Related Experiment Video
Updated: Jan 9, 2026
Rodent Model of Masseter Volumetric Muscle Loss for Studying Bioengineering Materials
Published on: May 31, 2024
Longitudinal Assessment of Masseter Muscle Elasticity Changes After BoNT-A Injection Using Ultrasound Elastography: A
Mengyue Yan1, Yuna Luo1, Qian Wu2
1Department of Craniomaxillofacial Surgery, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, CAMS & PUMC 33 Badachu Road Shijingshan District, Beijing, 100144, People's Republic of China.
Background:
Botulinum neurotoxin type A (BoNT-A) is widely used to treat masseter hypertrophy, but its long-term structural effects remain unclear. While animal studies suggest reversible and irreversible remodeling, human data on microstructural changes are limited. Ultrasound elastography (USE) offers a non-invasive method to quantitatively assess muscle elasticity and detect fibrosis risk.
Methods:
A prospective self-controlled trial enrolled 14 subjects (28 masseter muscles) aged 21-27 years. Masseter thickness and standardized USE measurements (shear wave velocity, V median) were performed at baseline and 1, 3, and 6 months post-injection. Statistical analysis included paired t-tests and Spearman correlation.
Results:
Masseter thickness decreased significantly by 28.9-31.5% at 1-3 months (p ≤ 0.05), with partial recovery (47.4%) by 6 months. V median (elasticity) declined at 1-3 months (2.53 ± 0.46 m/s to 2.10 ± 0.45 m/s, p ≤ 0.05), but returned to baseline by 6 months (2.70 ± 0.68 m/s, p > 0.05), indicating reversible structural adaptation. Thickness and elasticity changes were uncorrelated, suggesting distinct recovery mechanism.
Conclusion:
BoNT-A induces transient masseter atrophy and elasticity reduction, with full elastic recovery by 6 months despite incomplete volume restoration. USE effectively tracks reversible microstructural remodeling, distinguishing atrophy from fibrosis. These findings support USE as a tool for optimizing injection timing and monitoring functional recovery.
Level Of Evidence Ii:
This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .
