A muscle spasm — also known as a charley horse, muscle cramp or twitch — is a sudden, involuntary movement in one or more muscles. Common causes include stress, exercise, or dehydration, but nerve ...

‌Hemifacial spasm is a disorder of the nerves and muscles that causes nonpainful involuntary twitching on one side of the face. Many people refer to hemifacial spasms as lip muscle spasms. Hemifacial ...

Stiff person syndrome (SPS) causes you to have muscle stiffness and spasms, often triggered by sudden noises or touch. You can use medications like muscle relaxants and anticonvulsants to relieve ...