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What is hemifacial spasm?

Hemifacial spasm (HFS) is a condition that affects half of your face, causing involuntary contraction of the facial muscles. It usually starts with a twitching around one eye and then progresses to gradually involve your mouth, causing your eye to close and the corner of your mouth to become pulled up. Some people also hear a clicking sound on the side that is affected when the spasm comes. Gradually the spasms become worse and may become permanent. Although it is not life-threatening, it can affect quality of life.

What causes it?

The facial nerve carries signals from the brain to make your facial muscles contract or relax. There is a facial nerve for each side of the face. It starts deep inside the brain and makes its way past many structures to reach the face. The most common cause of hemifacial spasm is compression of the facial nerve by an artery in the brain. The compression causes the nerve to misfire making your facial muscles contract when you don’t want them to.

There are other rarer causes of hemifacial spasm such as infections, strokes or tumours. Sometimes there is no obvious cause and doctors may then call it idiopathic hemifacial spasm. Because the causes of hemifacial spasm are not inherited, it is unlikely that you will pass the condition on to your children.

How common is it?

Hemifacial spasm is a rare condition, affecting 8 in every 100,000 people. It affects men and women, although women tend to be affected slightly more often than men. Symptoms usually start in middle age.

How do doctors diagnose it?

If you are worried about twitching on one side of your face, you should see your GP. If they think you may have hemifacial spasm, they will refer you to a specialist (ophthalmologist or neurologist). Usually, the specialist will organise for you to have an MRI scan of the brain to confirm the diagnosis.

Treatments for hemifacial spasm

Hemifacial spasm is unlikely to improve without treatment. Although there is no guaranteed cure, several treatments are available.

  • Muscle relaxant (toxin) injections – when injected, the toxin disrupts nerve messages to muscles and causes paralysis, stopping the spasms. Generally, multiple injections are given both above and below the eye, and in the cheek. It takes between one and four days for the paralysis to begin. The complete effect usually takes about a week. The treatment often lasts up to four months. Muscle relaxant injections work for about 70-80% of people with hemifacial spasm, and is currently the most commonly used treatment. Common but temporary side effects include dry eyes, drooping eyelids (ptosis), and facial weakness. Rarely, double vision can occur, but fortunately, this is temporary. Short-term blurry vision can occur due to drying of the eye surface, but this is easily treated with artificial tears.
  • Medications - can be helpful when the spasms are mild or infrequent. Anti-epileptic medicines such as carbamazepine and topiramate can be helpful in some people with hemifacial spasm. These medicines work by quieting nerve impulses. Benzodiazepine such as diazepam and clonazepam are sedatives. They can relax muscle spasms but may also make you feel sleepy. The response to these medicines can vary and it may take time to get the right dose. They will need to be taken on a long-term basis.
  • Surgery - Microvascular decompression can relieve the compression caused by the blood vessel on the facial nerve. Surgery can be curative but there are some serious side-effects that may occur as a result of surgery. For this reason, surgery is usually reserved for cases where the spasms are severe and disabling when other treatments have failed.
  • Muscle-Relaxant injections are available at Eye Specialist Institute for the treatment of blepharospasm, hemifacial spasm, and strabismus.