[1] From 1 to 4 percent of normal patients will test positive for Trousseau's sign of latent tetany.

[3][4] This sign may also be observed as a symptom of hyperventilation syndrome as a result of hypocapnia-induced reduction of calcium levels in the blood.

In the absence of blood flow, the patient's hypocalcemia and subsequent neuromuscular irritability will induce spasm of the muscles of the hand and forearm.

The sign is also known as main d'accoucheur (French for "hand of the obstetrician") because it supposedly resembles the position of an obstetrician's hand in delivering a baby.

[6] The sign is named after French physician Armand Trousseau, who described the phenomenon in 1861.