Efficacy and Safety of Incobotulinumtoxin-A for Trapezius Muscle Reduction: Quantitative Evaluation With Imaging Studies.

Background: Bilateral trapezius muscle hypertrophy can cause both aesthetic concerns and physical discomfort. This study aimed to objectively assess the clinical efficacy and safety of incobotulinumtoxin-A (INCO) injections in patients with bilateral trapezius muscle hypertrophy.

Methods: This single-center retrospective study included 22 patients with bilateral trapezius muscle hypertrophy who received INCO injections and were followed up at 1, 3, and 6 months after treatment. Evaluation methods included clinical photography, imaging analysis with ultrasound and 3-dimensional computed tomography, and the Global Aesthetic Improvement Scale.

Results: Photographic evaluations revealed significant reductions in surface area at 1 month (28.82% ± 3.93%), 3 months (26.83% ± 3.60%), and 6 months (28.74% ± 3.30%), compared with baseline (all P < 0.001). Ultrasonography showed significant reductions in thickness at 1 month (5.20 ± 1.01 mm) and 3 months (4.64 ± 0.80 mm), which were sustained until 6 months (5.23 ± 0.89 mm), compared with baseline (P < 0.001). A notable volume reduction in the upper trapezius muscle was detected in the 3-dimensional computed tomography scan of a single patient. The Global Aesthetic Improvement Scale scores indicated high satisfaction, with no significant adverse events.

Conclusions: INCO injections effectively reduced trapezius muscle size, with sustained results up to 6 months posttreatment. This study supports the use of INCO as a safe and effective option for managing trapezius hypertrophy.