# A Novel Injection Technique to Prevent Exacerbation of Sunken Cheek After Botulinum Toxin Type A Treatment for Masseter Hypertrophy: A Prospective Clinical Study

## TL;DR

A new injection technique for treating masseter hypertrophy with botulinum toxin helps prevent or reduce sunken cheeks, a common side effect.

## Contribution

A novel injection technique for botulinum toxin type A is introduced to prevent exacerbation of sunken cheeks after treatment.

## Key findings

- The novel injection technique did not worsen sunken cheeks in any participants during follow-up.
- Some participants showed improvement in cheek depression severity after treatment.
- Adverse effects were temporary and occurred mainly within the first two weeks.

## Abstract

Sunken cheek is often an undesirable aesthetic outcome, making the face appear gaunt and tired. It is also a common adverse effect of injections for treating masseter hypertrophy. This study aims to assess the efficacy of a novel injection technique in preventing sunken cheek after botulinum toxin type A (BoNT‐A) treatment for masseter hypertrophy, focusing on minimizing adverse aesthetic effects while ensuring effective masseter muscle reduction.

The degree of sunken cheek was compared on both sides before injection and 4 weeks postinjection using the validated assessment scales for the midface by Jean Carruthers, etc. Telephone follow‐ups were conducted in weeks 1, 2, and 4 to assess subjective perceptions of sunken cheek, monitor adverse effects, and evaluate participant satisfaction with the procedure and the hospital.

Before treatment, there were nine participants with Grade 0, 62 with Grade 1, and 11 with Grade 2 sunken cheek. At week 4, the numbers were 13 with Grade 0, 59 with Grade 1, and 10 with Grade 2. No patients reported an aggravation of sunken cheek during follow‐up calls. Adverse reactions primarily occurred within the first 2 weeks and improved spontaneously.

The novel BoNT‐A injection technique for masseter hypertrophy is safe and prevents the exacerbation of sunken cheeks. The results suggest that this method does not aggravate sunken cheeks and may even improve cheek depression severity in some individuals.