Synkinesis is a condition where involuntary muscle movements occur with volitional movements due to nerve trauma. Treatment options include surgery, facial retraining, Botox, facial expression therapy, and biofeedback. The two most commonly studied cases are facial and extraocular muscle synkinesis. Conservative treatments are preferred, with surgery reserved for those who do not respond to other treatments.
Synkinesis, a term derived from the prefix “syn-,” meaning together, and the word “kinesis,” meaning motion, refers to a condition in which involuntary muscle movements occur simultaneously with volitional movements. This condition most commonly results from nerve trauma, which can be triggered by inflammation, physical trauma, a neuroma, or surgery. When the healing of a nerve injury is aberrant, miswiring of the nerves occurs and nerve endings innervate muscles that they would not normally stimulate. Consequently, when these nerve endings receive a command for voluntary movement, the incorrectly connected nerves also induce an involuntary movement. Treatment modalities for this condition include surgery, facial retraining, Botox, facial expression therapy, and biofeedback.
The two most commonly studied cases of this condition are facial synkinesis and extraocular muscle synkinesis. Facial synkinesis is one of the more problematic sequelae of Bell’s palsy or idiopathic facial nerve palsy. Bell’s palsy results from compression of the facial nerve or cranial nerve VII. During the acute course of this disease, the facial nerve becomes nonfunctional, resulting in unilateral facial paralysis. Miswiring of nerves occurs as healing occurs, leading to synkinetic symptoms such as involuntary closing of the eyes when pouting or smiling, involuntary midface movement with intentional closing of the eyes, tightness of the neck with voluntary smiling, and watery eyes during the meal.
In extraocular muscle synkinesis, trauma to any two of cranial nerves III, IV, and VI leads to simultaneous voluntary and involuntary movements of six different extraocular muscles. Cranial nerve III or the oculomotor nerve innervates the medial rectus, inferior oblique, inferior rectus, and superior rectus. While cranial nerve IV, the trochlear nerve, innervates the superior oblique, cranial nerve VI, the abducens nerve, innervates the lateral rectus. In extraocular synkinesis involving the abducens and oculomotor nerves, when a person tries to look sideways using the affected eye, the eye looks toward the midline and the eyelid retracts. Other types involve the trigeminal nerve and the abducens nerve and the trigeminal nerve and the facial nerve.
The symptoms of synkinesia can be quite distressing, so many people see a doctor to seek permanent relief. Facial retraining is a conservative treatment modality that focuses on teaching how to actively control facial movements. Biofeedback therapy works in a similar way and the combination of biofeedback and facial retraining has synergistic effects. Botox, a reversible treatment involving the injection of botulinum toxin, has been shown to reduce facial hyperkinesia and hyperlacrimation.
Surgical modalities are rarely used and are reserved for patients who do not respond to the above conservative treatments. One such modality is called neurolysis, in which the involved nerve is destroyed. Neurolysis does not provide permanent relief, and symptoms often come back for worse. Another surgical modality is selective myotomy, in which a syncinetic muscle is removed. This provides more permanent relief than neurolysis, but has many complications including edema and bleeding.
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