A Randomized, Double-Blind, Controlled Study Evaluating the Efficacy of Botulinum Toxin Type A (Hengli) Injection for LowerLip Asymmetry in Children With Craniofacial Microsomia
This study focuses on children with hemifacial microsomia (HFM), a common congenital craniofacial deformity caused by abnormal development of the first and second branchial arches. Up to 45% of children with HFM have facial nerve dysplasia, most frequently involving the mandibular marginal branch. These children present with asymmetric lower-lip movement called crooked-mouth smile during smiling, speaking or crying. Unlike asymmetric crying syndrome, this condition does not resolve spontaneously and may gradually get worse. Crooked-mouth smile results from muscle weakness of the lower lip on the affected side, leading to dynamic perioral muscle imbalance. Static treatment includes botulinum toxin injection, muscle resection, nerve cutting and fascia suspension; dynamic treatment includes muscle transfer procedures. Early intervention is important for children's psychological well-being. Botulinum toxin injection is minimally invasive, safe and reversible, and is regarded as a preferred initial therapy. However, prospective clinical evidence regarding its efficacy, safety and appropriate dosage in this pediatric population remains insufficient. This prospective study aims to explore the safety, effectiveness and optimal dose of botulinum toxin injection for treating crooked-mouth smile in children with HFM and mandibular marginal branch dysplasia.
• Children under 18 years old diagnosed with hemifacial microsomia (HFM) and lower-lip asymmetry, with congenital injury of the marginal mandibular branch of the facial nerve, presenting with lower-lip movement disorder and lower-lip asymmetry during smiling and teeth-baring.
• Subjects who are able to comply with study protocols and visit schedules.
• Subjects whose guardians provide voluntary written informed consent.