tetany

Tetany is a clinical syndrome of involuntary muscle contractions, cramps, and paresthesias caused by increased neuromuscular excitability. It most often reflects low ionized calcium, but can accompany disturbances such as hypomagnesemia or metabolic alkalosis. Typical findings include carpopedal spasm (Trousseau sign) and facial twitch upon tapping (Chvostek sign), though symptoms may include tingling around the mouth and in the hands or feet.

Most common causes are hypocalcemia from hypoparathyroidism (including post-surgical), vitamin D deficiency, chronic kidney disease, and malabsorption. Severe hypomagnesemia impairs PTH secretion/action and can produce tetany. Hyperventilation-induced tetany results from respiratory alkalosis lowering ionized calcium; other medications and illnesses that disrupt calcium homeostasis can contribute.

Diagnosis relies on clinical signs supported by labs: measure ionized calcium (preferred) and adjust total calcium for albumin, plus magnesium, phosphate, and PTH as indicated. Arterial blood gas may reveal alkalosis. ECG can help assess risk of arrhythmias in hypocalcemia.

Treatment addresses the underlying cause and rapidly stabilizes calcium. In symptomatic hypocalcemia, administer intravenous calcium (eg, calcium gluconate) with cardiac monitoring, and correct magnesium if deficient. Long-term management may include oral calcium and active vitamin D. In hyperventilation, treat the cause and consider temporary calcium support if necessary, with careful monitoring.

Prognosis is typically favorable with prompt correction; recurrence depends on the underlying disorder, such as chronic hypoparathyroidism requiring ongoing therapy.