Understanding clinical meaningfulness when targeting the depressor anguli oris muscle (DAO) with neuromodulators: a clinical prospective interventional study

Abstract

Background

Neuromodulator injections in the US increased by 24% from 2021 to 2022. This rise is attributed to new products and growing acceptance of minimally invasive aesthetic treatments. Recent studies emphasize the importance of facial anatomy for precision and, consequently, a higher efficacy of neuromodulator treatments. This study aims to evaluate the clinical efficacy of a novel previously proposed injection technique targeting the depressor anguli oris (DAO) muscle to improve oral commissure position. This clinical, prospective study included 34 volunteers from the Shinobu Clinic, São Paulo, Brazil. Patients received 3 units of onabotulinumtoxinA per side, injected mid-distance between the oral commissure and jawline, following the labiomandibular sulcus (LMS). Standardized photographs and assessments using the Oral Commissure Severity Scale (OCSS) and Global Aesthetic Improvement Scale (GAIS) were conducted before and 30 days post-treatment. Statistical analyses included t-tests, Wilcoxon Signed Rank test, and generalized linear models. The average increase in commissural height was 5.22% (p < 0.001). OCSS ratings improved significantly from baseline (clinician: 1.21 to 0.72, p < 0.001; patient: 0.93 to 0.69, p < 0.001). However, GAIS scores indicated no significant change (patient: 0.32, observer: 0.38; p = 0.491). The proposed injection technique improves perioral aesthetics objectively and subjectively. However, the lack of significant change in GAIS scores suggests that perceived improvements may not be clinically meaningful to patients. Future studies should focus on patient-centered evaluation methods to better assess aesthetic outcomes.