<embedvideo service="youtube" Alignment="right">https://www.youtube.com/watch?v=2quH8gvtEAw</embedvideo>Chvostek’s sign is a twitch, spasm or tetanic, cramp-like contraction of some or all of the ipsilateral facial muscles on tapping over the pes anserinus anterior to the tragus. It is classically a sign of tetany but may also occur with hyperreflexia due to upper motor neuron dysfunction.
Various degrees of response may occur (Video). The sign is minimal if only a slight twitch of the upper lip or the angle of the mouth results; moderate if there is movement of the ala nasi and the entire corner of the mouth; maximal if the muscles of the forehead, eyelid, and cheek also contract. When the response is marked, even muscles supplied by the trigeminal nerve may respond. When very active the response may be elicited merely by stroking the skin in front of the ear. Schultz's sign is the same response elicitied by percussing midway between the zygomatic arch and the angle of the mouth.
Chvostek's sign is the result of a hyperexcitability of the motor nerves, in this instance the facial nerve, to mechanical stimulation. Chvostek’s sign is elicited by percussing over the pes anserinus. The motor Tinel’s sign has been reported as evidence of abnormal mechanosensitivity in entrapment neuropathies but may also occur in normals. Both Chvostek’s sign and the Lust peroneal phenomenon are probably examples of a motor Tinel’s sign.
See Kamalanathan for another video, although it is much less dramatic than this one. The Méneret paper shows multiple videos eliciting Chvostek’s sign in normal individuals. YouTube offers multiple examples. Trousseau's sign is more specific than Chvostek's sign for latent tetany.
Video legend. A patient demonstrating her own Chvostek’s sign, due to transient hypocalcemia that developed post-thyroidectomy. She also had a positive Trousseau’s sign. Modified with permission from original video.
[[File:Fig 1 OK sign AIN.jpg|thumb|Figure 1]][[File:Fig 2 OK sign high median neuropathy.jpg|thumb|Figure 2]]The OK (pinch, straight thumb) sign refers to an inability to form the “OK” sign. Patients with weakness of the flexor pollicis longus and the flexor digitorum profundus to the index finger are unable to oppose the tips of the thumb and index finger to form a proper circle, but make a triangle instead, touching the finger pads.(1,2) These muscles are innervated by the anterior interosseous nerve, and the OK sign may be seen in either anterior interosseous or high median neuropathy.References
The median nerve may rarely be entrapped proximally where it passes between the two heads of the pronator teres or by the ligament of Struthers, an anomalous fibrous band running from a distal humeral supracondylar spur to the medial epicondyle. Anterior interosseous neuropathy palsy often occurs as an isolated manifestation of neuralgic amyotrophy.(3) Recent MRI evidence indicates the process in many cases of AIN palsy predominantly involves AIN fascicles in the main trunk of the median nerve in the upper arm.(4)
In this 1. Campbell WW. Clinical signs in neurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016.2. Campbell WW. Barohn RJ. DeJong's the neurologic examination, 8th ed. Philadelphia: Wolters Kluwer, 2020.3. Athappan G, Ariyamuthu VK. Images in clinical medicine. Chvostek's sign and carpopedal spasm. N Engl J Med. 2009;360:e24. 4. Narayan SK, Sivaprasad P, Sahoo RN, et al. Teaching video httpsNeuroImage: Chvostek sign with Fahr syndrome in a patient with hypoparathyroidism. Neurology 2008;71:e79. 5. Kamalanathan S, Balachandran K, Parthan G, et al. Chvostek's sign://wwwa video demonstration.youtubeBMJ Case Rep.com/watch?v=HVHegl-42PE Dr2012;2012. Nabil Ebraheim discusses AIN and the OK 6. Méneret A, Guey S, Degos B. Chvostek sign, frequently found in healthy subjects, is not a useful clinical sign. Neurology. 2013;80:1067.
Figure 1. Patient demonstrating OK sign on the right due to AIN palsy.
Figure <embedvideo service="youtube" Alignment="right"></embedvideo>Myotonia is a disorder of the muscle membrane causing a kind of sustained muscle contraction, an inability to relax. (1, 2) Tone is normal when the muscles are relaxed, but contraction produces a temporary involuntary tonic persistence of muscle contraction with slow relaxation. On Myotonia typically improves with repeated contractions, the rightwarm up phenomenon, and may worsen in the cold or after prolonged rest. Paradoxical myotonia worsens after repetitive contraction. In grip myotonia, the patient with proximal median neuropathyhas difficulty letting go of an object after gripping it strongly. Percussion myotonia is elicited by tapping on the muscle. Eyelid myotonia may cause transient difficulty opening the eyes after a forceful contraction or transient lid retraction after looking up. Myotonia occurs in myotonic dystrophy types 1 and 2, the sodium channelopathies (hyperkalemic periodic paralysis and paramyotonia congenita), which developed chloride channelopathies (myotonia congenita) and other conditions. The various conditions causing myotonia that are not DM1 or DM2 are sometimes referred to as the nondystrophic myotonias. Testing in the patient shown in the video showed a complication following mutation in the SCN4A gene diagnostic of a retrograde brachial angiogramsodium channelopathy, one of the nondystrophic myotonias.(3) Examination showed grip myotonia and prominent delayed relaxation of the eyelids after forced eye closure (eyelid myotonia). Video legend. Patient with eyelid myotonia showing delayed relaxation of the eyelids after forced eye closure. Normal hand on Also note the full beard that the leftpatient cited as helpful for mitigating facial muscle stiffening and pain in cold weather.
==References==
1. Campbell WW. Barohn RJ. DeJong's the neurologic examinationVideo courtesy of Constantine Farmakidis MD and Srijan Adhikari MD, 8th ed. Philadelphia: Wolters Kluwer, 2020University of Kansas Medical Center.
2. Campbell WW. Clinical signs in neurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016.==References==
31. Akane M, Iwatsuki K, Tatebe M, et al Campbell WW. Anterior interosseous nerve and posterior interosseous nerve involvement Clinical signs in neuralgic amyotrophy. Clin Neurol Neurosurgneurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016;151:108-112.
42. Pham Roberts K, Kentris M, Bäumer P, Meinck HM, Schiefer J, et al. Anterior interosseous nerve syndromeMyotonia. 2022 May 8. In: fascicular motor lesions of median nerve trunkStatPearls [Internet]. NeurologyTreasure Island (FL): StatPearls Publishing; 2022 Jan–. 2014;82PMID:598-60632644698.
3. Adhikari S, Statland J, Farmakidis C. Eyelid myotonia and face stiffness in skeletal muscle sodium channelopathy. RRNMF Neuromuscular Journal 2021:2;71-72.
[[Category:Motor Signs]]
