What Is Synkinesis?
There is a group of motor neurological disorders called facial spasms, which include blepharospasm, hemifacial spasm, myokymia, and synkinesis. Each of these has its own diagnostic criteria and specific treatment.
Facial synkinesis is the involuntary contraction of facial muscles while carrying out another voluntary facial movement, such as smiling or closing the eyes.
When does synkinesis occur and why?
There are several causes of synkinesis and here we’ll discuss the most important ones.
Bell’s palsy
Also known as idiopathic facial palsy (IFP), this condition generally occurs after an abnormal regeneration of an injured facial nerve.
This paralysis is the most common and its cause is unknown. It’s suggested that it is due to the inadequate regeneration of the axons, resulting in the innervation of the incorrect muscles.
Other causes of facial paralysis include Ramsay-Hunt syndrome (due to herpes zoster), schwannoma, and arteriovenous malformations that compress the nerve in question.
Hemifacial spasm
This spasm is a disorder of the nerves that affect the muscles innervated by the seventh cranial nerve (facial nerve), resulting in involuntary, intermittent, and irregular contractions lasting seconds. These affect the orbicularis oculi muscle and, over the years, spread to the facial muscles on one side of the face.
They appear with stress, fatigue, and voluntary facial movements. They continue during sleep. They appear to occur by compression at the exit of the facial nerve root from the brainstem.
Marcus-Gunn syndrome
This is the congenital form of facial synkinesis. In this case, there’s an abnormal connection between the trigeminal nerve and the oculomotor nerve. As a consequence, when chewing, contractions occur in the upper eyelid, which usually droops.
How is synkinesis diagnosed?
Since the spasms may not appear during the consultation, the doctor takes a thorough medical history of the patient. After that, there will usually be an evaluation of the ears (otoscopy) and a complete neurological exam, including the cranial nerves. Facial function is analyzed at rest and with movements.
The most usual complementary studies are the following:
- Computed tomography of millimetric sections of the temporal bone without contrast.
- Gadolinium magnetic resonance imaging of the temporal bones and parotid gland to rule out vascular loops, compressions, or demyelinating causes.
- Electromyogram (EMG).
- Electroneuronography to evaluate nerve conduction in trauma cases.
- Hematology, erythrocyte sedimentation, CRP, rheumatoid factor.
Treatment of synkinesis
The ideal thing is to prevent the onset of synkinesis after a facial nerve injury in people with facial paralysis, through training. This consists of keeping the eyes open symmetrically while doing exercises with the mouth, 30 minutes a day, for a period of 10 months.
In cases of synkinesis, there are different possible approaches, among which are the following:
- Re-training with facial exercises, like the one already mentioned.
- Botulinum toxin injections.
- Combination of corneal care, re-training with facial exercises, and botulinum toxin.
- Surgery, reserved for cases whose results with botulinum toxin have been unsatisfactory. This includes neurectomy with facial nerve transfer and myomectomy of affected muscles.
In addition to treating spasms, dry eye should be addressed in the following way:
- Lubricating drops and ointment
- Temporary or permanent occlusion of the lacrimal point
- Surgery for correction of malpositions that favor dry eye
How to evaluate the evolution of synkinesis
The methodical evaluation of the clinical evolution of the patient allows you to obtain conclusions about the effects of the treatment. There are several scales created for these analyzes:
- Synkinesis Assessment Questionnaire (SAQ), which has been designed and validated for use in facial paralysis in order to assess the severity of symptoms and the impact on quality of life.
- Sunnybrook Facial Grading System, which provides facial symmetry score at rest and in motion, in addition to synkinesis.
- Electronic Clinician-graded Facial Function Scale (eFACE), which is a clinician-graded electronic facial function scale.
- Emotrics, which is software that uses an algorithm for the automated evaluation and measurement of facial movements.
Synkinesis doesn’t have to affect quality of life
Facial spasms, including synkinesis, have psychosocial implications in patients. About a quarter of people with facial paralysis may have synkinesis.
Today good results are obtained with botulinum toxin treatment and facial surgery. These results can be periodically evaluated by clinicians using scales and novel imaging methods.
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