binding of a significant proportion of ionized calcium (Ca2+) with albumin and globulins. Clinical significance Chvostek's sign is not a very specific sign of tetany as it may be seen in 10% to 25% of healthy adults. It is therefore not a reliable clinical sign for diagnosing latent tetany. The sensitivity is lower than that in the corresponding Trousseau sign as it is negative in 30% of patients with hypocalcemia. Due to the combination of poor sensitivity and specificity the clinical utility of this sign is reduced. References External links František Chvostek Nathan Weiss Symptoms and signs: Endocrinology, nutrition, and metabolism