Chvostek sign
TheChvostek sign(/ˈkvɒstɪk/) is aclinical signthat someone may have a low blood calcium level (a decreased serum calcium, calledhypocalcemia). The Chvostek sign is the abnormal twitching of muscles that are activated (innervated) by thefacial nerve(also known as Cranial Nerve Seven, or CNVII).[1]When the facial nerve istappedin front of the ear, the facial muscles on the same side of the face will contract sporadically (called ipsilateral facial spasm). The muscles that control the nose, lips and eyebrows are often the ones that will spasm.
These facial spasms are caused by the nerves that control the muscle being easily excited (called hyperexcitability) due to hypocalcemia. Hypocalcemia can be caused by many things, including parathyroid conditions (such as when theparathyroid glanddoes not function well, calledhypoparathyroidism) and vitamin diseases (such as avitamin D deficiency). Sometimes, the Chvostek sign can be caused by other conditions which interfere with the balance of calcium, such as imbalanced acid and alkaline in blood causingrespiratory alkalosis(an alkaline blood pH).
TheTrousseau sign of latent tetanyis another sign of decreased calcium in blood where muscles in the hand contract when thebrachial arterysupplying the area is occluded. The Trousseau sign of latent tetany also generally occurs earlier than the Chvostek sign and is a more accurate predictor of hypocalcemia, allowing clinicians to recognise the condition earlier.
Etymology[edit]
The sign is named afterFrantišek Chvostek,an Austrian-born surgeon who lived in Moravia, in the Czech Republic. In his professional life, Chvostek devoted himself to the study of etiopathogenesis and to the treatment of neurological disorders, including by means of electrotherapy. In 1876, he first described the sign that bears his name.[2]Later it was independently described by another Austrian physician,Nathan Weiss(1851–1883), in 1883.[3]
Features[edit]
Chvostek sign – type I[edit]
It is obtained by striking with a finger or a hammer a point that is approximately 2 cm in front of the lobe of the ear and about 1 cm below thezygomatic process.Response occurs in the form of ipsilateral contraction of some or all of the muscles innervated by the facial nerve.[4]The effect is the lateral deviation of the labial and nasal fold toward the stimulated side.
Chvostek sign – type II[edit]
Hitting a point between the middle third and upper third of the line joining the angle of the mouth to the zygomatic process gives rise to only a contraction of the muscles of the mouth and nose.
Causes[edit]
Chvostek's sign is found intetany.However, it may also be present inhypomagnesemia.[5][6]Magnesium is a cofactor foradenylate cyclase,which catalyzes the conversion of ATP to 3',5'-cyclic AMP. The 3',5'-cyclic AMP (cAMP) is required forparathyroid hormoneactivation.[7]It is frequently seen in alcoholics, persons with diarrhea, patients takingaminoglycosidesor diuretics, because hypomagnesemia can cause hypocalcemia. It is also seen in measles, tetanus andmyxedema.
It can also be found in subjects with respiratory alkalosis, for example as a result of hyperventilation syndrome, which can lead to a drastic reduction of the concentration in serum of calcium ions while at normal levels, for the binding of a significant proportion of ionized calcium (Ca2+) with albumin and globulins.
Clinical significance[edit]
Chvostek's sign is not a veryspecificsign of tetany as it may be seen in 10% to 25% of healthy adults.[8]It is therefore not a reliable clinical sign for diagnosing latenttetany.[9][10]The sensitivity is lower than that in the corresponding Trousseau sign as it is negative in 30% of patients with hypocalcemia.[11]Due to the combination of poor sensitivity and specificity the clinical utility of this sign is reduced.[8]
References[edit]
- ^Jesus, JE; Landry, A (Sep 13, 2012). "Images in clinical medicine. Chvostek's and Trousseau's signs".The New England Journal of Medicine.367(11): e15.doi:10.1056/NEJMicm1110569.PMID22970971.
- ^Chvostek F.Beitrag zur Tetanie.Wien Med Press 1876;17:1201-3, 1225–27, 1253–58, 1313–16.
- ^Weiss N. Centralbl Gesammt Ther 1883;1:9.
- ^Krogh, L; Wynne, JM; Cywes, S (Aug 17, 1968). "The value of Chvostek's sign in tetany".South African Medical.42(32): 846–7.PMID5680230.
- ^Weisinger, JR; Bellorín-Font, E (Aug 1, 1998). "Magnesium and phosphorus".Lancet.352(9125): 391–6.doi:10.1016/S0140-6736(97)10535-9.PMID9717944.
- ^Flink, EB (1981). "Magnesium deficiency. Etiology and clinical spectrum".Acta Medica Scandinavica. Supplementum.647:125–37.PMID7020347.
- ^Goljan, EF. Rapid Review Pathology. Mosby, Elsevier, 2007; pp. 504.
- ^abMéneret, A; Guey, S; Degos, B (Mar 12, 2013)."Chvostek sign, frequently found in healthy subjects, is not a useful clinical sign".Neurology.80(11): 1067.doi:10.1212/WNL.0b013e31828728bc.PMID23479466.
- ^Hoffman, E (Jul 1958). "The Chvostek sign; a clinical study".American Journal of Surgery.96(1): 33–7.doi:10.1016/0002-9610(58)90868-7.PMID13545482.
- ^Garrad, P; Perks, AM (Aug 1990). "The effects of temperature change on lung liquid production by in vitro lungs from fetal guinea pigs".Journal of Developmental Physiology.14(2): 109–14.PMID2092052.
- ^Fonseca, OA; Calverley, JR (Aug 1967). "Neurological manifestations of hypoparathyroidism".Archives of Internal Medicine.120(2): 202–6.doi:10.1001/archinte.1967.00300020074009.PMID4952674.