Tetanie

Tetanie, also known as tetany, is a neuromuscular syndrome characterized by increased nerve and muscle excitability, leading to involuntary muscle contractions, cramps, tingling, and sometimes painful spasms. It most often arises from low levels of ionized calcium in the blood but can also occur with alkalosis, low magnesium, or other metabolic disturbances. Clinically, it may present with carpopedal spasm, facial twitching, and generalized cramps; severe cases can involve laryngospasm or seizures.

Causes and pathophysiology: Hypocalcemia is the most common cause, frequently due to hypoparathyroidism (surgical removal or autoimmune destruction of the parathyroid glands), vitamin D deficiency, chronic kidney disease, pancreatitis, malabsorption, or certain medications. Alkalosis or acute respiratory alkalosis increases calcium binding to albumin and reduces ionized calcium, triggering symptoms. Hypomagnesemia can induce or worsen hypocalcemia by impairing PTH release and action. Transfusion of citrated blood and certain genetic disorders can also contribute.

Diagnosis: Evaluation relies on clinical signs plus laboratory tests. Ionized calcium is preferred over total calcium; corrected calcium may be used when ionized measurements are unavailable. Additional tests include magnesium, phosphate, albumin, and arterial blood gas to assess alkalosis. An electrocardiogram may show QT interval prolongation in hypocalcemia.

Treatment: Acute management aims to restore calcium levels and treat the underlying cause. For severe hypocalcemia, intravenous calcium gluconate is given carefully with cardiac monitoring. Magnesium repletion is necessary if deficient. Long-term management may involve oral calcium and active vitamin D (calcitriol) or vitamin D supplementation, addressing mineral deficiencies, and treating the underlying condition. Prognosis depends on prompt correction and control of the root cause.