Definition of Tetany

Tetany: A combination of signs and symptoms, due usually to low calcium, that can include:

• Hyperreflexia (overactive neurological reflexes),
• Carpopedal spasm (spasms of the hands and feet),
• Cramps, and
• Laryngospasm (spasm of the larynx, the voice box).

Tetany characteristically is considered to result from a severe degree of hypocalcemia (literally, very low calcium levels in the blood). It can also result from reduction in the ionized fraction of plasma calcium without marked hypocalcemia, as occurs in severe alkalosis (when the blood is highly alkaline). Although the calcium that is typically measured in laboratory medicine is the calcium in blood plasma, what really causes tetany is low ionic calcium in the extracellular fluid (between cells) and intracellular fluid (within cells).

Tetany is characterized by sensory symptoms consisting of paresthesias (odd feelings) of the lips, tongue, fingers and feet; carpopedal spasm, which may be prolonged and painful; generalized muscle aching; and spasms of facial musculature.

Tetany and tetanus sound alike and are easily confused. They both come from the same root, namely, from the Greek "tetanos" meaning convulsive tension. However, tetanus (lockjaw) is a specific disease marked by painful tonic muscular contractions caused by the toxin (tetanospasmin) made by the bacteria Clostridium tetani that acts upon the central nervous system.