Hemifacial spasm is usually not painful and not considered a health hazard. In advanced cases, however, the eyes may remain squeezed shut for long enough to become dangerous when driving, for example.
Both men and women can develop these facial twitches, but women, especially middle-aged and older women, develop hemifacial spasm at about twice the rate of men. The condition is also somewhat more common in Asian people.
It is a rare condition, seen in approximately 11 out of 100,000 people.
Hemifacial spasm causes the muscles on one side of the face to contract.
Hemifacial spasm is different from other nerve and muscle conditions affecting the face because it tends to affect only one side of the face.
However, there are differences between what is considered typical for hemifacial spasm and other forms of the condition.
A study of 215 people being examined for hemifacial spasm found that:
- 62 percent were most likely caused by a vein putting pressure on the facial nerve
- 18 percent had tics that mimicked hemifacial spasm but were not actually examples of the disease
- 11 percent were due to Bell's Palsy
- 6 percent were the result of injuries to the facial nerve
- 2 percent were linked to hereditary causes
Fewer than 1 percent of cases were caused by direct damage to nerves or the brain's circulatory system
The first sign of hemifacial spasm is usually a twitching in the muscles of the left eyelid. These spasms can be strong enough to pull the eye closed and cause tears to form.
If left untreated, the symptoms of hemifacial spasm can become more severe and affect more and more facial muscles. Twitches can affect the muscles of the mouth and pull it to one side.
Over time, all the muscles on one side of the face can be pulled into a permanent frown. Some individuals may develop spasms on both sides of the face.
Ear pain, a "clicking" in the ear, and changes in hearing can also be symptoms of this condition. Hearing loss also sometimes occurs.
Around 13 percent of people taking part in one study reported a loss of hearing. However, this hearing loss did not appear to relate to how serious their hemifacial spasm symptoms were.
Symptoms of hemifacial spasm usually develop when people are between 40 and 50 years of age.
Hemifacial spasm is caused by irritation to the seventh cranial nerve. This nerve is known as the facial nerve and controls the muscles of the face. It also transmits information about the sense of taste from the tongue and sensations in the ear.
The most frequent source of irritation is a small artery pressing on the facial nerve near the brain stem. Other potential causes include:
- a benign tumor or lesion pressing on the nerve
- abnormal clusters of blood vessels at birth
- nerve injury
Hereditary cases of hemifacial spasm have been identified, although they are not common.
In some cases, hemifacial spasm is the first symptom of multiple sclerosis or MS. When people have MS, their immune system attacks the central nervous system, which results in a wide variety of symptoms.
However, this is extremely rare, with scientific studies showing only 1 to 6 occasions out of several hundred cases in which MS was identified as the cause of a hemifacial spasm.
Although it is rare, doctors still need to check for MS as a possible cause when people under age 40 have a hemifacial spasm.
MRI and CT scans can be used to diagnose the cause of facial spasms.
Facial tics are the key sign of hemifacial spasm. Doctors will observe the person and take a medical history, noting how severe the twitches are and how long the person has had them.
The doctor will then use medical imaging tests to find out what is irritating the facial nerve and rule out the possibility of tumors or brain lesions being the cause. These tests may include:
If imaging tests do not find tumors or lesions, doctors will likely assume that pressure from a blood vessel is causing the hemifacial spasm. These tests cannot always locate the blood vessel that is irritating the facial nerve, however, because the blood vessels are so small.
A hemifacial spasm can be confused with other movement disorders that affect the face. These include facial nerve tics and eyelid spasms. These two conditions affect different areas of the face, and not just one side, which helps doctors accurately diagnose this condition.
To date, researchers have not discovered any ways of preventing hemifacial spasms.
As the spasms are involuntary, the only way to prevent the onset of muscle twitches once the condition develops is through treatment.
The two main ways to treat hemifacial spasm are through injections or surgery.
Botulinum toxin (Botox) shots are used to paralyze the facial muscles and stop the twitching.
These treatments are helpful for 85 to 95 percent of people. The effects wear off after 3 to 6 months so users will need follow-up treatment on a regular basis.
Botox shots may improve facial twitches for up to 6 months.
Although surgery is more involved and invasive, it also provides more permanent and immediate relief.
In a procedure known as microvascular decompression, a surgeon moves the irritating artery away from the facial nerve and places a pad on the nerve to protect it from future compression.
This surgery is reported to be effective 85 percent of the time. It is considered especially helpful for young people and those in the early stages of this condition.
This procedure does have some risk, with one study finding a 1.5 to 8 percent risk of hearing impairment due to this surgery.
Treatment with medication alone has not been found to be effective for this condition.
Stress caused by this condition's uncontrollable twitches is one of the most important side effects of hemifacial spasm. However, as people can relieve their symptoms with injections or surgery, the outlook can be good.
It is important for people to seek treatment and take an active role in their care. Their condition is likely to get worse if it is left untreated, so they should be aware of all the treatment options available.
One study found that close to 50 percent of people treated by one team had to learn about the surgical option for hemifacial spasm through their own efforts.