Improving smiles with a new surgical technique to treat facial synkinesis

• Postparalysis facial synkinesis (PPFS) emerges, causing a spectrum of symptoms including tightness around the eye, unwanted movements, such as twitching, closure of the eye when attempting to smile or during eating, and constant contracted muscles in the face and neck often affecting the upper or lower lip.

Synkinesis is perhaps the least discussed – yet likely most common – negative outcome of facial paralysis, regardless of the cause. Depending on the severity, it has significant impact on facial function, facial appearance, and quality of life.

We don’t exactly know why synkinesis develops, but most theories involve abnormal nerve regeneration. To visualize the brain’s message disruption, picture a six-lane highway. Each lane is assigned to one color car: red, yellow, or blue. Then there’s a crash – the inciting incident of paralysis. The cars become jumbled across the lanes. Over time, the debris is cleared away and the highway starts moving again, but not like it used to. Blue cars are in the yellow lane, red cars in the blue lane, and while it’s functional, it doesn’t look or function the same as before the accident.

Microsurgeons in the UT Southwestern Department of Plastic Surgery, led by Dr. Shai Rozen, recently developed a cutting-edge procedure to rebalance the smile following PPFS by focusing on the mentalis muscle, which runs from the lower chin to the lower lip, and the surrounding nerves which innervate it. Our research in surgical synkinesis treatment won the Joint Outstanding Podium Presentation and Best Paper Award 2024 at the American Society of Reconstructive Microsurgery Annual Meeting.

What does facial synkinesis look like?

There are two major categories of facial palsy:

• Flaccid facial palsy causes a “floppy” face with no movement. It may be accompanied by a drooping eyebrow or eyelid and inability to close the eye. Other symptoms include sagging at the corner of the mouth, which can make it difficult to eat and smile.
• Post-paralysis synkinesis is characterized by excessive tone or tension of the facial muscles and uncoordinated movements and muscle contraction. In synkinesis, for example, when your brain tells your facial muscles to smile, the muscles may oppose one another rather than work together, causing dysfunction, involuntary movements, and often exaggerated baseline contraction of the facial muscles.

Although some patients’ faces remain paralyzed, some return to normal function over three months. Most commonly, if one does not regain normal function within three months, but develops some motion, then varying levels of synkinesis will ensue, potentially causing an uneven smile and scrunching eyes. These symptoms can get worse over time due to disruption of signals from the brain to the face and misaligned pathways resulting in uneven muscle tone.

Other symptoms may include:

• Uncontrolled muscle contracture around the eye, cheek, and chin
• Tightness around the eye and in the face and neck, causing discomfort
• Lip and cheek lifting when the eyes are closed
• Watering eyes when eating
• A deeper cheek crease on the affected side of the face

Related reading: How Susan got her smile back

How is facial synkinesis diagnosed and treated?

Synkinesis is characterized by three main components.

1. Constant and uncontrolled contracture of facial muscles: Also referred to as baseline hypertonicity of the facial muscle. Imagine you are in the sunshine without sunglasses and constantly squinting. You can’t see and after a while you might feel discomfort due to prolonged contraction of the muscles around the eyes. In patients with synkinesis, the eye is constantly squinting, the midface is tight and full, and patients notice biting the cheek or lip because the muscles of the inner cheek or chin are tight.
2. Mouth moves when eyes squint or shut. This form of co-contracture is called oral-ocular synkinesis and ocular-oral synkinesis. When a person with synkinesis tries to smile or purse his or her lips, the eyes frequently squint or even close and sometimes the brow moves. During eye closure, the mouth may move. Patients often notice that the synkinetic eye squints or shuts when chewing.
3. Corner of the lip pulls down while trying to smile: This is caused by co-activation of agonist and antagonist muscles – pathologic co-contraction. Envision you curl a barbell by contracting your biceps but the weight won’t move since the triceps muscle is contracting at the same time, performing the same action in the opposite direction.

Patients with synkinesis suffer functional problems from these variables – they can’t smile, they have facial distortion, and some have facial discomfort. Smiling is extremely important. It is how we communicate joy, empathy, love. Facial asymmetry and contracture will often convey a feeling of anger when the person is happy.