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. Hypocalcemia: It is the primary cause of tetany. Low ionized calcium levels in the extracellular fluid increase the permeability of neuronal membranes to sodium ion, medical physiology guyton pdf download a progressive depolarization, which increases the possibility of action potentials. This occurs because calcium ions interact with the exterior surface of sodium channels in the plasma membrane of nerve cells.
Hypocalcemia is not a term for tetany but is rather a cause of tetany. The usual cause of tetany is lack of calcium.
Underfunction of the parathyroid gland can lead to tetany. Low levels of magnesium can lead to tetany.
Clostridium tetani toxin, via inhibition of glycine-mediated and GABA-ergic neurotransmission, may lead to tetany. An excess of potassium in grass hay or pasture can trigger winter tetany, or grass tetany, in ruminants. 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. EMG studies reveal single or often grouped motor unit discharges at low discharge frequency during tetany episodes. Severe hyperphosphatemia and hypocalcemia: a dilemma in patient management”. A New Syndrome, Magnesium-Deficiency Tetany”.