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The Chvostek Sign and the Trousseau Sign

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By Ashesh

A 45-year-old woman presented with a two-day history of diarrhea, vomiting, progressive numbness around her mouth and generalized body cramps. She had undergone a total thyroidectomy for a multinodular goiter seven months back. Her vital signs were stable. Trousseau sign was evidenced a few seconds after the sphygmomanometer cuff was inflated to more than the systolic blood pressure on the left upper arm. What is the most likely diagnosis?
Diagnosis is at the end of the article but first let's answer these questions
          what is Trousseau sign? 
  and what is Chvostek sign?

Signs of Hypocalcemia
The Chvostek Sign is a clinical sign of existing nerve hyperexcitability (tetany) seen in hypocalcemia. It refers to an abnormal reaction to the stimulation of the facial nerve. When the facial nerve is tapped in front of tragus the facial muscles on the same side of the face will contract momentarily (typically a twitch of the nose or lips) because of hypocalcemia with resultant hyperexcitability of nerves.
Though classically described in hypocalcemia, this sign may also be encountered in respiratory alkalosis, such as that seen in hyperventilation, which causes decreased serum Ca2+ with a normal calcium level due to a shift of Ca2+ from the blood to albumin which has become more negative in the alkalotic state.
The Chvostek sign in hypocalcemia can be seen in cases of
hypoparathyroidism,
pseudohypoparathyroidism,
hypovitaminosis D.
The Chvostek sign may also be present in hypomagnesemia. Magnesium is a cofactor for Adenylate cyclase. The reaction that Adenylate cyclase catalyzes is 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.


 
 video embeeded from NEJMvideo youtube channel.

Trousseau Sign of latent tetany is a medical sign observed in patients with low calcium. This sign may be positive before other manifestations of hypocalcemia such as hyperreflexia and tetany, as such it is generally believed to be more sensitive than the Chvostek sign for hypocalcemia.
To elicit the sign, a blood pressure cuff is placed around the arm and inflated to a pressure greater than the systolic blood pressure and held in place for 3 minutes. This will occlude the brachial artery. 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 wrist and metacarpophalangeal joints flex, the DIP and PIP joints extend, and the fingers adduct. 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.

The most likely diagnosis in above case is  iatrogenic hypoparathyroidism.






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