What is it?
The facial nerve works the muscles of expression. In hemifacial spasm the signals from this nerve escape your control and the muscles on one side of the face contract by themselves. The contractions are short twitches at first, and over time can progress as far as the eyelid staying closed for long spells.
The differences from an ordinary eyelid twitch are clear. Hemifacial spasm is one-sided, carries on for months, spreads to neighbouring muscles, can continue during sleep and increases with excitement and tiredness. A twitch caused by tiredness, on the other hand, can be seen in both eyes and is expected to settle by itself within a few days to a few weeks.
There is a practical reason why this page sits in a dental clinic: people take the twitching for a jaw problem and come to the dentist. In fact the contraction is in the muscles of expression, not in the chewing muscles. If the distinction is not made, years can pass with night guards and trials of muscle relaxants, when this condition is the business of another speciality.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
Contact from a blood vessel next to the nerve
The cause shown most often is a blood vessel resting against the facial nerve where it leaves the brainstem. Over the years the insulation of the nerve weakens and signals are carried without control.
- 02
Structural causes along the path of the nerve
A growth or a blood vessel abnormality along the course of the nerve can produce the same picture, although this is rarer. Ruling out these possibilities is why imaging is requested.
- 03
The period after a previous facial palsy
As a facial palsy heals, the nerve fibres can miss their targets. The result is accompanying involuntary movements, such as the corner of the mouth pulling as the eye closes.
- 04
Harmless conditions it is confused with
Eyelid twitching that comes with lack of sleep, caffeine and stress, tics, and contraction of both eyelids are different pictures. Their course and their treatment are separate from hemifacial spasm.
How does it progress?
- 1
Limited to the eyelid
It begins with short, irregular twitches in the lower or upper eyelid. Symptoms are usually mild at this stage and are taken for a tiredness twitch.
- 2
Spreading to the cheek and the corner of the mouth
The contraction moves on to the cheek and the muscles around the mouth on the same side. The corner of the mouth pulling as the eye closes is the typical look of this stage.
- 3
Established spasm
The contractions get longer and more frequent. Because the eye can stay closed for long spells, reading, looking at a screen and driving can become difficult; daily life is affected.
- Separate type
The form that develops after a facial palsy
It appears after a previous facial palsy. Here there is mild underlying weakness as well; this detail is important in the assessment.
How is it treated?
This condition is not treated in a dental clinic; the assessment is done by neurology. The dentist's contribution here is limited and clear: to tell by examination that the contraction is not coming from the chewing muscles, and to send you to the right department. Night guards used for teeth grinding, muscle relaxant treatments and dental procedures have no place in this condition.
In neurology the diagnosis is made from your history and the examination. You will be asked which muscle the contraction started in, whether it is one-sided and whether it carries on while you sleep. An MRI scan of the brain may be requested to look for a blood vessel next to the nerve and for other causes; in some cases an electrical nerve test is added.
The treatment options are decided by the doctor. The method used most often is botulinum toxin given into the affected muscles; its effect is temporary and it has to be repeated at set intervals. In selected patients, surgery to separate the blood vessel from the nerve is considered by neurosurgery. Medicines taken by mouth generally give limited benefit.
- Numbness of the face, hearing loss or ringing in the ear appearing alongside the twitching
- The twitching spreading to both sides within a short time, or moving to the arm and leg
- Loss of power in the same area as well, that is, some muscles not working at all
- The eyelid staying closed long enough to block your vision
How is it prevented?
- Caffeine, lack of sleep and long spells in front of a screen can increase an ordinary eye twitch; putting these right first is most of the time enough.
- Record the twitching as a short video on your phone; there may be no contraction during the examination, and this recording makes the assessment easier.
- If the twitching is one-sided and has gone on for weeks, ask for a neurological assessment before you go looking for a night guard.
- If your vision is being interrupted because the eyelid closes, talk to your doctor about driving until the assessment is complete.
Frequently asked questions
- Is the twitch in my eyelid hemifacial spasm?
- Most of the time it is not. Eyelid twitching that comes with tiredness, lack of sleep, caffeine and stress is very common, can be seen in both eyes and generally goes away by itself. If the twitching is on one side only, if it lasts for weeks, if it spreads to the cheek or if it continues during sleep, an assessment should be asked for.
- Is a night guard made for this?
- A night guard is a device used for clenching and grinding; there is no benefit expected from it in hemifacial spasm. Because the contraction comes from the muscles of expression rather than the chewing muscles, treatments aimed at the jaw joint are not expected to give a result. Making this distinction early prevents unnecessary treatment.
- Could stress be causing this twitching?
- Stress, tiredness and excitement can increase how often the contractions come and how strong they are; most people notice this. But stress on its own is not counted as the cause of the condition. The underlying condition needs to be investigated, and advice aimed only at resting should not be settled for.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.