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Botulinum toxin for masseter hypertrophy

  • Review
  • Intervention




Benign masseter muscle hypertrophy is an uncommon clinical phenomenon of uncertain aetiology which is characterised by a soft swelling near the angle of the mandible. The swelling may on occasion be associated with facial pain and can be prominent enough to be considered cosmetically disfiguring. Varying degrees of success have been reported for some of the treatment options for masseter hypertrophy, which range from simple pharmacotherapy to more invasive surgical reduction. Injection of botulinum toxin type A into the masseter muscle is generally considered a less invasive modality and has been advocated for cosmetic sculpting of the lower face. Botulinum toxin type A is a powerful neurotoxin which is produced by the anaerobic organism Clostridium botulinum and when injected into a muscle causes interference with the neurotransmitter mechanism producing selective paralysis and subsequent atrophy of the muscle.


To assess the effects of botulinum toxin type A in the management of benign bilateral masseter hypertrophy.

Search methods

We searched the following databases in August 2008: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 3); MEDLINE (via PubMed) (1950 to August 2008); EMBASE (via (1980 to August 2008); and LILACS via BIREME. We searched two bibliographic databases of regional journals which may be expected to contain relevant trials (IndMED and Iranmedex) using free text terms appropriate for this review.

Selection criteria

Randomised controlled clinical trials (RCTs) and controlled clinical trials (CCTs) comparing intra-masseteric injections of botulinum toxin versus placebo administered for cosmetic facial sculpting in individuals of any age with bilateral benign masseter hypertrophy, which had been self-evaluated and confirmed by clinical and radiological examination. We excluded participants with unilateral or compensatory contralateral masseter hypertrophy resulting from head and neck radiotherapy.

Data collection and analysis

Two review authors conducted screening of studies in duplicate and independently, and although no eligible trials were identified, the two authors had planned to extract data independently and assess trial quality using standard Cochrane Collaboration methodologies.

Main results

We retrieved 167 references to studies, none of which matched the inclusion criteria for this review and all of which were excluded.

Authors' conclusions

We were unable to identify any randomised controlled trials on the efficacy of intra-masseteric injections of botulinum toxin for people with bilateral benign masseter hypertrophy. The absence of high level evidence for the effectiveness of this intervention emphasises the need for well-designed, adequately powered, randomised controlled clinical trials (RCTs) and controlled clinical trials (CCTs).








我們於2008年8月搜尋下列資料庫:the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008年 issue 3); MEDLINE (via PubMed) (1950年至2008年8月); EMBASE (via (1980年至2008年8月); LILACS via BIREME.我們預期兩個區域性期刊的參考書目資料庫包含相關試驗,並且予以檢索(IndMED and Iranmedex),使用適於本篇研究的內文。




兩位作者分別篩選資料並重複確認。儘管未找到符合的資料,仍然分別提取數據並使用Cochrane Collaboration methodologies評估試驗品質。







此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。


A型肉毒桿菌毒素之於良性雙側咀嚼肌肥大:咀嚼肌肥大見於下頜角附近的肌肉變得柔軟增大,少有嚴重的健康問題。然而有些患者可能伴隨臉部疼痛或是因太肥厚造成臉部不美觀。儘管原因不明,在某些族群卻很常見。諸如疼痛等症狀可以用肌肉鬆弛劑治療,或是使用牙齒副木,或者調整咬合方式。也可以使用外科手術以減量下頜肌肉或是注射A型肉毒桿菌毒素至肌肉的方式。 儘管注射肉毒桿菌毒素似乎優於外科治療,然而關於A型肉毒桿菌毒素用於良性咀嚼肌肥厚的效果和可能的傷害,卻並沒有找到任何品質較佳的研究。未來的研究必須能夠提供證據顯示肉毒桿菌毒素是否有效,且未來必須根據Consolidated Standards of Reporting Trials(CONSORT)設計良好的的隨機對照試驗。

Plain language summary

Botulinum toxin type A for benign bilateral masseter hypertrophy

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 (  

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