Long-term therapy with botulinum toxin in facial synkinesis: Retrospective data analysis of data from 1998 to 2018.

[OBJECTIVES] Treatment with botulinum toxin A (BoNT) is the therapy of choice for many patients with facial synkinesis. Repeated injections relieve hypertonicity and hyperkinesis of reinnervated mimic muscles. Aim of the study was to prove if the injection regime and dosage of BoNT change during long-time therapy.

[DESIGN] Retrospective analysis of patients´ data, who were treated for synkinesis with BoNT from 1998 to 2018.

[SETTING] Tertiary referral facial nerve centre.

[PARTICIPANTS] Injection pattern of BoNT was based on clinical symptoms, observations of the specialist and on previous treatment pattern. Onabotulinumtoxin (OnaBoNT), Incobotulinumtoxin (IncoBoNT) and Abobotulinumtoxin (AboBoNT) were available for treatment. Patients consulted our department for following treatment as soon as the symptoms re-occurred.

[MAIN OUTCOME MEASURES] Change in dosage and injection pattern, the time intervals between treatments over the entire therapy period.

[RESULTS] Seventy-three patients were repeatedly injected. The median number of treatments was 18, the median treatment interval was 3.0 months. During the initial treatment, orbicularis oculi and the mentalis muscles were the most frequently injected muscles (94%). During repeated treatment, the number of injected muscles increased significantly (P < .0001), whereas the dose per muscle remained stable. The initial dose was 24 U (95%-CI 22-27 U) for OnaBoNT and IncoBoNT; 69 U for AboBoNT(95%-CI 44-94 U). We observed a significant increase in dosage for OnaBoNT and IncoBoNT (P < .0001) during the long-term therapy. The time intervals between treatments were stable for all three BoNT preparations (P > .05).

[CONCLUSIONS] We observed significant change in treatment dose and injection pattern of BoNT in patients with facial synkinesis. These results provide an orientation in dose finding and injection regimen of BoNT in the long-term course of therapy.