What is Hemifacial Spasm?

Medically Reviewed by Dan Brennan, MD on June 08, 2021

‌Hemifacial spasm is a disorder of the nerves and muscles that causes nonpainful involuntary twitching on one side of the face. Many people refer to hemifacial spasms as lip muscle spasms. 

Hemifacial spasms are usually caused by a blood vessel pressing on a facial nerve. They may also be caused by a tumor or a facial nerve injury. Lip muscle spasms can be treated with Botox injections or surgery.

What are the Symptoms?

‌The first symptom of hemifacial spasm is usually a twitching of the eyelid muscle that comes and goes. This twitching often starts in the lower eyelid. The spasms may spread to your cheeks and lips over time. Eventually, the spasms may involve all of the muscles on one side of your face, causing it to twitch involuntarily. The spasms can also cause your mouth to be pulled to one side. 

In certain rare cases, people have twitching on both sides of their face. The twitching is usually intermittent at first, meaning that it comes and goes, but it can become almost constant as the condition progresses. Your symptoms may also worsen when you are stressed or tired.

Hemifacial spasms are painless but can be embarrassing for those affected.

What Causes Hemifacial Spasm?

‌‌Hemifacial spasms are usually caused by a blood vessel pressing on the facial nerve near where it exits the brainstem. In some cases, hemifacial spasms are caused by a facial nerve injury or a tumor.

Facial nerves control the movement of muscles in the face, and the pressure of the blood vessel or the tumor on the nerve causes signals in the nerve that aren’t sent by the brain. These signals cause the involuntary muscle twitching in the lips and face.

Who is at Risk of Lip Muscle Spasms?

‌Hemifacial spasm is a rare disorder. Men and women of any age can get hemifacial spasm, but it is most common in 40-year-olds to 79-year-olds. This disorder is also almost twice as common in women (0.0074% of men and 0.014% of women). Middle-aged and elderly women are the most often affected by hemifacial spasm. It is also much more common in Asian populations.

How are Hemifacial Spasms Diagnosed?

‌Your doctor will perform a physical examination to check for signs of hemifacial spasm, for example, lip muscle spasms. Magnetic resonance imaging (MRI), which uses powerful magnets, radio waves, and a computer to capture a detailed image of your head, is then used to determine the most appropriate form of treatment.

Magnetic resonance imaging is used to identify the blood vessel pressing against the nerve and to make sure that the spasms aren’t caused by other conditions with similar symptoms, such as structural abnormalities, tumors, or multiple sclerosis.

How are Lip Muscle Spasms Treated?

‌There are several types of treatment for hemifacial spasms. The treatment that your doctor selects will depend on the cause and severity of your condition. Treatments for hemifacial spasm include:

Botox (botulinum toxin) injections. Botox injection is the most commonly used and the most effective treatment of hemifacial spasm. To relieve the spasms, your doctor will inject Botox into the affected muscles to paralyze them. This treatment will need to be repeated every few months.

Microvascular decompression surgery. If your disorder is more severe, your doctor may recommend microvascular decompression surgery. In this surgery, your surgeon opens the hard layer covering your brain to locate the blood vessel that is pressing on your facial nerve. Your surgeon then places a small sponge between the nerve and blood vessel to reduce the pressure on the nerve. This surgery is effective in reducing spasms, but it has several possible side effects and so it is only done if botox injections aren’t effective enough in reducing the symptoms.

‌Medications. In some cases, medications, such as anticonvulsant drugs (e.g., carbamazepine and clonazepam), can reduce lip muscle spasms.

What Else May Cause Lip Muscle Spasms?

‌Several other conditions can cause facial twitching similar to hemifacial spasms. ‌If your doctor determines that your facial twitching isn’t caused by the pressure of a blood vessel or tumor on your facial nerve, you should consider these other possible causes of facial twitching. The following conditions can cause twitching in your eyes, lips, or cheeks:

  • Caffeine intoxication, which happens when a healthy adult consumes over 400 milligrams a day.
  • Medications that list “fasciculation”, which means involuntary muscle contractions, as a side effect.
  • Stress and fatigue.
  • Bell’s palsy — an unexplained instance of facial muscle weakness or paralysis.
  • Parkinson’s disease.
  • Hormonal imbalance.
  • Multiple sclerosis.

Show Sources


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Elsevier: “Bradley's Neurology in Clinical Practice: Parkinson disease and other movement disorders.”

Frontiers in Psychiatry: “The safety of ingested caffeine: A comprehensive review.”

GeneReviews: “Parkinson disease overview.”

JAMA Neurology: “Hemifacial Spasm in Rochester and Olmsted County, Minnesota, 1960 to 1984.”

Journal of the neurological sciences: “Asian over-representation among patients with hemifacial spasm compared to patients with cranial-cervical dystonia,” “Hemifacial spasm: The past, present and future.”

‌Mayo Clinic: “Hemifacial spasm.”

‌Merck manual: “Hemifacial spasm.”

Movement Disorders: “The many faces of hemifacial spasm: differential diagnosis of unilateral facial spasms.”

‌National Institute of Neurological Disorders and Stroke: “Bell's palsy fact sheet,” “Hemifacial Spasm Information Page.”

The Journal of Clinical Endocrinology & Metabolism: “Management of hypoparathyroidism: Summary statement and guidelines.”

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