Use of botulinum toxin type A in nonconventional regions of the mid and lower face, and neck: a systematic review of clinical trials

Botulinum toxin type A (BoNT-A) has expanded its indications beyond the upper facial third toward less conventional anatomical regions of the mid and lower face and neck, including the mandibular, cervical, and nasal areas, with both aesthetic and functional objectives. However, the available evidence remains scattered and demonstrates considerable variability regarding injection techniques, dosing protocols, and evaluated outcomes. The aim of this systematic review was to evaluate the efficacy and safety of BoNT-A use in these regions through a critical analysis of the literature. A systematic search was conducted in biomedical databases, including clinical trials assessing the application of botulinum toxin in nontraditional areas of the mid and lower face and neck. A total of 18 studies involving 2106 participants were included. Variables analyzed included clinical indications, administered doses, injection techniques, duration of therapeutic effect, and adverse events. The results demonstrated clinically significant improvement across several aesthetic and functional indications, particularly reduction of masseter volume, improvement of platysmal bands, and control of nasal symptoms. Reported adverse events were predominantly mild and transient. In conclusion, BoNT-A represents an effective and safe therapeutic alternative for the treatment of less conventional regions of the face and neck. Nevertheless, the heterogeneity identified highlights the need for standardized protocols and studies with greater methodological rigor and long-term follow-up.