Upper Motorneuron Spasticity Research Program, West Park Healthcare Centre, Toronto, ON M6M 2J5, Canada.
Neurosci Lett. 2013 Apr 29;541:20-3. doi: 10.1016/j.neulet.2013.02.025. Epub 2013 Feb 28.
Botulinum toxin, frequently used to manage focal limb spasticity, has been reported to affect both extrafusal and intrafusal fibers of the injected muscle. Since most studies have used spinal reflexes, it is difficult to isolate the intrafusal effects from extrafusal and central effects. In a paper by On et al. [7], both stretch and H-reflexes were used to examine the intrafusal effects of botulinum toxin injections. Revisiting the data from On et al. [7] presented a unique opportunity to describe a novel method of measuring the effect of botulinum toxin-A on muscle spindle activity in patients with spasticity. H-reflex, maximum M-wave, and Achilles tendon reflex were serially assessed in ten patients with stroke pre-, 2, 4, and 12 weeks post-botulinum. In order to assess the intrafusal effects, we subtracted the %change in H-reflex amplitude from baseline (representing extrafusal and central effects) from the %change in Achilles tendon reflex amplitude from baseline (representing intrafusal, extrafusal and central effects). Using this formula, our results suggest that botulinum induces significant chemodenervation of the intrafusal muscle fibers (33% decreases). Intrafusal effects were greatest at 2 weeks, but tapered off by 12 weeks post-botulinum (p<0.017). We found a significant positive correlation between the intrafusal effects of botulinum toxin and changes in modified Ashworth scale. Our method of assessing the effects of botulinum toxin shows significant effect on intrafusal fibers, which correlates with clinical manifestation of spasticity. Future studies need to investigate ways to maximize intrafusal effects and minimize extrafusal effects of botulinum therapy.
肉毒毒素常用于治疗局部肢体痉挛，据报道其可影响注射肌肉的梭外和梭内纤维。由于大多数研究都使用脊髓反射，因此很难将梭内效应与梭外和中枢效应分开。在 On 等人的一篇论文中，[7]同时使用拉伸和 H 反射来检查肉毒毒素注射对梭内效应的影响。重新审视 On 等人的数据，[7]提供了一个独特的机会来描述一种测量肉毒毒素-A 对痉挛患者肌梭活动影响的新方法。在接受肉毒毒素治疗前、2、4 和 12 周后，连续评估了 10 例脑卒中患者的 H 反射、最大 M 波和跟腱反射。为了评估梭内效应，我们从基线（代表梭外和中枢效应）中减去 H 反射幅度的百分比变化，从基线（代表梭内、梭外和中枢效应）中减去跟腱反射幅度的百分比变化。使用这个公式，我们的结果表明肉毒毒素可显著地去神经支配梭内肌纤维（减少 33%）。梭内效应在 2 周时最大，但在肉毒毒素治疗后 12 周时逐渐减弱（p<0.017）。我们发现肉毒毒素的梭内效应与改良 Ashworth 量表的变化之间存在显著的正相关。我们评估肉毒毒素作用的方法显示出对梭内纤维的显著影响，这与痉挛的临床表现相关。未来的研究需要探讨如何最大化肉毒毒素治疗的梭内效应并最小化梭外效应。
