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BackTable / ENT / Article
Synkinesis Explained: A Facial Plastics Perspective
Julia Casazza • Mar 6, 2024 • 39 hits
Patients dealing with synkinesis experience unintentional facial movement, pain, and facial asymmetry. While the pathophysiology of this condition remains incompletely understood, most surgeons believe injury to the facial nerve followed by aberrant reinnervation causes symptoms. Recently, facial plastic surgeon Dr. Shiayin Yang, Assistant Professor at Vanderbilt University, advised BackTable listeners on how to think about and counsel patients on this condition.
This article features excerpts from the BackTable ENT Podcast. We’ve provided the highlight reel in this article, but you can listen to the full podcast below.
The BackTable ENT Brief
• Synkinesis is a variety of non-flaccid facial paralysis in which voluntary facial movement triggers involuntary facial movement. Patients may also report facial hypokinesis.
• The pathophysiology of synkinesis remains incompletely understood. The most widely accepted theory posits that injury to the facial nerve causes nerve branches to regrow and innervate the wrong muscle fibers.
• The most common cause of synkinesis is Bell’s Palsy – idiopathic facial paralysis with onset within 72 hours. Less common causes include vestibular schwannoma, metastasis to the facial nerve, temporal bone trauma, and injury during surgery.
• Initial evaluation of synkinesis consists of a history and head and neck exam. Labs and imaging are not routinely needed.
Table of Contents
(1) Synkinesis Definition
(2) Explaining Synkinesis to Patients
(3) Initial Evaluation of Synkinesis
Synkinesis Definition
Synkinesis is involuntary facial movement accompanying voluntary facial movement. Strictly speaking, it exists on the non-flaccid facial paralysis spectrum, which includes both involuntary facial movement and facial weakness. Though associated with Bell’s palsy, synkinesis can develop following any facial nerve trauma, including acoustic neuroma surgery, or temporal bone trauma.
[Dr. Shiayin Yang]
Synkinesis is actually part of a spectrum, which is called post-paralytic facial paralysis or non-flaccid facial paralysis, and it occurs after there's any type of facial nerve injury. I think a lot of people hear synkinesis and they think it's something that happens just after Bell's palsy, but it can happen after any type of injury to the nerve.
If there's been traumatic injury after like temporal bone trauma, or if the nerve has been transected during surgery due to a malignancy, like a parotid malignancy, or if it's stretched or injured during removal of acoustic neuroma, you can get synkinesis after these situations as well, or these scenarios, and I think that's something that is important to understand. Synkinesis itself, the definition is involuntary movement of facial muscles with voluntary facial movement.
If you're thinking-- more commonly you see a patient and they say, "Every time I close my eye, my mouth moves, or every time I smile, I get a contracture in my neck, or my eye closes," that's our fundamental thinking of what synkinesis is, but really this picture of this non-flaccid facial paralysis is a combination. You can have synkinesis where patients are having this involuntary movement of the facial muscles, but you can also have this mixed picture where some patients have weakness. Usually we'll see that a lot in the lower lip. They'll have elevation of their upper lip and their DAO [Depressor Anguli Oris] is not contracting to bring that for that dental show of their lower lip, and so you're not getting that natural smile.
Some patients will have this hyperkinesis or they're contracting more on a certain part of the face, and so they'll have these deep nasolabial folds. They'll complain of significant tightness or pain around the neck. It's more a constellation of symptoms and signs that's included in synkinesis that patients can have after any type of facial nerve injury.
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Explaining Synkinesis to Patients
Bell’s Palsy – idiopathic hemifacial paralysis that often self-resolves – represents the most common cause of synkinesis. In many cases, patients will experience Bell’s palsy, recover, and then have a recurrence of their facial paralysis 6-18 months later. Overall, about 10-30% of Bell’s palsy patients later develop synkinesis [1]. Less common (though important) causes of synkinesis include temporal bone fracture, facial nerve neuroma, and metastasis to the facial nerve.
Dr. Yang advises primary care physicians to provide facial plastic surgery referrals for all suspected Bell’s palsy patients. This allows her to rule out more serious conditions that both mimic Bell’s palsy and, in many cases, also cause synkinesis. When counseling a new patient, she advises them they are unlikely to return to their previous baseline for facial expression. She then explains that the pathophysiology of the condition isn’t completely understood, but that most treatments (including physical therapy and botulinum toxin injection) aim to correct aberrant innervation following injury.
[Dr. Shiayin Yang]
The most common patient presentation is Bell's palsy. I think that is why this podcast is so important and education is so important because a lot of the patients I see develop synkinesis much later. Synkinesis can develop anywhere between 6 to 18 months after your initial injury. You get Bell's palsy, let's say you recover movement of your face, you see your primary care provider or whoever it is that was managing it and they're like, "Oh, well, your facial function is back." Then six months later, you start noticing these involuntary movements or you're having issues with eye function or smile, speaking, eating, and you may not be following with that person anymore.
…
Unfortunately, since we don't know how the nerve regenerates, we don't have a perfect treatment for it. All of our subsequent treatments for facial nerve paralysis is based on what the patients are experiencing and not actually fixing. We don't truly understand the pathophysiology. Since we don't 100% know the pathophysiology, we don't know how to restore them back to their pre-paralysis state.
It's understanding that and really setting expectations that I'm going to do my best to give you the best smile you need or help you close your eyes best as possible. It is very difficult, well, near impossible to get you back to where you were before. That's a huge part of the understanding. Next, I discussed that the most common theory in terms of pathophysiology is there's some sort of aberrant rewiring of the nerve as it's growing back to its distal branches. The facial nerve, as we know, comes from the brainstem, routes through temporal bone out into the parotid gland, and then branches into multiple branches onto the face to innervate the multiple facial muscles that there are.
Initial Evaluation of Synkinesis
Evaluation of patients with synkinesis is straightforward. Dr. Yang performs a full head and neck exam, paying close attention to the ear so she can spot pathologies (such as cholesteatoma) that could compromise facial nerve function. When taking a history, she pays close attention to timing; to diagnose Bell’s palsy, facial paralysis must onset within 72 hours. In cases where she suspects lateral skull base pathology, she obtains an MRI of the internal auditory canal (IAC) with contrast. She does not routinely order labs.
[Dr. Shiayin Yang]
Full head and neck exam, looking at doing a good otologic exam, making sure there's nothing within the middle ear or within the ear that could be causing the spatial nerve paralysis, looking at their parotid gland, any history of skin cancer, doing a full head and neck exam to make sure there's no lesions or bumps, and then doing a neurologic exam as well as a full cranial nerve exam. History is important because that's going to clue you in if it's, "Yes, that sounds like a Bell's palsy." These patients are sudden within 72 hours onset of partial or complete paralysis on that face.
Usually those patients say, "Hey, doc, I woke up, and the next morning my face was out." Compared to someone who's saying, "Oh, my face slowly went out, but then I regained function, and then a couple months later it got weaker again," that's an indication it's not Bell's palsy. Additionally, patients who only have partial weakness of one branch or two branches, that should also be an indication that maybe these aren't Bell's palsy patients. Anyone who's had recurrent facial paralysis on one side or bilateral facial paralysis, that is very rare with Bell's palsy.
Or if it's someone who said, "Oh, I was diagnosed with Bell's palsy," they're seeing you four to six months later and their face is completely out. Those are warning signs that it's not Bell's palsy, and in any of those cases, you should do additional workup. If it seems like it's the pretty straightforward Bell's palsy diagnosis, sudden onset, no other warning signs, then typically you do not need additional workup for those patients. We have a great guideline put out by the Academy in terms of Bell's palsy that can really help guide providers just on what's the current recommendations by the Academy.
Typically I won't do additional workup unless I'm concerned or something seems off. If I'm concerned, then it's an MRI IAC with contrast to look at the full course of the facial nerve. Sometimes I'll additionally get labs just to see if there's other causes that could be leading to this paralysis.
Podcast Contributors
Dr. Shiayin Yang
Dr. Shiayin Yang is an assistant professor of facial plastic and reconstructive surgery with Vanderbilt University in Nashville, Tennessee.
Dr. Ashley Agan
Dr. Ashley Agan is a practicing ENT and assistant professor at UT Southwestern Medical Center in Dallas, TX.
Cite This Podcast
BackTable, LLC (Producer). (2023, December 26). Ep. 151 – Navigating Synkinesis: From Diagnosis to Comprehensive Care [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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