myotonia
noun
myo·to·nia ˌmī-ə-ˈtō-nē-ə 
: tonic spasm of one or more muscles
also : a condition characterized by such spasms
myotonic
ˌmī-ə-ˈtä-nik
adjective 
Example Sentences
Recent Examples on the Web Because myotonia congenita is a recessive gene, goats that are crossbred with other breeds typically do not display fainting behaviors. 
Sarah Gibbens, National Geographic, 16 Feb. 2017
Sarah Gibbens, National Geographic, 16 Feb. 2017 Word History
Etymology
New Latin
First Known Use
1886, in the meaning defined above
Medical Definition
myotonia
noun
myo·to·nia ˌmī-ə-ˈtō-nē-ə
: tonic spasm of one or more muscles
also : a condition characterized by such spasms