Hemifacial spasm is a type of movement disorder that occurs when the facial nerve is compressed or irritated. It is characterized by very rapid, abnormal contractions of the muscles on one side of the face. Hemifacial spasm may be caused by a facial nerve injury, a tumor, or it may have no apparent cause. If there is no apparent cause, doctors may call the condition idiopathic of unknown cause hemifacial spasm. The most common cause of hemifacial spasm is a blood vessel pressing on the facial nerve at the place where it exits the brainstem.
Muscle twitch: Causes, symptoms, treatment, and prevention
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. They also tend to occur more often on the left side of your face.