Masseter muscle hypertrophy occurs as a soft enlargement of the jaw muscles near the angle of the lower jaw and seldom presents a major health problem. However, in some individuals the swelling can be associated with pain or may be so large that it causes facial disfigurement. Although the cause of the condition is unclear it does appear to be more common in certain ethnic groups.
Symptoms such as pain can be treated with muscle relaxants and may also include bite adjustments or involve the use of splints on the teeth. Surgical reduction of the jaw muscle or injections of botulinum toxin type A directly into the muscle are other treatment options.
Although the use of botulinum toxin injections might appear to have certain advantages over surgery the authors in this review did not find any high quality studies evaluating the effectiveness and potential harms of botulinum toxin type A in the management of benign masseter hypertrophy. The authors concluded that future research should aim to provide evidence for people to make informed decisions about whether botulinum toxin type A is effective and that further randomized controlled trials should be well designed and reported according to the ‘Consolidated Standards of Reporting Trials (CONSORT)’ statement (http://www.consort-statement.org).