Hemifacial Spasm

What is hemifacial spasm?

Hemifacial spasm is a rare neurological condition that causes involuntary muscle twitching on one side of your face. It usually starts around one eye and gradually spreads, tending to get worse over time.

What are the symptoms of hemifacial spasm?

The first sign is usually intermittent twitching of one eyelid, which comes and goes. Over months or years, this can progress to:

• your eye closing involuntarily, sometimes forcefully
• your eyebrow lifting at the same time as your eye twitches
• spasms in your lower face, which may pull your mouth to one side
• spasms affecting all the muscles on one side of your face, which can become almost constant.

The twitching is usually painless, but it can be tiring and may knock your confidence. Stress, fatigue, eating and anxiety tend to make it worse, and unlike many other movement conditions, the spasms can continue while you're asleep, sometimes leading to sleep problems.

Hemifacial spasm almost always affects only one side, more often the left, though rarely both sides can be involved. Some people also notice a clicking sound in the ear, ear pain, or changes to their hearing.

What are the causes of hemifacial spasm and who is at risk?

In most cases, a blood vessel, usually a small artery, presses against the facial nerve close to where it leaves the brainstem. This constant contact irritates the nerve and disrupts its normal signalling, so it fires unpredictably and causes muscle twitching.

Other, less common causes of the same kind of nerve irritation include:

• an injury near the facial nerve, or a severe episode of Bell's palsy
• damage to the brainstem, for example from multiple sclerosis or a stroke
• a tumour, cyst or blood vessel abnormality pressing on the nerve
• ear problems, such as infections or cholesteatoma (a growth of skin cells in the middle ear)
• a tumour of the parotid gland (a saliva gland near the ear).

Hemifacial spasm is rare, affecting roughly 11 people in every 100,000, and women are around twice as likely to develop it as men. It usually begins in adulthood, most often between your 40s and 60s. Around 4 in 10 people with hemifacial spasm also have high blood pressure, so it's worth having yours checked.

Are there different types of hemifacial spasm?

Hemifacial spasm is classified into two types, based on how it develops:

• Primary hemifacial spasm: This is caused directly by a blood vessel pressing on the facial nerve. It's the most common type, and spasms may take months or years to spread from the eye to the lower face
• Secondary hemifacial spasm: This is caused by an underlying condition irritating the nerve, such as previous injury, Bell's palsy, or a structural problem. The upper and lower face are more likely to be affected together, and symptoms come and go before becoming more frequent.

It's easy to confuse hemifacial spasm with other facial movement conditions, so getting the right diagnosis matters. In particular, it's not the same as blepharospasm, which causes twitching around both eyes rather than one side of the face.

How is hemifacial spasm diagnosed?

Diagnosis is mainly based on a detailed history and a physical and neurological examination, looking at the pattern, frequency and spread of your twitching. Because hemifacial spasm is rare, it's sometimes mistaken for other conditions, such as Bell's palsy or trigeminal neuralgia, so it's best assessed by a specialist.

You'll usually also be offered:

• an MRI scan of the brain, with detailed views of the area where the facial nerve leaves the brainstem, to rule out tumours or other structural causes and often to identify the blood vessel involved
• an MRA scan (a type of scan that looks at blood vessels) if surgery is being considered, to help plan the operation.

If the type of movement isn't clear from examination alone, a nerve and muscle test called electromyography (EMG) can help confirm the diagnosis.

In severe, longstanding cases, spasms can progress to sustained muscle tightening, forcing the eye shut for periods of time. Because this affects vision in that eye, it can be a safety risk, for example when driving or walking on uneven ground, which is one of the reasons an early diagnosis matters.

How is hemifacial spasm treated?

Non-surgical treatments

Injections to weaken the overactive muscles are usually the first treatment offered, because they work well and have few serious side effects.

You'll usually notice an improvement 3 to 6 days after treatment, with the effect lasting around 3 to 4 months before it wears off, so ongoing injections every few months are needed to keep symptoms controlled.

Possible side effects include eye irritation, eyelid drooping, double vision and temporary facial weakness, which usually settle within 2 to 3 months.

Oral medicines, such as anticonvulsants, muscle relaxants or benzodiazepines, are another option, particularly for people who'd rather avoid injections or aren't suitable for surgery. They don't work for everyone, and side effects such as drowsiness and fatigue are common, especially with long-term use.

Surgical treatment

Surgery, called microvascular decompression, is the only treatment that can permanently cure hemifacial spasm, because it treats the underlying cause rather than just easing symptoms. It's generally only recommended for more severe cases or if muscle-relaxing injections aren’t giving enough relief.

The operation is carried out through a small opening in the skull behind the ear. The surgeon locates the blood vessel pressing on the facial nerve and places a small cushioning pad between the two, relieving the pressure. Many patients notice their spasms ease almost immediately, though for some the improvement happens more gradually.

Most people spend one or two nights in hospital. As with any operation, there are risks, which can include:

• infection
• partial or, rarely, permanent hearing loss on the operated side
• temporary facial numbness or weakness, which usually improves with time
• difficulty speaking or swallowing
• in very rare cases, stroke or bleeding.

When should I see a doctor?

See a doctor if you notice persistent or worsening twitching on one side of your face, particularly if:

• it's spreading from your eye to other parts of your face
• it's starting to interfere with your vision, speech or daily activities
• you also develop facial weakness, numbness, or other new symptoms
• the twitching continues during sleep or is becoming more frequent.

If you're already having injections or taking medicine for hemifacial spasm, keep your follow-up appointments so your treatment can be adjusted if needed, and contact your doctor if side effects appear or your symptoms get worse.