Compensatory Masseteric Bulging: A Novel Observation and Its Implications for Botulinum Neurotoxin Injection...

Area of Science:

• Aesthetic Medicine
• Facial Anatomy
• Neuromodulator Therapy

Background:

• Compensatory masseteric bulging is a novel complication from botulinum neurotoxin (BoNT) injections targeting the lower masseter.
• This hypertrophy of upper masseteric layers occurs due to compensatory mechanisms for weakened lower regions, leading to facial asymmetry.
• Conventional injection methods often neglect the masseter's three-layered anatomy (superficial, middle, deep), increasing the risk of asymmetry.

Purpose of the Study:

• To introduce a novel retrograde, layered injection technique for BoNT administration in the masseter muscle.
• To prevent compensatory masseteric bulging and improve facial symmetry.
• To highlight the importance of anatomical precision and tailored dosing in masseter hypertrophy management.

Main Methods:

• A retrograde, layered injection approach is proposed, ensuring even distribution of BoNT across all masseteric layers.
• Ultrasound guidance is utilized for precise toxin delivery, targeting specific muscle layers and avoiding adjacent structures.
• Personalized dosing strategies are implemented, considering individual muscle thickness, activity, and prior treatment history to prevent over-atrophy.

Main Results:

• A case study of a 34-year-old female demonstrated upper masseter hypertrophy (12 mm) after sequential lower masseter BoNT treatments.
• Ultrasound imaging confirmed hypertrophy in the upper layer and atrophy in the lower layer.
• Treatment with 50 units of LetibotulinumtoxinA via the layered technique reduced upper masseter thickness to 8 mm, successfully restoring facial symmetry.

Conclusions:

• Compensatory bulging necessitates a comprehensive treatment approach that addresses the entire masseter muscle.
• Layered injections, enhanced by ultrasound guidance and personalized dosing, effectively mitigate the risk of facial asymmetry.
• Clinicians should integrate detailed anatomical knowledge and advanced imaging for optimal outcomes in managing masseter hypertrophy.