Overview of Hemifacial Spasm
Hemifacial spasm is a neuromuscular disorder characterized by frequent, involuntary muscle contractions (tics or spasms) in the face. It usually affects only one side of the face, but in severe cases, tics may occur on both sides.
The early symptom is usually an intermittent tic of the eyelid muscle, which may eventually lead to complete closure of the eye. The spasm may then spread and eventually involve all of the muscles in the affected side of the face.
Incidence and Prevalence of Hemifacial Spasm
Hemifacial spasm usually occurs in middle-aged and older people and is more common in women. It is rare, affecting 8 out of 100,000 men and 15 out of 100,000 women in the United States. Left-sided spasm is slightly more common than right- sided spasm.
Being middle-aged or older is a risk factor for hemifacial spasm. If a person younger than 40 is affected, there may be an underlying neurological disease (e.g., multiple sclerosis).
Hemifacial spasm may be caused by an injury to the seventh cranial, or facial, nerve; a tumor or a blood vessel pressing on the nerve; or Bell's palsy. The cause may also be unknown. One of the most common triggers is a blood vessel pressing against the facial nerve, which causes the surrounding muscles to twitch or spasm.
The symptom is facial muscle spasm that usually begins in the eyelid and around the eye. The spasm varies in intensity and in how much of the face it affects.
A complete neurological exam is performed and if the physician suspects hemifacial spasm, an electromyogram is ordered. Most cases of hemifacial spasm are caused by a blood vessel pressing on the facial nerve, and this vessel is usually too small to be detected by magnetic resonance imaging (MRI), computed tomography (CAT scan), or angiography. These imaging tests are usually ordered when a lesion or tumor is suspected.
An electromyogram is used to diagnose muscle problems caused by nerve dysfunction. The procedure is performed on an outpatient basis and takes about 2 hours. A small needle is inserted into each muscle being examined. The needle is attached to a wire and connected to a device that records electrical activity produced when the patient contracts and releases each muscle.