Tetany: A Comprehensive Medical Guide

Overview

Tetany is a clinical syndrome characterized by involuntary muscle contractions (spasms) that usually begin in the hands and feet and can spread to the face, neck, and trunk. The underlying problem is typically an abnormal increase in the excitability of nerves and muscles, most often caused by low calcium levels (hypocalcemia) or an imbalance in other electrolytes such as magnesium and potassium.

Although tetany can affect people of any age, it is most common in:

• Adults with chronic kidney disease, parathyroid disorders, or malabsorption syndromes.
• Newborns and infants with prematurity or vitamin D deficiency.
• Patients taking certain medications (e.g., loop diuretics, bisphosphonates, anticonvulsants).

Exact prevalence data are limited because tetany is usually a symptom of an underlying condition rather than a standalone diagnosis. However, hypocalcemia— the most frequent cause—affects roughly 1–2 % of the general population, and about 15–20 % of patients with chronic kidney disease develop severe hypocalcemia that can precipitate tetany (National Kidney Foundation, 2023).

Symptoms

Symptoms can range from subtle paresthesias to severe, painful muscle cramps. The classic signs include:

Neuromuscular signs

• Paresthesia – tingling or “pins‑and‑needles” sensation, usually around the mouth, fingertips, and toes.
• Carpopedal spasm – forced flexion of the wrists and fingers, giving a “hand of benediction” appearance.
• Facial twitching – especially around the mouth and eyelids (facial or perioral spasms).
• Muscle cramps – painful, involuntary contractions of the calves, abdomen, or back.
• Positive Trousseau sign – a delayed onset of spasm when a blood pressure cuff is inflated on the arm for 3 minutes.
• Positive Chvostek sign – twitching of the facial muscles after tapping the facial nerve at the cheek.

Cardiovascular and respiratory signs

• Palpitations or irregular heartbeat (due to electrolyte disturbances).
• Shortness of breath or a feeling of “tightness” in the chest.
• Rarely, bronchospasm leading to wheezing.

General symptoms

• Muscle weakness or fatigue.
• Anxiety or a sense of impending doom (often secondary to the discomfort).
• Seizure‑like activity in severe hypocalcemia.

Causes and Risk Factors

While tetany itself is a symptom, identifying the underlying cause is essential for treatment.

Common causes

• Hypocalcemia – most frequent cause; may result from:
  • Parathyroid hormone (PTH) deficiency (hypoparathyroidism) or resistance.
  • Vitamin D deficiency or malabsorption.
  • Renal failure (impaired conversion of vitamin D to its active form).
• Hypomagnesemia – low magnesium can worsen hypocalcemia by impairing PTH secretion.
• Alkalosis – especially respiratory alkalosis, which increases calcium binding to albumin, lowering ionized calcium.
• Medications – loop and thiazide diuretics, bisphosphonates, phenytoin, and certain chemotherapy agents.
• Pancreatitis – saponification of calcium in the abdomen reduces serum calcium.

Risk factors

• Chronic kidney disease (CKD) or dialysis dependence.
• Previous neck surgery (risk of accidental removal of parathyroid glands).
• Malabsorption disorders (celiac disease, inflammatory bowel disease, gastric bypass).
• Low dietary calcium or vitamin D intake.
• Pregnancy and lactation – increased calcium demand.
• Genetic disorders affecting calcium metabolism (e.g., DiGeorge syndrome).

Diagnosis

Diagnosis is a stepwise process that combines a thorough history, physical examination, and targeted laboratory testing.

History & Physical Exam

• Ask about recent surgeries, medication changes, kidney disease, and dietary habits.
• Look for classic signs: Chvostek and Trousseau.
• Assess for underlying systemic disease (e.g., autoimmune disorders).

Laboratory tests

Additional studies (when indicated)

• Electrocardiogram (ECG) – prolonged QT interval is a hallmark of hypocalcemia.
• Imaging – neck ultrasound or sestamibi scan if parathyroid adenoma is suspected.
• Genetic testing – for rare hereditary hypocalcemia syndromes.

Treatment Options

Treatment focuses on rapid correction of the electrolyte disturbance and addressing the root cause.

Acute management

• Intravenous calcium gluconate (10 mL of 10 % solution) administered over 10 minutes can relieve severe spasms within minutes. Continuous cardiac monitoring is recommended.
• If the patient is conscious and able to swallow, oral calcium carbonate or calcium citrate (1–2 g elemental calcium) can be used for milder cases.
• Correct accompanying magnesium deficiency** with IV magnesium sulfate (1–2 g over 15 minutes) because low magnesium may blunt the response to calcium.