A positive Chvostek sign is a visible twitch of the facial muscles triggered by tapping on the facial nerve, just in front of the ear. It’s a bedside test used to check for neuromuscular irritability, most commonly associated with low calcium levels in the blood (hypocalcemia). The test takes only a few seconds and requires no equipment beyond a fingertip or small reflex hammer.
How the Test Works
To perform the test, a clinician taps lightly over the facial nerve where it runs along the cheekbone, near the jawline. The two most common spots are just in front of the ear canal along the cheekbone ridge, or on the soft tissue of the cheek about halfway between the earlobe and the corner of the mouth. If the nerve is abnormally excitable, the muscles on that same side of the face will visibly contract.
In a mild positive response, only the muscles around the mouth twitch. In a more pronounced response, the muscles around the eye and the side of the nose also contract. This grading matters clinically because a stronger response generally suggests greater nerve irritability.
Why the Facial Nerve Becomes Excitable
Calcium plays a central role in how nerves fire and muscles contract. When blood calcium drops too low, nerves become easier to trigger. They fire with less stimulation than they normally would, which is why a simple tap on the cheek can set off a visible muscle twitch.
Hypocalcemia is the classic cause, but other electrolyte imbalances can produce the same effect. Low magnesium levels reduce the body’s ability to regulate calcium, compounding the problem. Alkalosis, a shift in blood pH that can happen during rapid breathing or hyperventilation, also lowers the amount of usable calcium in the bloodstream even when total calcium levels appear normal. Any of these conditions can make the facial nerve hyperexcitable enough to produce a positive Chvostek sign.
How Reliable Is the Test?
The Chvostek sign is a useful screening clue, but it has significant limitations. A 2016 study in Neurology: Clinical Practice found its sensitivity for hypocalcemia was only about 26%, meaning it misses roughly three out of four people who actually have low calcium. Its specificity, however, was 96%, meaning a negative result is fairly good at ruling out the condition.
Perhaps more importantly, some people with completely normal calcium levels will test positive. The researchers in that study hypothesized that a positive sign can result from neural and muscular hyperexcitability unrelated to calcium levels. In other words, some people simply have more reactive facial nerves. This is why a positive Chvostek sign alone is never enough to diagnose hypocalcemia. Blood work to directly measure calcium (and often magnesium and other electrolytes) is always the next step.
Chvostek Sign vs. Trousseau Sign
The Trousseau sign is the other classic bedside test for low calcium, and the two are often performed together. For the Trousseau test, a blood pressure cuff is inflated on the upper arm for a few minutes. If the hand and fingers go into a characteristic spasm (the fingers draw together and the wrist flexes), the test is positive.
The Trousseau sign is considerably more accurate. Its sensitivity and specificity for hypocalcemia are reported at 94% and 99%, respectively, making it far more reliable than the Chvostek sign for confirming a diagnosis. Like the Chvostek sign, it can occasionally appear in people with normal calcium, but this happens much less often. When a clinician suspects low calcium, the Trousseau sign offers stronger diagnostic evidence.
What Causes the Low Calcium Behind It
A positive Chvostek sign is not a diagnosis on its own. It’s a physical finding that points toward an underlying problem. The most common reasons for hypocalcemia include underactive parathyroid glands (which regulate calcium), vitamin D deficiency, kidney disease that impairs calcium balance, and certain medications that lower calcium as a side effect. Thyroid or parathyroid surgery is a particularly well-known trigger because the parathyroid glands sit directly behind the thyroid and can be damaged or temporarily stunned during the procedure.
If you’ve had the test performed and it was positive, your doctor will typically order blood tests to check your calcium, magnesium, vitamin D, and parathyroid hormone levels. These results together clarify whether a true electrolyte imbalance exists and point toward the underlying cause. Treatment depends entirely on what’s driving the imbalance, ranging from simple supplementation for mild deficiency to more targeted management for gland or kidney problems.
Symptoms That Often Accompany It
A positive Chvostek sign rarely appears in isolation. If low calcium is the cause, you may also notice tingling or numbness around the mouth, in the fingertips, or in the toes. Muscle cramps, especially in the hands and feet, are common. In more severe cases, people experience muscle spasms, difficulty breathing from throat tightness, or even seizures. These symptoms reflect the same underlying nerve hyperexcitability that the Chvostek test detects, just showing up in different parts of the body.