516 - Muscle Selection Matters: A Case of Bruxism Relief with Pterygoid Botulinum Toxin Injections

Initial treatment targeted the masseter muscles with 10 units of onabotulinumtoxinA bilaterally. The patient reported partial improvement. At a follow-up session, the dose to the right masseter was increased to 15 units, while the left remained at 10 units. This adjustment did not provide further relief and led to right-sided chewing weakness.

The injection plan was then modified to target the pterygoid muscles instead, with 10 units administered bilaterally. This change resulted in significant relief from nocturnal bruxism without functional compromise, marking the most effective response to date.

Discussions: Masseter and temporalis muscles are the most commonly injected targets for bruxism. However, the pterygoid muscles also contribute significantly. The medial pterygoid muscle fibers run in the same direction as the masseter muscle, assisting with jaw elevation, while the lateral pterygoid muscle facilitates grinding movements through its role in mediolateral mandibular translation. Due to these anatomical and functional parallels, injecting the pterygoids may reduce bruxism-related activity. In this case, pterygoid injection yielded better outcomes than masseter injection alone. While they were used as an alternative here, both muscle groups may be injected together for comprehensive management.

Conclusions: This case highlights the importance of individualized muscle selection in botulinum toxin treatment. Targeting the pterygoid muscles provided improved bruxism relief with fewer side effects, supporting their use in cases refractory to traditional masseter injections.