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.