Synkinesis: Everything You Need to Know

Synkinesis is an abnormal pairing of muscle movements that are not normally paired. Facial synkinesis is the most common type. It causes a movement pattern of the face in which a person will have involuntary (not on purpose) movements of one or more facial muscles when they voluntarily (on purpose) move another part of the face.

For example, the eye might twitch when a person smiles. This occurs due to irregular healing and regeneration of the nerves that control facial movements after they have been damaged.

Sometimes the symptoms of synkinesis can be mild and might not require treatment. If the symptoms are very noticeable and distressing, there are treatments that can help alleviate the involuntary facial movements.

This article will discuss the causes of synkinesis, symptoms, diagnosis, and treatment.

Synkinesis Causes

The facial nerve (cranial nerve 7) controls the muscles of the face. Facial nerve branches and facial muscles are small, which results in a range of facial expressions. For example, the facial nerve branches that allow you to smile are different from those that enable you to puff out your cheeks. 

Synkinesis occurs when facial nerve branches regrow towards different groups of muscles that aren’t normally controlled by the same nerve. For example, the nerve that controls smiling might also begin to control the muscles that close your eyes.

The nerve regeneration of synkinesis occurs after the facial nerve or some of its branches have been damaged by trauma, a tumor, inflammation, or an infection. 

Causes include:

• Ramsey Hunt syndrome: This complication of shingles (a painful rash due to reactivation of the virus that causes chickenpox) results in facial nerve weakness.
• Bell’s palsy: This temporary condition causes loss of facial nerve function, often after an infection or inflammation.
• Cancer: A tumor can grow into the nerve or muscles of the face. 
• An abscess: This walled-off pocket of pus and bacteria may begin with a dental infection, or it can be due to trauma of the mouth or face.
• An injury to the facial nerve: An injury may cut the facial nerve or some of its branches.
• Congenital (from birth) defect: One or more nerves, including the facial nerve, might be defective from birth.

The muscles that control facial movements can also become damaged when a nerve is damaged—such as when there’s trauma to the face. And sometimes, prolonged denervation (lack of nerve stimulation) can lead to muscle atrophy (shrinking) so that the muscle will not move normally, even when stimulated by a nerve. 

Synkinesis Symptoms

Normally, some muscles in the body move together, even when you are not thinking about moving them together. For example, smiling often causes both eyes to squint just a little. 

With synkinesis, the coordination and pairing of muscle movements are abnormal. When you voluntarily move certain muscles of the face, for example, other muscles that aren’t normally paired will move involuntarily and abnormally. 

In general, the involuntary movements of synkinesis only affect one side of the face because the damage that causes the condition typically affects one nerve or one side of the face. 

Sometimes synkinesis can be severe and may cause a very noticeable abnormal pattern of facial movement. This can make a person self-conscious, and it can make others confused about the person’s facial expressions. 

Efforts to compensate for the facial movements may be effective if the condition is mild. Overcompensating for facial movements can cause anxiety and may cause physical discomfort or muscle spasms.

Diagnosis

Synkinesis is diagnosed based on physical observation, medical history, and sometimes diagnostic testing. 

If you have noticed or have been told that you have unusually coordinated facial movements, you should see a healthcare provider. During your physical examination, you will be asked to move your face so the movement pattern can be observed. 

Diagnostic tests may include:

• Imaging test if there is concern about a tumor or other growth in the tissue of the face 
• Blood tests if there is concern about an infection 
• Electromyography (EMG) or nerve conduction study (NCV) to test the function of the nerves and muscles and to identify which nerves and muscles are affected

Synkinesis Treatment

There are options for treatment of facial synkinesis. They can include physical therapy, Botox (botulinum toxin) injection, pain medication, or surgery. 

Treatments can include:

• Physical therapy techniques can involve neuromuscular retraining exercises (exercises that train nerves and muscles to communicate) and biofeedback (electrical signals from muscles help the person learn to control the muscles).
• Medication can include oral muscle relaxants.
• Injections of botulinum toxin can paralyze muscles, preventing movement of a targeted muscle group.
• Surgery involves cutting branches of an affected nerve to prevent the unwanted movements.

Therapy may involve one or more of these options. For example, botulinum toxin or muscle relaxants may be needed in smaller amounts after surgery. And physical therapy may be necessary along with these treatments.

Summary 

Synkinesis is a nerve disorder that occurs when nerves heal in an abnormal anatomical pattern after an injury. With synkinesis, a single nerve stimulates more than one muscle to produce movements that don’t normally occur together. Common causes include Ramsey Hunt syndrome, Bell’s palsy, facial nerve trauma, and more.

Certain medical and surgical interventions can help improve the appearance of the face to give an appearance of facial symmetry and prevent unwanted muscle movements, but treatment may not completely resolve abnormalities of facial movements.
 

A Word From Verywell 

It can be stressful to lose control of your muscle movements, especially since facial movements are an important aspect of non-verbal communication. Often, facial synkinesis is a long-term complication that follows a bout of facial weakness, such as Bell’s palsy.

The condition can range from mild to severe. Recovery is not easy, but it is possible to improve your facial appearance and muscle control with therapy, medication, or surgery.