The Natural Progression of Synkinesis.

Background: The severity of post paralysis facial synkinesis typically worsens after onset, but its progression over time is not well characterized. This study examines the time course of synkinesis progression.

Methods: Patients with a diagnosis of facial synkinesis presenting between 2010 and 2024 were assessed through photographic and videographic review using the eFACE Facial Nerve Clinician-Graded Scale. Patients included had at least two sets of standardized professional images and videos taken 3 or more months apart after facial palsy onset from any etiology. Patients who underwent surgical intervention for synkinesis or chemodenervation within the previous 3 months were excluded. The eFACE synkinesis score was assessed in 100-day increments after the onset of facial paralysis, with multivariable longitudinal analysis using generalized estimating equations (GEE).

Results: Of 409 synkinesis patients, 98 patients met inclusion criteria. Minimal symptoms were observed during the first 100 days following facial palsy onset. Synkinesis severity progressively increased, with the last period of statistically significant worsening occurring between 400 and 500 days. Synkinesis symptoms emerged as early as 1 month and as late as 10 to 11 months after facial palsy onset.

Conclusions: Synkinesis symptoms were minimal within 100 days of facial palsy onset and progressively worsened, with the greatest symptomatic worsening occurring between 200 and 300 days, before plateauing around 16 months, with no significant worsening thereafter. This study defines the timeline of post paralysis facial synkinesis, enabling evidence-based discussions of symptom progression.