Hemifacial spasm is a nervous system condition in which the muscles on one side of the face twitch. The cause of hemifacial spasm is most often a blood vessel touching or pulsing against a facial nerve. A facial nerve injury or a tumor also can cause it. Sometimes there is no known cause.
Common symptoms of hemifacial spasm include jerking of muscles in the face that are most often:
- On one side of the face.
- Not controllable.
These muscle movements, also called contractions, often start in the eyelid. Then they might move on to the cheek and mouth on the same side of the face. At first, hemifacial spasms come and go. But over months to years, they occur almost all the time.
Sometimes, hemifacial spasms occur on both sides of the face. However, the twitching doesn't occur on both sides of the face at the same time.
A blood vessel touching a facial nerve is the most common cause of hemifacial spasm. A facial nerve injury or a tumor also can cause it. Sometimes the cause isn't known.
Hemifacial spasm sometimes starts as a result of:
- Moving the muscles in the face.
- Being tired.