Predictors of Facial Synkinesis Severity

We read with interest the July of 2025 article by Rail et al. entitled “Predictors of Facial Synkinesis Severity,”1 and we congratulate the authors on their thought-provoking study. This retrospective cohort study of 249 synkinesis patients represents the first large clinical series to investigate potential predictors of facial synkinesis severity, which include age of facial palsy onset older than 50 years, diabetes, smoking, and intratemporal facial nerve injury. For idiopathic or infectious cases of facial palsy, onset during pregnancy was associated with more severe synkinesis. The pathophysiology of synkinesis remains poorly understood but has typically been attributed to misdirected regenerating axons and polyneuronal innervation, with “too much” motor recovery in the “wrong places.” Thus, it is interesting that the factors identified by the authors, which are known to be associated with poor neuromuscular recovery following peripheral nerve injury, are also associated with more severe synkinesis. These include age, where there is a decline in the rate of axonal regeneration as well as reduced cortical plasticity; diabetes and smoking, which are both associated with microvascular disease and neural ischemia; and pregnancy, during which patients have increased fluid retention and may be more susceptible to compression neuropathy.2,3,4 The association of intratemporal versus extratemporal lesions with synkinesis is consistent with axonal misdirection. Unlike the distinct branched topography of the extratemporal facial nerve, the intratemporal facial nerve has a densely organized intraneural topography, where regenerating axons may be more likely to be misdirected down adjacent pathways leading to anatomically distant neuromuscular junctions in the face.5,6 Despite the interesting findings, the study has several limitations. Although the eFACE provides a comprehensive assessment of facial palsy and synkinesis, the measure was originally described and validated using video recordings; in the present study, photographs were used.7 As synkinesis is a dynamic phenomenon, it would be valuable to know exactly which specific facial expression photographs were assessed in this study and how patients were instructed to demonstrate these facial expressions. Furthermore, the eFACE grades synkinesis based on the movement that provides the most severe synkinesis; however, this is not always what causes the patient the most distress. This is particularly important, as the ultimate goal of synkinesis treatment is to address the patient’s concerns and improve the function that is most distressing to them. It is important to focus on which particular expressions or facial movements subjectively cause patients with synkinesis the most distress and endeavor to most effectively address these specific movements with neuromodulator injections or selective neurectomies, rather than only achieving improved symmetry at rest or when smiling. Finally, the study does not investigate whether the identified risk factors have an impact on the outcomes of synkinesis surgery, such as improvement in symptoms or symmetry, and recurrence of symptoms. Synkinesis is a debilitating sequelae of facial nerve palsy and remains poorly understood and treated. We congratulate Rail et al. on their excellent study that furthers our understanding of synkinesis and also generates many new questions to be investigated. DISCLOSURE The authors have no relevant financial disclosures to report.