QS Study


Tetany is generally considered to result from very low calcium levels in the blood. When the ECF conc. of Ca2+ falls below normal the nervous system becomes progressively more and more excitable resulting into an extensive spasm of skeletal muscle. It is a situation that is indicated by symptoms like tremors, spasms, and muscular cramps.


The situation is mostly brought about by a combination of symptoms that occur due to a low level of calcium. Excitation occurs due to increase neural membrane permeability of Na+, Tetany usually develops when plasma Ca2+ conc reaches 6 mg/dl, (40% below normal). It is lethal at about 4 mg/d1.

Signs and symptoms of can include:

  • Tingling or burning in your fingertips, toes, and lips
  • Muscle aches or cramps in your legs, feet, abdomen or face
  • Twitching or spasms of your muscles, particularly around your mouth,
  • Painful menstruation

Clinical feature

In children:

(1) Carpopedal syndrome

  • Metacarpophalangeal joints are flexed,
  • Interphalangeal joints of fusion and thumbs are extended,
  • An opposition of thumbs.

(2) Stridor – It is caused by spasm of glottis asphyxia.

(3) Convulsion.

In adults

  • Tingling in the hands, feet and around the mouth,
  • Painful carpopedal spasm – less often,
  • Stridor and fits – rare.

Latent tetany

It may be present when signs of overt tetany are lacking. It is best to recognize by eliciting –

  1. Trousseau’s sign: Spasm of upper extremities cause the flexion of wrist and thumb with an extension of a finger.
  2. Chvostek’s sign: A quick contraction of an ipsilateral facial muscle when taping over the facial nerve.