Tetany (medical sign)

Tetany
Classification and external resources
ICD-10	R29.0
ICD-9-CM	781.7
DiseasesDB	29143
MeSH	D013746
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Tetany or tetany seizure is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disease or other conditions that increase the action potential frequency of muscle cells or the nerves that innervate them. Muscle cramps which are caused by the disease tetanus are not classified as tetany; rather, they are due to a lack of inhibition to the neurons that supply muscles.

French Professor Armand Trousseau (1801-1867) devised the trick (now known as the Trousseau sign of latent tetany) of occluding the brachial artery by squeezing, to trigger cramps in the fingers. Also, tetany can be demonstrated by tapping anterior to the ear, at the emergence of the facial nerve. A resultant twitch of the nose or lips suggests low calcium levels. This is now known as the Chvostek sign.

Tetany is characterized by contraction of distal muscles of the hands (carpal spasm with extension of interphalangeal joints and adduction and flexion of the metacarpophalangeal joints) and feet (pedal spasm) and is associated with tingling around the mouth and distally in the limbs.

EMG studies reveal single or often grouped motor unit discharges at low discharge frequency during tetany episodes.

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