Muscle cramps and tetany: Chvostek and Trousseau signs
- Sign
Painful muscle spasms, and two bedside signs that reveal over-excitable nerves when blood calcium is low.
See it in 3D: Facial nerve (VII) · Facial nerve branches · Median nerve · Ulnar nerve · Parathyroid glands
What it is
A cramp is a sudden, painful contraction of one muscle, often the calf at night, that eases with stretching. Tetany is different: nerves become over-excitable, usually because ionized calcium is low, and fire on their own, causing tingling around the mouth and in the fingers and spasms of the hands and feet. The Chvostek and Trousseau signs bring out latent tetany at the bedside.
The anatomy it tests
- Chvostek tests the excitability of the facial nerve (cranial nerve VII) as it crosses the face in front of the ear.
- Trousseau tests the median and ulnar nerves of the forearm, made ischemic by the cuff, which increases their excitability.
- The parathyroid glands, behind the thyroid, keep blood calcium stable through parathyroid hormone.
- Low extracellular calcium lowers the firing threshold of nerve membranes, so they discharge spontaneously.
How to elicit it
- Ask about tingling around the mouth, fingers and toes, hand or foot spasms, recent neck surgery, hyperventilation, diarrhea or vomiting.
- Chvostek: with the patient's face relaxed and mouth slightly open, tap the facial nerve just in front of the ear, below the cheekbone (zygomatic arch).
- Chvostek is positive when the muscles of the same side of the face twitch: the corner of the mouth, and with a stronger response the nose and eyelid.
- Trousseau: place a blood pressure cuff on the upper arm and inflate it above the systolic pressure.
- Keep the cuff inflated for up to about three minutes while watching the hand, then deflate it.
- Trousseau is positive when carpal spasm appears: wrist and knuckles flexed, fingers straight and together, thumb drawn into the palm.
- Note whether the spasm is painful, and record both signs as positive or negative.
What a positive result means
- Positive signs suggest low ionized calcium: hypoparathyroidism (especially after thyroid or parathyroid surgery), vitamin D deficiency, chronic kidney disease or acute pancreatitis.
- Low magnesium causes tetany directly and also lowers calcium.
- Alkalosis, for example from hyperventilation, increases calcium binding to albumin and lowers ionized calcium even when total calcium is normal.
- Severe hypocalcemia can cause laryngospasm, seizures and a long QT interval: it is an emergency.
- Simple cramps with negative signs are usually benign nocturnal or exercise cramps, dehydration, low potassium or medicines.
Usefulness and limits
- Chvostek is positive in a small share of healthy people and is often absent in chronic hypocalcemia: it is neither sensitive nor specific.
- Trousseau is more specific than Chvostek, but can also be positive with low magnesium, alkalosis or potassium disorders.
- Confirm with ionized calcium (or total calcium corrected for albumin), magnesium, phosphate, parathyroid hormone and kidney function.
Test yourself
Think of the answer, then tap the question to see it.
Where is the tap given to elicit the Chvostek sign?
Over the facial nerve just in front of the ear, below the zygomatic arch; it is positive if the muscles of the same side of the face twitch.
How is the Trousseau sign elicited?
A blood pressure cuff on the upper arm is inflated above systolic pressure for up to about three minutes; it is positive if carpal spasm appears.
Why can hyperventilation cause tetany?
Respiratory alkalosis increases the binding of calcium to albumin, which lowers ionized calcium.
Which of the two signs is more specific for hypocalcemia?
The Trousseau sign; Chvostek can be positive in healthy people and is often absent in chronic hypocalcemia.
Connections
See it in 3D5
The structures of Durgical's 3D anatomy where it is found.
Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.
Sources: Hypocalcemia (MSD Manual Professional Edition, 2024); Muscle Cramps (MSD Manual Professional Edition, 2024).
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Representative model, for educational purposes only.