The Trousseau sign is a clinical finding, not a disease. It is an indicator of an underlying state of increased neuromuscular irritability known as latent tetany. This sign, named after the 19th-century French physician Armand Trousseau, manifests as an involuntary muscle contraction in the hand and fingers. Its presence suggests an electrolyte imbalance and helps providers identify a state that might otherwise go unnoticed.
Eliciting the Trousseau Sign
To check for the Trousseau sign, a healthcare professional uses a sphygmomanometer, more commonly known as a blood pressure cuff. The cuff is placed around the patient’s upper arm and inflated to a pressure about 20 mmHg higher than their systolic blood pressure. This pressure, which temporarily cuts off blood flow through the brachial artery, is maintained for up to three minutes.
A positive Trousseau sign is the development of a specific hand spasm called a carpopedal spasm. This spasm has a distinct appearance: the wrist flexes, the large knuckles (metacarpophalangeal joints) flex, and the fingers extend at the middle and end joints (interphalangeal joints). The thumb pulls in toward the palm, a position known as adduction. The resulting posture is sometimes called “main d’accoucheur,” a French term meaning “obstetrician’s hand,” due to its resemblance to the hand position used during childbirth. Once the spasm is observed, the cuff is deflated.
Underlying Physiological Cause
The cause of the Trousseau sign is directly linked to low levels of calcium in the blood, a condition called hypocalcemia. Calcium ions play a role in the nervous system by stabilizing voltage-gated sodium channels in nerve cell membranes. These channels are responsible for initiating the electrical signals that cause muscles to contract. The presence of adequate calcium makes it more difficult for these channels to open, preventing spontaneous nerve activity.
When blood calcium levels are low, this stabilizing effect is diminished. The threshold needed to activate the sodium channels is lowered, making nerve cells hyperexcitable and more likely to fire. During the test, inflating the blood pressure cuff causes ischemia, a restriction in blood supply to the forearm and hand. This lack of blood flow further irritates the excitable nerves, triggering the characteristic carpopedal spasm.
Associated Medical Conditions
The Trousseau sign points toward various medical issues that cause hypocalcemia. The most frequent cause is hypoparathyroidism, a condition where the parathyroid glands do not produce enough parathyroid hormone (PTH). PTH is a primary regulator of blood calcium levels, so its deficiency leads directly to hypocalcemia. This can occur if the glands are damaged during thyroid surgery, due to an autoimmune disease, or from genetic factors.
Other conditions can also result in low calcium levels. Severe vitamin D deficiency is a cause, as vitamin D is necessary for the body to absorb calcium from the intestines. Chronic kidney disease can impair the activation of vitamin D and the excretion of phosphate, disrupting calcium balance. Less commonly, acute pancreatitis and malabsorption syndromes that prevent proper nutrient absorption can lead to hypocalcemia.
The Chvostek Sign
Another clinical indicator of latent tetany is the Chvostek sign. A healthcare provider elicits this by gently tapping on the facial nerve at a point just in front of the ear. A positive response is a twitching of the facial muscles on the same side of the face, often visible at the corner of the mouth or nose.
The Chvostek sign is a complementary finding to the Trousseau sign, which is regarded as a more specific and sensitive indicator. The Trousseau sign is present in about 94% of individuals with hypocalcemia. The Chvostek sign may be absent in up to a third of patients with the condition and can be present in a small percentage of people with normal calcium levels.