Hemifacial spasms happen when the muscles on only one side of your face twitch without warning. These types of spasms are caused by damage or irritation to the facial nerve, which is also known as the seventh cranial nerve. Facial spasms occur when the muscles contract involuntarily because of this nerve irritation.

Hemifacial spasms are also known as tic convulsif. At first, they may appear only as small, barely noticeable tics around your eyelid, cheek, or mouth. Over time, the tics may expand to other parts of your face.

Hemifacial spasms can happen to men or women, but they’re most common in women over 40. They also tend to occur more often on the left side of your face. 

Hemifacial spasms aren’t dangerous on their own. But a constant twitch in your face can be frustrating or uncomfortable. In severe cases, these spasms can limit function due to involuntary eye closing or the impact they have on speaking.

In some cases, these spasms may indicate that you have an underlying condition or an abnormality in your facial structure. Either of these causes can compress or damage your nerves and make your face muscles twitch.