Facial synkinesis

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Facial synkinesis (synkinesia[s]) occurs after a lesion disrupts CN VII axonal continuity and regenerating fibers grow into the wrong endoneurial tubes. Axons that originally innervated the upper face, especially the orbicularis oculi, are redirected into the lower face, particularly the orbicularis oris, and vice versa. This aberrant regeneration results in cocontraction of facial muscles with voluntary effort. If the patient attempts to close the eye, the mouth twitches. (1) If the patient smiles, the eye may blink. When severe, smiling or laughing or opening the mouth may cause simultaneous spasmodic closure of the eye. In some instances there is ptosis of the eye on smiling or opening the mouth (Marin Amat sign, inverse jaw winking).(2,3) At other times, the synkinetic movements are very subtle. The most common cause of facial synkinesis is Bell's palsy, but it can occur after any facial nerve injury. The most common form is oculo-oral, subtle perioral movements synchronous with blinking.

Facial synkinesis and hemifacial spasm are at times difficult to distinguish. The difference is that with hemifacial spasm there is simultaneous contraction of the entire face that is completely beyond the patient's voluntary control. With facial synkinesis, there is contraction of the aberrantly innervated muscle group with the voluntary contraction of the other muscle group; involuntary contraction of one muscle is simultaneous with voluntary contraction of a different muscle. Hemifacial spasm is completely involuntary. Facial synkinesis can be voluntarily suppressed for a period of time, at least as long as one could voluntarily inhibit blinking. Asking the patient to blink produces the cocontraction of the orbicularis oris, asking the patient to smile produces the cocontraction of the orbicularis oculi.


1. Campbell WW. Clinical signs in neurology : a compendium. Philadelphia: Wolters Kluwer Health, 2016.

2. Malhotra A. Marin-Amat syndrome: a case of acquired facial synkinesis. BMJ Case Rep. 2013 Jul 18;2013.

3. Mansoor AM, Sullivan PD. Intrafacial Synkinesis. N Engl J Med. 2016 Jun 2;374(22):e27.