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Overview of Hemifacial Spasm

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Involuntary twitching of the muscles of the face caused by irritation of the facial nerve is called hemifacial spasm; these spasms are not generally painful. The muscles of the face that help us smile, frown, raise our eyebrows, and perform all other facial expressions are controlled by the facial nerves; each side of the face has its own facial nerve.

Hemifacial spasm is the twitching of these muscles for facial expressions, usually on only one side of the face. Compression or irritation of this nerve by a blood vessel, or less commonly a tumor, can cause these spasms. The biggest problem associated with hemifacial spasm is social embarrassment and sometimes interference with vision during driving and other activities.  

Causes of Hemifacial Spasm

The most common cause of hemifacial spasm is an irritating compression of the facial nerve by a blood vessel. This compression usually occurs near the brainstem and causes the facial nerve to transmit abnormal signals to the facial muscles, leading to muscle twitching and spasms.

Hemifacial spasm is rarely caused by a brain tumor. Associated symptoms, such as hearing loss, difficulties with balance, and facial pain, should raise the suspicion for a brain tumor. Hemifacial spasm in a younger person could be more indicative of multiple sclerosis, a disease that causes the immune system to attack the protective covering of nerves. Another rare cause is Bell’s palsy, which is a virus-induced inflammation of the facial nerve. In some cases, a cause for the spasms cannot be identified.

Women of Asian descent are at the highest risk of suffering from this condition, and it most commonly affects those who are over 40 years of age. Hemifacial spasm tends to be a commonly misdiagnosed condition, with the average patient experiencing symptoms for around 8 years before receiving the correct diagnosis.

Although there have been a few reports of hemifacial spasm occurring in a single family, it is not considered to be a hereditary condition.

Also, although a few people developed hemifacial spasm after COVID-19 vaccination, there has been no evidence to prove a relationship between vaccination and any type of hemifacial spasm.

Symptoms of Hemifacial Spasm

The typical symptom of hemifacial spasm is twitching of the facial muscles. Although you might be able to feel these spasms, they do not usually hurt. The spasms are also involuntary, meaning that you cannot control them. This condition usually affects only one side of the face; rarely are both sides affected.

The symptoms normally start as an occasional twitch, which gradually progresses to a constant spasm. The eyelids tend to be the first location, with the rest of the facial muscles getting involved over time, including those around the mouth. The spasms can cause awkward facial expressions that can lead to embarrassing moments.

Apart from social discomfort, hemifacial spasm can cause a few other problems. You may find it difficult to sleep because of the constant twitching and spasms. Eyelid spasm can cause vision difficulties. The facial nerve also controls a small muscle in the ear, so you may hear a ticking sound each time you develop a twitch. Because the facial nerve also controls the muscles of the lips, hemifacial spasms might make talking difficult. The symptoms can prove to be very distracting, with some people becoming self-conscious. Stress and/or anxiety can be a trigger and can increase the severity of twitching, although neither of them is the root cause.

Hemifacial spasm is not usually life-threatening, but it is important to have these symptoms evaluated to ensure that the spasms are not being caused by something more serious, such as a brain tumor. In addition, timely treatment through surgery can potentially decrease the chance of permanent weakness caused by repeated use of Botox injections (see below).

Diagnosis of Hemifacial Spasm

If you feel symptoms of hemifacial spasm, it is important to visit a doctor, who can help determine the correct diagnosis. To be sure that the condition is not related to a brain tumor, your doctor will ask you a few questions about your symptoms and perform a physical examination. This exam will involve the doctor testing the strength of your facial muscles by making you demonstrate various facial expressions. You also might be asked to undergo a magnetic resonance imaging (MRI) scan to make sure there is nothing serious causing the symptoms. Most people with hemifacial spasm will have a blood vessel pressing on the facial nerve; on rare occasion, the cause will be found to be a brain tumor.

A special high-resolution brain MRI may be necessary to detect the small vessel pressing on the nerve as the regular MRI may not detect the compression.

It is of utmost importance for your doctor to rule out any other conditions that mimic hemifacial spasm. For example, fasciculations are occasional involuntary small muscle movements that generally affect the eyelid. However, these twitches are not generally strong enough to alter facial expressions.

Facial myokymia is a condition characterized by a rippling of multiple facial muscles that causes worm-like quivering movements under the skin of the face. Facial myokymia usually subsides within a few months.

Blepharospasm is another disorder that can be confused for hemifacial spasm. Its symptoms usually involve repeated, excessive, and involuntary blinking. The difference from hemifacial spasm is that with blepharospasm, symptoms are restricted to the muscles around the eyes, and they disappear during sleep.

The diagnosis of hemifacial spasm requires a high degree of clinical suspicion, so it is important to visit a neurosurgeon with considerable experience in the field.

Treatment of Hemifacial Spasm

Hemifacial spasm can be treated by medications, injections of onabotulinumtoxin A (Botox, Allergan Aesthetics, Irvine, CA), or surgery. Although medication and Botox injections only provide relief for the symptoms, surgery is focused on correcting the root cause of the problem.


Available medications work by reducing the reactivity of the facial nerve to electrical stimuli, leading to a decrease in the number and severity of the twitching and spasms. The most commonly used medicines include carbamazepine (Tegretol), clonazepam (Klonopin), baclofen (Gablofen), and gabapentin (Neurontin).

Some of the side effects of these medicines can include fatigue and poor performance. Other side effects can include sleepiness and skin rashes.

If you have any questions regarding the side effects of any medication or if you have certain allergies, it is a good idea to discuss them with your doctor.

If symptoms are not relieved with medication, you can opt to undergo Botox injections or surgery, depending on the advice of your doctor.

Medications are often not effective to treat hemifacial spasms.

Botox Injections

Botox is popularly used to reduce facial wrinkles, and the same injections used to treat hemifacial spasm work on the same principle. The botulinum toxin in the injection paralyzes the facial muscles, making them unresponsive to electrical signals from the facial nerve. Botox is injected into the muscles of the side of the face that has the spasms. Each injection usually lasts for 3 to 6 months, so more injections are needed after the effects wear off.

The spams may recur more frequently and earlier as time goes by, and more injections are done. The gradual return of spasms can be bothersome to many patients at the end of each cycle of Botox injection, leading patients to seek more definitive solution via surgery. Moreover, long term Botox injection may lead to permanent facial weakness and cosmetic deformity that is unacceptable to many patients. Therefore, early surgery should be strongly considered.


Surgery for hemifacial spasm is called microvascular decompression. It usually involves inserting a piece of cushion between the facial nerve and the blood vessel compressing it. The surgeon usually makes an incision at the back of the head, behind the ear, enters the skull, and gently mobilizes the blood vessel off of the facial nerve to relieve the pressure between them. A large majority of patients (up to 80%) feel an improvement in symptoms after the surgery that is durable for many years to come.

A neurosurgeon with extensive experience in this surgery can minimize the risks of surgery and provide best results.

In this video, Dr. Cohen describes the techniques for surgery to treat hemifacial spasm. 

For more information about the technical aspects of the surgery and extensive experience of Dr. Cohen, please refer to the chapter on Microvascular Decompression for Hemifacial Spasm in the Neurosurgical Atlas

Hemifacial spasm can cause significant, anxiety, depression, and stress. It can help to practice meditation, yoga, or other relaxation techniques. Talking to family and friends about the condition might also make you feel more at ease. Especially important is to talking with a specialist (neurosurgeon) who can help guide you through the treatment for this condition.

Key Takeaways

  • Hemifacial spasm is the painless, involuntary twitching of the muscles on one side of the face.
  • It is usually caused by a blood vessel that compresses the facial nerve; in rare cases, it can be caused by a brain tumor, Bell’s palsy, or multiple sclerosis.
  • It is important to get a formal assessment by a neurosurgeon to identify the cause and differentiate it from other similar conditions. This will allow early diagnosis and treatment while avoiding the side effects of the treatment.
  • Treatments include medication, Botox injections, and surgery. Surgery is the only definitive treatment in patients with the correct diagnosis.