Trousseau sign

Trousseau sign of latent tetany is elicited by inflating a sphygmomanometer cuff on the upper arm above systolic blood pressure and maintaining it for approximately 3 minutes. In patients with hypocalcemia, this causes ischemia-induced neuromuscular irritability, resulting in carpal spasm: flexion of the wrist and metacarpophalangeal joints, extension of the interphalangeal joints, and adduction of the thumb and fingers (the 'main d'accoucheur' or obstetrician's hand position). This occurs because hypocalcemia lowers the threshold for neuronal depolarization, increasing membrane excitability; the induced ischemia from cuff inflation exacerbates this effect on peripheral nerves. Trousseau sign is more sensitive and specific than Chvostek sign (facial nerve tapping causing facial muscle twitching) for detecting hypocalcemia. Common causes of hypocalcemia include hypoparathyroidism (post-thyroidectomy or autoimmune), vitamin D deficiency, chronic kidney disease, pseudohypoparathyroidism, and acute pancreatitis. Clinically, hypocalcemia can also present with perioral numbness, muscle cramps, tetany, seizures, and prolonged QT interval on ECG. It's important to note that 'Trousseau sign' is a term also used in oncology (Trousseau's syndrome) to describe migratory thrombophlebitis associated with visceral malignancies (especially pancreatic cancer) — a different, unrelated entity from the same eponymous physician (Armand Trousseau). Board exams may test both meanings, so context is key: hand posture with hypocalcemia vs. migratory venous thrombosis with malignancy.