Some patients who have had Bell’s palsy or other reversible forms of facial nerve injury may go on to develop synkinesis. Synkinesis describes unwanted contractions of the muscles of the face during attempted movement. Most commonly, patients will notice forceful eye closure when they attempt to smile, or other muscle spasms during routine facial movements. It is essentially a “faulty re-wiring” of the facial nerve that occurs after injury and recovery. It can be very distressing to patients and may significantly impact quality of life by impairing emotional expression and other essential facial functions. It may even cause facial discomfort or pain.
Synkinesis is diagnosed by a history and physical examination. The incidence of synkinesis is difficult to estimate, since very mild synkinesis may not be easily noticed by physicians or even by patients. However, the incidence is likely determined by the anatomic location of the facial nerve injury, as well as the severity of the injury:
Table from Pepper1
Facial rehabilitation for facial paresis and synkinesis
Facial neuromuscular retraining is the name given to a specialized form of rehabilitation that is unique to facial dysfunction. Specialized therapists educate patients in appropriate exercises and a treatment regimen to maximize their desired facial movement2. This is often an important addition to many forms of facial nerve paralysis treatment, both surgical and nonsurgical.
Botulinum toxin chemodenervation:
Synkinesis that does not respond completely after facial neuromuscular retraining may benefit from targeted injections of botulinum toxin to ease facial muscle spasm. This method of treating synkinesis has been shown to significantly improve symptoms of synkinesis via a randomized clinical trial3,4. Is important to realize that the effects of botulinum toxin are temporary, and repeat treatment every 3-4 months is usually required.
 Pepper JP. Facial Paralysis and Facial Reanimation. Facial Plastic and Reconstructive Surgery: A Comprehensive Study Guide. 2016 Apr 6:109.
 Beurskens, C.H. and P.G. Heymans, Physiotherapy in patients with facial nerve paresis: description of outcomes. American journal of otolaryngology, 2004. 25(6): p. 394-400.
 Borodic, G., et al., Botulinum toxin for aberrant facial nerve regeneration: double-blind, placebo-controlled trial using subjective endpoints. Plastic and reconstructive surgery, 2005. 116(1): p. 36-43
 Pepper, J.P., Kim, J.C., Massry, G.G., Selective chemodenervation with botulinum toxin in facial nerve disorders. Operative Techniques in Otolaryngology, 2012. 23(4): p. 297-305