咀嚼筋障害におけるボツリヌス毒素注射の筋電活動および咬合力への影響．無作為化臨床試験

Effect of Botulinum Toxin Injection on EMG Activity and Bite Force in Masticatory Muscle Disorder: A Randomized Clinical Trial.

抄録

A型ボツリヌス毒素（BoNT-A）は、咀嚼筋痛障害の治療に用いられることが多くなっているが、安全な投与量や再注入間隔を確立する必要がある。この無作為化臨床試験の目的は，咀嚼筋のパフォーマンスの障害の程度と期間を評価することであった．57名の被験者を無作為に2群に分け、一方にはBoNT-Aを先に投与し（＝28名）、他方には生理食塩水を先に投与した（＝29名）、16週目にクロスオーバーし、合計32週間のフォローアップを行った。合計50UのBoNT-Aを咬筋と側頭筋に両側から注射した。筋電図（EMG）活動および咬合力を評価した。18週目まで有意な筋電活動の低下が認められ（≦001），33週目には完全に回復した．最大咬合力は11週目まで有意に低下し（≦005），25週目に全回復した．以上より、咀嚼筋痛症にBoNT-A 50Uを投与した場合、再注入間隔は33週までに筋機能が回復するため、安全であると考えられる。

Botulinum toxin type A (BoNT-A) is increasingly used in treating masticatory muscle pain disorder; however, safe doses and reinjection intervals still need to be established. The purpose of this randomized clinical trial was to evaluate the degree and duration of the impairment of masticatory muscle performance. Fifty-seven subjects were randomly divided into two groups: one of which received BoNT-A first ( = 28) while the other received saline first ( = 29), with the cross-over being in week 16, and a total follow-up period of 32 weeks. A total dose of 50 U of BoNT-A was injected in the masseter and temporal muscles bilaterally. Electromyographic (EMG) activity and bite forces were assessed. A significant reduction in EMG activity was observed up to week 18 ( ≤ 001), with total recovery at week 33. A significant reduction in maximum bite force was observed up to week 11 ( ≤ 005), with total recovery at week 25. In conclusion, when treating masticatory muscle pain disorder with 50 U of BoNT-A, a reinjection interval of 33 weeks can be considered safe since the recovery of muscle function occurs by that time.