The Chvostek sign is a muscle contraction around the eye caused by gently tapping the side of the face just in front of the ear. Medical professionals often use this sign as a signifier of low blood calcium levels, called hypocalcemia. Checking for the Chvostek sign cannot be used as the only indicator of a this condition, however, because around 25 percent of those displaying this muscle contraction do not have a low blood calcium level.
Patients can have the Chvostek sign induced by a medical professional tapping the nerve in front of the ear with a finger. When this facial nerve is tapped in patients with hypocalcemia, the muscles around the eye on that side of the face contract to induce a winking motion of the eye. The level of contraction of the muscles can be an indicator of the level of calcium in the blood. If there are extremely low levels of calcium in the blood, for example, the muscles around the eye will contract more significantly than in patients with higher levels of calcium.
The Chvostek sign is one of the earliest symptoms of hypocalcemia, and can be seen before the majority of other symptoms can be identified. As hypocalcaemia progresses, and blood calcium drops to dangerously low levels, the muscles of the face and the rest of the body lose elasticity; once the muscles contract because of low calcium in the blood, the Chvostek sign cannot be induced. Other symptoms of hypocalcaemia include abdominal cramps, mood changes, and general weakness.
Older people displaying Chvostek sign can have the symptoms of hypocalcaemia induced by a variety of causes. Alterations made in the types of medications or dosage levels can result in muscle spasms following the tapping of the facial nerve in front of the ear. People placed in stressful situations and those completing large amounts of strenuous, physical exercise can also display symptoms of hypocalcaemia.
Although the contraction of the muscles around the eye is classed as a symptom of blood calcium problems, it can be a reflex occurring naturally in a small number of people. Some infants and elderly people who do not have low blood calcium levels can also show this sign because of damage caused to the contralateral frontal cortex. In such cases, the damaged region of the brain does not pass electrical communications effectively between the central nervous system, brain, and the region of the face displaying the Chvostek sign.