[Synkinesis in facial palsy: What do we know about the physiopathology?]

Synkinesis is a disabling sequelae of facial palsy, which worsens facial asymmetry and diminishes the patients' quality of life. Their physiopathology is partially known, but cannot explain all the synkinesis.

We report a literature review of the state of the art concerning the knowledge on synkinesis physiopathology, as well as their management.

It is accepted that the physiopathological mechanism of synkinesis is mixed. The phenomena of cerebral plasticity, aberrant nerve regrowth, hyperexcitability of the facial nerve nucleus and ephaptic nerve transmission, have been observed. We propose a new physiopathological hypothesis: synkinesis could be the consequence of latent circuits activation, preexisting in the healthy subject. We could propose three potential latent circuits: physiological synergistic contractions, adjacent motor units recruitment, and reactivation of remote latent circuits for function compensation. The treatment options are multiple, dominated by chemodenervation, whose effectiveness is undeniable. Rehabilitation has also proven its effectiveness, particularly with feedback techniques. Finally, surgery helps with these options. However, the indications of the different treatments remain to be codified.

The validation of our physiopathological hypothesis would allow a better understanding and a better screening of synkinesis, in order to propose a more adapted treatment.