What Is It, What Does It Indicate, and More
Author: Nikol Natalia Armata
Editors: Alyssa Haag, Józia McGowan, DO
Illustrator: Jillian Dunbar
Copyeditor: Joy Mapes
What is the Chvostek sign?
The Chvostek sign is a clinical finding associated with hypocalcemia, or low levels of calcium in the blood. This clinical sign refers to a twitch of the facial muscles that occurs when gently tapping an individual's cheek, in front of the ear. The Chvostek sign aims to elicit an atypical reaction of the facial nerve, the nerve that innervates many of the muscles of the face. The pressure caused by the tapping acts as a triggering stimulus for involuntary contractions of the facial muscles ipsilaterally, or on the side that the clinical sign is performed. The sign is considered negative when no contractions of the facial muscles occur after stimulation of the facial nerve.
Ionized calcium, or Ca+2, is responsible for controlling the neuron’s threshold potential, which is the critical point before the neuron activates. Hypocalcemia, or an atypically low level of calcium in an individual’s blood, decreases the threshold needed for the neuron to transmit a signal to the muscle. Therefore, low calcium levels result in hyperexcitability of the nerves, which can result in spontaneous twitches, as seen with a positive Chvostek sign.
How do you pronounce “Chvostek sign”?
The word “Chvostek” is pronounced as: vos-tek. Therefore, “Chvostek sign” is pronounced: vos-tek sain.
How is the Chvostek sign performed?
The Chvostek sign is performed by gently tapping the individual’s cheek 2 centimeters (about 0.75 inch) in front of the ear, over the route of the facial nerve, also known as the seventh cranial nerve (CN VII). Twitching of the mouth and periorbital muscles, or muscles around the eyes, on the same side as the stimulated facial nerve is considered a positive Chvostek sign.
What does a positive Chvostek sign indicate?
A positive Chvostek sign mainly indicates that the individual’s calcium levels are low. Maintaining stable calcium levels is necessary for regulating the function of many cellular processes, including neuronal activity, muscular contraction, hormone secretion, and blood coagulation (i.e., process of blood clot formation).
Parathyroid hormone (PTH), a hormone released by the parathyroid glands, regulates calcium levels in the body. When the calcium level is too low, PTH is released into circulation. Hypocalcemia usually results from a condition known as hypoparathyroidism, which is due to inadequate production of PTH. Hypoparathyroidism can occur because the parathyroid glands have been surgically removed or due to surgical removal of the thyroid gland, which can indirectly damage the blood supply to the parathyroid glands. Less frequently, hypoparathyroidism is the result of autoimmune disorders, such as autoimmune polyendocrine syndrome type 1), or genetic conditions, like DiGeorge’s syndrome, that involve the parathyroid glands.
Aside from hypocalcemia, other factors can be responsible for a positive Chvostek sign, including kidney failure, acute pancreatitis, and certain medications (e.g., bisphosphonates, proton pump inhibitors). Electrolyte imbalances, such as low levels of vitamin D and magnesium, can also increase the excitability of the facial nerves and indicate a positive Chvostek sign. Additionally, this sign may present in respiratory alkalosis, most commonly caused by hyperventilation, or fast breathing.According to a 2013 study by Méneret, Guey, and Degos, the reliability of the Chvostek sign is questionable, as it is frequently found in healthy individuals. The results of their study revealed that 25% of healthy subjects had a positive Chvostek sign, whereas 29% of individuals with hypocalcemia had a negative Chvostek sign.
What does a negative Chvostek sign indicate?
A negative Chvostek sign cannot exclude hypocalcemia as a possible diagnosis in an individual. While the Chvostek sign frequently suggests hypocalcemia, it is not a reliable sign for diagnosis, so absence of the sign is not conclusive.
What are the most important facts to know about the Chvostek sign?
The Chvostek sign is a clinical finding usually associated with hypocalcemia, or atypically low levels of calcium in the blood. This clinical sign presents after gently tapping over the cheek, 2 cm in front of the ear. If the Chvostek sign is positive, ipsilateral twitching of the facial muscles occurs, whereas there is no movement when the sign is negative. A positive Chvostek sign may indicate hypocalcemia or other electrolyte imbalances, as well as severe conditions, like kidney failure or acute pancreatitis. On the other hand, a negative Chvostek sign does not necessarily exclude hypocalcemia.
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Resources for research and reference
Dulak, D., & Naqvi, I. (2020, November 29). Neuroanatomy, cranial nerve 7 (facial). In StatPearls [Internet]. Retrieved June 11, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK526119/
Méneret, A., Guey, S., & Degos, B. (2013). Chvostek sign, frequently found in healthy subjects, is not a useful clinical sign. Neurology, 80(11): 1067. DOI: 10.1212/wnl.0b013e31828728bc
Merriam-Webster. (n.d.). Chvostek's sign. In Merriam-Webster.com medical dictionary. Retrieved March 27, 2021, from https://www.merriam-webster.com/medical/Chvostek%27s%20sign
National Organization for Rare Disorders (NORD), & Shoback, D. (2017). Hypoparathyroidism. In Rare disease database. Retrieved March 28, 2021, from https://rarediseases.org/rare-diseases/hypoparathyroidism/