Close this search box.

What is Synkinesis?

Facial Synkinesis is one of the most common and devastating complications after long-standing Bell’s palsy. It can have a dramatic effect on one’s life and remain unchanged for many years. That is why in our clinic we focus so much on synkinesis and its recovery. Based on our own research we challenge the commonly accepted cause of synkinesis and the results of our patients prove that it is possible to reduce, and sometimes even fully eliminate synkinesis.

Contents of this article:

Note: This article is also available in a video format in our Bell’s Palsy Video Courses.

Facial synkinesis is an abnormal facial movement pattern.

Synkinesis is an abnormal facial movement pattern that forms during the delayed regeneration of the facial nerve after Bell’s palsy. It manifests as involuntary movements of facial muscles during speaking, smiling or blinking. There are two most common types of synkinesis: oral-ocular synkinesis or ocular-oral.

Facial synkinesis
Examples of facial synkinesis

Oral-ocular synkinesis

It is an involuntary narrowing of the eye fissure during speaking, smiling, puckering the lips or blowing the cheeks. If your eye closes when you attempt to smile or speak, you have oral-ocular synkinesis.

Ocular-oral synkinesis

It is an involuntary movement of the mouth corner that come together with blinking. If your mouth moves on its own when you try to close your eye or blink, then you have ocular-oral synkinesis.

While these two synkinesis types are the most common, it is possible that synkinesis might include other muscles or more than two muscle groups at once. It may involve frontal muscle (raising eyebrows), platysma (surface muscle of the neck) or the circular muscle of the mouth.

To understand more how synkinesis happens and why at Crystal Touch we believe that synkinesis is reversible, we need to take a closer look at its origins.

What causes synkinesis?

Aberrant regeneration – can it really be the cause of synkinesis?

There are several opinions in the medical world about the causes of synkinesis. The most popular (and still controversial) is the theory of aberrant regeneration or simply said, random reconnection of regenerating branches of the facial nerve to the “wrong” muscles. The idea of aberrant regeneration imposes that when the facial nerve fibres are regenerating, they regrow not to the muscles with which they were connected prior to Bell’s palsy, but to random different muscles. The facial nerve fibres that were previously innervating the muscles of the smile group are now innervating some muscle fibres in the eye group.

As a logical conclusion of this theory, Synkinesis is considered to be an irreversible complication of the long-standing Bell’s palsy.

The results of an extensive study and research of facial synkinesis by the specialists at Crystal Touch allow us to conclude that synkinesis is reversible and that the theory of aberrant regeneration with relation to Bell’s palsy is not free from some controversies.

Here are our considerations.

Structure of a nerve
  1. Just as each copper wire inside the telephone cable is insulated and mechanically protected by its own plastic tube, the same is true for axons of the facial nerve. Each axon (nerve fibre) is enclosed in its own “tube” called endoneurium for protection.
  2. Groups of axons that innervate the same facial muscles are grouped into bundles. Each bundle is covered for additional mechanical protection with another, outer “tube” of connective tissue called the perineurium.
  3. After leaving the trunk of the nerve, those bundles form larger or smaller branches of the facial nerve that go to various parts of the face. When Bell’s palsy occurs, the wires (axons) become damaged from compression by the swollen surrounding tissue or from a disrupted blood supply.
  4. However, the trunk and “protective tubes” (endoneurium and perineurium) in this case remain intact. Therefore, regenerating axons can regrow only within the hollow spaces of endoneurium and only towards their “own” targets – respective muscle fibres.

Conclusion: if the trunk of the nerve was not mechanically interrupted, it is physically impossible for regenerating axons to reconnect to the muscles in the different part of the face. Otherwise, the growing axons would have had to overcome two endoneurial and two perineurial tubes to reach the “wrong” muscles. Aberrant regeneration (re-growing to the wrong muscle) can indeed occur, but only if there was mechanical damage to the trunk of the nerve, for example during surgery or as a result of the accident involving a broken temporal bone.

In our video courses and scientific work descriptions, we provide more reasons and visual representations of why we believe aberrant regeneration is not possible.

Synkinesis as a conditioned reflex or why we believe it is reversible

At Crystal Touch clinic, based on our scientific research and the results we have achieved with our patients, we believe that synkinesis is reversible

Let’s take a look at the summary of our scientific presentation on synkinesis which explains what we believe the true cause of synkinesis to be.

How synkinesis happens

1. As we recover after Bell’s palsy, we begin to put more and more effort into producing any facial movements

To produce mimetic signals, our brain summates the signals coming both from emotional and volitional control centres. In our effort to produce any movements on the affected side during the recovery, we keep trying harder and harder to force our face into expressions. Since the nerve has not recovered fully, we do not see any response on our face, and we simply continue to try harder. This forces our brain to use the volitional centre to amplify every mimetic signal going from our brain to the facial muscles via the facial nerve on the affected side. 

2. Muscles-antagonists become involved in every expression

The constant amplification of mimetic signals results in motor overflow – the neuronal excitation in our brain becomes larger and spreads to “neighbouring” neurons, forcing more muscles to contract than intended. To understand what motor overflow is, here is an example. Imagine a heavy athlete, lifting 100 kg of weight. He will not only use his arms to do that, but you will also see his core, legs, neck, and even his facial muscles tensing up, even though they do no help to lift the weight.

The same happens on our face. We analysed photos of 13 facial expressions of over 800 of our patients and observed that during synkinesis, antagonist muscles are contracting together with the muscles that we need to produce a certain facial expression. Antagonist muscles are the muscles that contract in the opposite direction of the main muscle.

Here are two examples. On the first image (Example 1) you can see that when these patients try to squeeze their eyes, the frontalis muscle (forehead), which is the antagonist in this scenario, overpowers the circular muscle of the eye and raises the eyebrow instead of squeezing the eye.

Bell's palsy - closing eyes
Example 1: Squeezing the eyes shut (maximal effort)

On the second image (Example 2), you can see that when these patients smile, together with the zygomatic muscles, their antagonist-muscles, which are m. Depressor Anguli Oris, and also m.mentalis contract, pulling down the mouth corner. This leads to the asymmetric smile.

Bell's palsy - synkinetic smile
Example 2: Broad smile (maximal effort)

So, every time we want to smile, we don’t simply smile, but we SMILE!!, putting all effort possible into it. This effort contracts other facial muscles, that are usually left relaxed, and produces all the unwanted expressions on our face.

On the image below, the woman with synkinesis is trying to smile. The red arrows show the co-contraction of antagonists. By mirroring the images on the affected and healthy side, we can see the intended expression (right side) and the expression that the affected side produces (left side). As we can see from the expression, the affected side involves a lot of effort.

Synkinesis - original (center), mirror healthy side (left), mirrored affected side (right)
Synkinesis – original (center), mirror healthy side (left), mirrored affected side (right)
3. When we start seeing some movements, our brain gradually solidifies this “over-amplification of mimetic signals” into a habit

We keep over-amplifying our facial expressions in the effort to produce at least some response on our face. Once the recovering neurons begin to reconnect with the facial muscle fibres, we begin to see some response to our efforts. The presence of “at least some results” serves as positive feedback to us, and we continue doing that until it becomes automatic. That is how we form a conditioned reflex. 

It develops little by little, as we are trying harder and harder to produce any facial expressions when first movements start to reappear. That is why it is so difficult to avoid synkinesis if our recovery takes a longer time – we keep hoping that the harder we try, the more likely we are to produce any facial expressions. Our brain develops a habit of over-amplifying any facial expression on the affected side.

The good news – as any other conditioned reflex, synkinesis can be reversed by prolonged negative feedback.

Just as positive feedback solidifies a conditioned reflex, correct negative feedback helps to reverse it. It is a complex process that needs well-trained guidance and a specific pattern of inputs and effort. This is what we do with our patients during our working sessions.

Our Neuro-Proprioceptive Rehabilitation method was developed to help reduce synkinesis by using negative feedback. We have managed to achieve significant improvements for our patients with synkinesis and alleviate manifestations of other complications and residuals. That is why we are confident that synkinesis can be reduced.

If you would like to know more about what can be done in your specific situation, speak directly with our specialists during a remote diagnostic session.

Picture of Alex Pashov

Alex Pashov

Co-founder of Crystal Touch clinic and Bell's palsy expert.

Online Bell's Palsy Consultation

Speak online with our specialist, Alex Pashov, one-on-one.

The session’s purpose is to analyse your condition and provide you with detailed answers about your current state and the future prospects of recovery. During the video session, we also share hands-on recommendations that you can start doing on your own to alleviate some issues that you are facing.

Learn more & Register

Image for Bell's Palsy Online Consultation - a screen with a woman sculpting her face

More articles