Effects of botulinum toxin type A on the masseter muscles of a patient with a temporomandibular joint disorder of muscular origin: A case report

Temporomandibular joint disorders (TMDs) typically manifest with symptoms and signs such as pain, mandibular movement, dysfunction, or joint sounds. Botulinum toxin type A (BTX/A) is a biological toxin that inhibits the release of the neurotransmitter acetylcholine at the neuromuscular junction. This toxin is used to treat hyperactivity of masseter muscles and TMD symptoms. This case report aimed to investigate the effects of BTX/A injection in the masseter and lateral pterygoid muscles of a patient with painful symptoms of TMDs via electromyography (EMG), with a follow-up of six months post-treatment. During each visit, the clinical effects, which were evaluated based on pain intensity (NPRS), the bruxism questionnaire, and maximum mouth opening, were evaluated at five-time points, pre-injection and 2, 6, 12, and 24 weeks after the injection. Based on this case report, there was a clear improvement in the studied parameters, with a significant decrease in the electromagnetic activity of the injected muscles as shown by EMG; thus, BTX/A can be considered an effective treatment to relieve symptoms and improve the quality of life in patients with TMDs of muscular origin, relying on EMG as an effective diagnostic tool and for subsequent evaluation of treatment results. • Use of electromyography for accurate diagnosis of muscular temporomandibular joint disorders. • How to inject botulinum toxin into the lateral pterygoid muscle. • The use of botulinum toxin as an effective treatment for bruxism and muscular TMJ disorders.