Chvostek Sign · What Is It, What Does It Indicate, and More

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, just in front of the ear. The Chvostek sign elicits an atypical reaction of the facial nerve, or seventh cranial nerve (CN VII), 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 nerves’ threshold potential, which is the critical point before the nerve activates. Hypocalcemia decreases the threshold needed for the nerve 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. 

A positive Chvostek sign raises suspicion for low calcium levels. Maintaining stable calcium levels is necessary for regulating the function of many cellular processes, including nerve activity, muscular contraction, hormone secretion, and blood coagulation.   

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 syndrome, that involve the parathyroid glands.   

Aside from hypocalcemia, other factors can cause a positive Chvostek sign, including kidney failure, acute pancreatitis, and certain medications such as bisphosphonates and proton pump inhibitors. Electrolyte imbalances, such as low levels of vitamin D or magnesium, can also increase the excitability of nerves and lead to a positive Chvostek sign. Additionally, this sign may present in respiratory alkalosis, most commonly caused by hyperventilation.  

The reliability of the Chvostek sign is questionable. According to more recent studies, it can frequently be found in healthy individuals or even in individuals with increased calcium levels rather than decreased. Therefore, if a positive Chvostek sign occurs, it’s important to investigate all possible causes of the sign.