THE INCREASED mechanical irritability of the peripheral nerves in tetany was described by Chvostek1 in 1876 and 1879. Only the excessive irritability of the facial nerve, however, was named after him. He recommended percussing the facial nerve in front of the external auditory meatus and claimed that the muscular contraction evoked was not a reflex, but was due to "direct stimulation of the facial nerve."
Schultze2 observed that Chvostek's sign could also be easily evoked by percussion of an area between the corner of the mouth and the zygomatic arch. The responses to this mode of stimulation are now often called Chvostek signs II and III, according to the extensiveness of the response within the muscles supplied by the middle facial branch. The Chvostek sign is often present in this form only. In some cases of tetany Schultze observed, moreover, that with percussion of the middle branch muscles
KUGELBERG E. THE MECHANISM OF CHVOSTEK'S SIGN. AMA Arch NeurPsych. 1951;65(4):511-517. doi:10.1001/archneurpsyc.1951.02320040101010