Effect of botulinum toxin on endplate noise in myofascial trigger spots of rabbit skeletal muscle.

Objective: To assess the effect of botulinum toxin type A (BTX-A) on the endplate noise prevalence in rabbit myofascial trigger spots to confirm the role of excessive acetylcholine release on the pathogenesis of myofascial trigger points and to develop an objective indicator of the effectiveness of BTX-A in the treatment of myofascial trigger points.

Design: Eighteen adult New Zealand rabbits were divided into three groups that received a single bolus of BTX-A over a myofascial trigger spot region on one side of the biceps femoris muscle. Another 10 rabbits received multiple-point injections in a myofascial trigger spot where endplate noises were found. A control study was performed on the other side of the biceps femoris muscle. The endplate noise prevalence in a myofascial trigger spot region was assessed.

Results: It was found that injection of BTX-A reduced the prevalence of endplate noise. No significant differences between a single bolus injection and multiple-point injections were noted, although there was some evidence that multiple-point injections might maintain the endplate noise decreasing effect much longer than a single injection.

Conclusions: This study demonstrated the suppressive effect of BTX-A on endplate noise prevalence in a myofascial trigger spot region. The prevalence of endplate noise in the myofascial trigger point region may be a useful objective indicator for evaluating the therapeutic effectiveness of BTX-A injection to treat myofascial trigger points.