Signs in acute hypocalcemia

Q: Which sign is more specific to acute hypocalcemia? (select one)

A) Chvostek's sign 

B) Trousseau's sign 

Answer: B

Chvostek's sign can be elicited by tapping the facial nerve just anterior to the ear, resulting in contraction of the ipsilateral facial muscles. It mostly manifests as twitching of the lip or spasm of all facial muscles. The severity of contraction correlates well with the severity of the hypocalcemia. Chvostek's sign is not specific for hypocalcemia as it can occur in about 10 percent of the normal population.

Trousseau's sign can be elicited by inflating the sphygmomanometer above systolic blood pressure for three minutes, resulting in adduction of the thumb, flexion of the metacarpophalangeal joints, extension of the interphalangeal joints, and flexion of the wrist. The sphygmomanometer above systolic blood pressure should not be raised more than three minutes as excitability of the nerve trunk is maximum at three minutes and returns to normal even if ischemia is maintained for more than three minutes.

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References:

1. Cooper MS, Gittoes NJ. Diagnosis and management of hypocalcaemia. BMJ 2008; 336:1298.

2. Thakker RV. Hypocalcemia: Pathogenesis, differential diagnosis, and management. In: Primer on the metabolic bone diseases and disorders of mineral metabolism, 6th ed, Favus MJ (Ed), American Society of Bone and Mineral Research, Washington, DC 2006. p.213.