Synkinesis

Original Editor - Wendy Walker

Lead Editors  

Introduction & Definition

Synkinesis (AKA aberrant regeneration) occurs after injury to the facial nerve, as a common sequelae of facial palsy.

The cause of the injury may be simple Bell's Palsy, the less common condition Ramsey Hunt Syndrome, surgical damage (eg. during surgical removal of Acoustic Neuroma) or trauma (skull fractures).

Synkinesis = "syn" meaning "together and "kinesis" meaning movement. Therefore synkinesis means "moving together" or "mass movement".

Synkinesis is an involuntary movement accompanying a voluntary one.  

The type of synkinesis is commonly described by combining the names of the two involved muscle groups, with the first part referring to the voluntary motor group followed by the involuntary muscle group. For instance, ocular-oral synkinesis = when voluntary eye contraction such as blinking or brow lifting elicits an involuntary mouth movement; and oral-ocular synkinesis - when involuntary eye contraction accompanies volitional mouth movement such as smiling and lip puckering.

Clinically Relevant Anatomy

The facial nerve is the 7th cranial nerve, and it controls the muscles of facial expression.

Refer to the Facial Nerve page for more details of its anatomy. 

Mechanism of Injury / Pathological Process

The unintentional or mass movements are thought to be caused by an undifferentiated regeneration of the facial nerve that occurs after being compressed or damaged.

There are 3 possible mechanisms which it is thought could be the cause of synkinesis:

  1. Aberrant regeneration[1][2][3] "miss-wiring"  (axons project from the facial nucleus to incorrect peripheral muscle groups)
  2. Ephaptic transmission[4] (electrical cross-talk between nerve branches)
  3. Nuclear hyperexcitability[5][6]

It is possible that a combination of 2 or all 3 of these mechanisms is involved.

Clinical Presentation

Following flaccid facial palsy, as the patient experiences recovery and reinnervation of the affected side of the face, they also experience the involuntary linking of movements which are typical of synkinesis.

The effects which are most commonly observed[7] are:

  1. when moving the mouth (eg. smile, lip pucker, when eating) the eye on the affected side moves towards partial (or occasionally full) closure, whereas the unaffected eye remains wide open = oral-ocular
  2. when raising the eyebrows or closing the eyes, the corner of the mouth on the affected side of the face raises = ocular-oral

It is important to recognise that synkinesis frequently starts to occur from the 5th or 6th month post onset of palsy, although in some instances it can present as early as the 3rd month post onset, and generally increases for up to 2 years post onset[8][9].

Scoring/measuring synkinesis

The most commonly (by surgeons and physicians) used measure of facial range of movement is the House-Brackmann scale[10]

Unfortunately, this does not have a rating for the aberrant linking of movements which occur in synkinesis.

The Sunnybrook Facial Grading System [FGS][11] is a more comprehensive scoring system for facial range of movement, and it has a section dedicated to rating the presence of synkinesis movements[12]. A recent systematic review[13] of facial nerve grading systems identified the Sunnybrook Facial Grading System as meeting the most criteria in regards to overall assessment of facial nerve function, sequelae, and response to treatments, and having the highest reliability.

The Synkinesis Assessment Questionnaire consists of 9 questions and has been shown to be both valid and reliable as a dedicated measurement of synkinesis[14]; it has also been shown to have good correlation with
the synkinesis component of the Sunnybrook FGS.

The authors of this article, Postparalysis Facial Synkinesis: Clinical Classification and Surgical Strategies, have formulated a novel classification system, with 4 categories:

  • Pattern I    Good smile (ie good range of movement) with mild synkinesis
  • Pattern II   Acceptable smile with moderate to severe synkinesis
  • Pattern III  Unacceptable smile (little or no range of movement) with severe synkinesis
  • Pattern IV  Poor smile with mild synkinesis

This method of scoring synkinesis does not have inter and intra-rater reliability studies, but it proved useful in the study for deciding on management.

Management / Interventions

Physiotherapy interventions

The following physiotherapy interventions have been shown to be effective in reducing or minimising synkinesis:

Non-physiotherapy interventions

  • Botulinum Toxin injections[19][20]
  • Surgery - this is used very infrequently, and usually for severe synkinesis which has failed to respond  to physiotherapy and Botox. The surgeries used include: selective neurolysis[21],  selective myectomy[22] and even cross-facial nerve grafting[23]

Differential Diagnosis

Synkinesis is a clinical diagnosis, and is usually easy to diagnose as the patient will demonstrate clear linking of facial movements on the affected side only, and will have a history of facial palsy.

Occasionally it can be confused with the following conditions:

  • Facial dystonia
  • Essential blepharospasm
  • Essential hemifacial spasm

Resources

The Facial Palsy UK charity has a comprehensive website, and this is the page explaining more about synkinesis.

Recent Related Research (from Pubmed)

References

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  1. Moran CJ, Neely JG. (1996). "Patterns of facial nerve synkinesis.". Laryngoscope 106 (12): 1491–6
  2. Choi D, Raisman G. (2004). "After facial nerve damage, regenerating axons become aberrant throughout the length of the nerve and not only at the site of the lesion: an experimental study.". Br J Neurosurg. 18 (1): 45–8
  3. Yamada H, Hato N, Murakami S, et al. Facial synkinesis after experimental compressionfckLRof the facial nerve comparing intratemporal and extratemporal lesions. LaryngoscopefckLR2010;120:1022-1027
  4. Sadjadpour K. (1975). "After Postfacial palsy phenomena: faulty nerve regeneration or ephaptic transmission?". Brain Res. 95 (2-3): 403–6
  5. Sibony PA, Lessell S, Gittinger JW Jr. (1984). "Acquired oculomotor synkinesis.". Surv Ophthalmol. 28 (5): 382–90
  6. Husseman J, Mehta RP. Management of synkinesis. Facial Plast Surg 2008;24:242-249
  7. Frequency and location of synkineses in patients with peripheral facial nerve paresis.fckLRBeurskens CH1, Oosterhof J, Nijhuis-van der Sanden MW
  8. Comparison of facial synkinesis at 6 and 12 months after the onset of peripheral facial nerve palsy.fckLRFujiwara K1, Furuta Y2, Nakamaru Y3, Fukuda S3. Auris Nasus Larynx. 2015 Feb 2
  9. Pourmomeny, AA and Asadi1, S. Management of Synkinesis and Asymmetry in Facial Nerve Palsy: A Review Article. Iran J Otorhinolaryngol. 2014 Oct; 26(77): 251–256.
  10. House JW, Brackmann DE (1985). "Facial nerve grading system". Otolaryngol Head Neck Surg 93: 146–147
  11. Otolaryngol Head Neck Surg. 1996 Mar;114(3):380-6.fckLRDevelopment of a sensitive clinical facial grading system.fckLRRoss BG1, Fradet G, Nedzelski JM.
  12. Laryngoscope. 2010 May;120(5):1038-45. doi: 10.1002/lary.20868.fckLRSunnybrook facial grading system: reliability and criteria for grading.fckLRNeely JG1, Cherian NG, Dickerson CB, Nedzelski JM
  13. Fattah AY, Gurusinghe AD, Gavilan J, et al. Facial nerve grading instruments: systematicfckLRreview of the literature and suggestion for uniformity. Plast Reconstr Surg 2015;135:569-fckLR579
  14. Mehta RP, WernickRobinson M, Hadlock TA. (2007). "Validation of the Synkinesis Assessment Questionnaire.". Laryngoscope. 117 (5): 923–6
  15. Brach JS, VanSwearingen JM, Lenert J, Johnson PC. (1997). "Facial neuromuscular retraining for oral synkinesis.". Plast Reconstr Surg. 99 (7): 1922–31
  16. Manikandan N. (2007). "Effect of facial neuromuscular re-education on facial symmetry in patients with Bell's palsy: a randomized controlled trial.". Clin Rehabil.. 21 (4): 338–43
  17. Ross B, Nedzelski JM, McLean JA. (1991). "Efficacy of feedback training in long-standing facial nerve paresis.". Laryngoscope. 101 (7): 744–50
  18. Int Rehabil Med. 1982;4(2):67-74.fckLRFacial paralysis rehabilitation: retraining selective muscle control.fckLRBalliet R, Shinn JB, Bach-y-Rita P
  19. de Maio M, Bento RF. Botulinum toxin in facial palsy: an effective treatment forfckLRcontralateral hyperkinesis. Plast Reconstr Surg 2007:120;917-927
  20. Filipo R, Spahiu I, Covelli E, Nicastri M, Bertoli GA. Botulinum toxin in the treatment offckLRfacial synkinesis and hyperkinesis. Laryngoscope 2012;122:266-270
  21. Selective neurolysis in post-paralytic facial nerve syndrome (PFS). Bran GM, Lohuis PJ. Aesthetic Plast Surg 2014;38:742-744
  22. Selective myectomy for postparetic facial synkinesis. Guerrissi JO. Plast Reconstr Surg 1991;87:459-466
  23. Zhang B, Yang C, Wang W, Li W. Repair of ocular-oral synkinesis of postfacial paralysis using cross-facial nerve grafting. J Reconstr Microsurg 2010;26:375-380