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
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.
Signs and Symptoms
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.
There are three treatments for hemifacial spasm: medication, surgery, and botulinum toxin injections. In most cases, the treatment of choice is botulinum toxin injections, also known as BOTOX® Cosmetic or BTX.
BTX is produced by the Clostridium botulinum bacterium. It is the same toxin that produces botulism (i.e., food poisoning). When injected into the eyelid in minute amounts, BTX is effective in stopping spasms for several months. Because the effects are temporary, the treatment must be repeated periodically. Side effects include drooping eyelids, double vision, and dry eyes. These side effects lessen in time. More about botulinum toxin injections.
Medication is used in mild cases and in patients who refuse BTX or surgery. Benzodiazepines (anxyolytic used as muscle relaxant) and carbamazepine (Tegretol®; antiseizure drug) can help control muscle spasms but are usually less successful than BTX.
These medications produce side effects in the central nervous system, including:
Long-term use of benzodiazepines can lead to dependence. When used with other depressants (e.g., alcohol), there is a great risk for severe respiratory and cardiovascular depression. Drug interactions also can be severe, so the physician should be informed of all prescription and over-the-counter drugs being taken.
Carbamazepine can cause potentially serious adverse effects and the patient is monitored for low white blood cell or platelet counts, signs of bone marrow depression, and liver damage. Patients with high intraocular pressure (IOP) also are monitored because carbamazepine can increase pressure.
Surgery is indicated for severe symptoms caused by blood vessel compression that does not respond to other therapies. In th Janetta procedure, also called microvascular decompression, the blood vessel that is pressing on the facial nerve is repositioned to relieve pressure. This treatment is usually successful and most patients do not require further treatment.
Microvascular decompression is performed by a neurosurgeon in a hospital under general anesthesia and carries associated risks. Some patients have a residual spasm, particularly around the eye, that takes days to months to resolve.
There is no way to prevent hemifacial spasm.