Hemifacial spasm is a neuromuscular disorder characterized by frequent involuntary contractions of the muscles on one side of the face. The disorder occurs in both men and women, although it more frequently affects middle-aged or elderly women. The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye. The spasm may then gradually spread to involve the muscles of the lower face, which may cause the mouth to be pulled to one side. Eventually the spasms involve all of the muscles on one side of the face almost continuously. The condition may be caused by a facial nerve injury or a tumor, or it may have no apparent cause. Very commonly, hemifacial spasm is caused by a blood vessel pressing on the facial nerve.

Treatment of hemifacial spasm frequently consists of injecting botulinum toxin (commonly called Botox) into the affected muscles. Surgery may be used for some cases.

Untreated cases of hemifacial spasm generally do not have dire consequences. Prognosis for treated cases varies from patient to patient.

Prepared by the National Institutes of Health