High-density Surface EMG Assessment of Motor Unit Alterations of the External Anal Sphincter Associated with Aging

摘要 肛门外括约肌（EAS）是维持粪便蠕动的关键，影响6%至19%。 65岁及以上的老年人居住在社区。年龄显著影响肛门直肠 在神经和肌源性方面都起作用。然而，有一个未满足的需要先进和较少- 有创方法定量和客观地评价EAS的神经肌肉功能。 肛门直肠成像技术与超声或磁共振成像提供有用的信息， 检测EAS中的解剖缺陷，但它们不能检测神经源性损伤。 肌内肌电图（EMG）是唯一可用于记录神经源性括约肌的技术 损伤，但其应用受到高度侵入性，可重复性差和无法描述的限制 全局神经支配阴部神经末梢运动潜伏期有几个局限性， 正常潜伏期并不排除神经病变，其临床意义仍有争议。肛肠 测压法测量肛门括约肌的压力、直肠的感觉和神经反射 正常排便所必需的食物然而，测量的各种参数的正常范围 是高度可变的并且可重复性差。 本项目的目标是开发一种微创EAS神经支配模式表征 一种使用高密度（HD）表面EMG记录和信号处理最新进展的技术 技术，定量和客观地评估EAS的神经肌肉功能，1）在休息时， 只有紧张性活动存在，2）在随意收缩期间，运动单位被选择性地募集， 3)当所有运动单位同时激活时，在超大阴部刺激下，以及 研究与衰老相关的EAS神经支配的具体变化。 这项研究代表了第一次努力定量和客观地表征神经支配 在三种不同的生理条件下的EAS模式。EAS的神经支配模式 其特征在于在休息时、在随意收缩期间和在超大阴部神经刺激下提供 与静息张力、自主激活和整体神经支配相关的特定EAS功能信息 分别为EAS。衰老对这三种情况下EAS神经支配的特异性变化的影响 将进行调查。建议EAS神经支配模式表征技术将作为一种新的 表型和预测工具的肛门直肠功能障碍所造成的神经源性弱点的EAS。的 结果将促进我们对肛门直肠神经肌肉功能障碍的病理生理学的理解 与衰老相关，也将对未来的治疗“选择”具有临床意义。 生物反馈或手术干预。

Abstract The external anal sphincter (EAS) is essential for maintaining fecal continence, which affects 6% to 19% of elderly individuals aged 65 years and older living in the community. Aging significantly affects anorectal function both neurogenically and myogenically. However, there is an unmet need of advanced and less- invasive approaches to quantitatively and objectively evaluate the neuromuscular function of the EAS. Anorectal imaging techniques with ultrasound or magnetic resonance imaging provide useful information in detecting anatomical defects in the EAS, but they are not capable of detecting neurogenic injuries. Intramuscular electromyography (EMG) is the only technique available for documenting neurogenic sphincter injury, but its application is limited by its highly invasive nature, poor repeatability and inability to describe global innervation. Pudendal nerve terminal motor latency has several limitations including the fact that a normal latency time does not exclude neuropathy and its clinical significance remains controversial. Anorectal manometry measures pressures of the anal sphincter muscles, sensation in the rectum, and neural reflexes that are necessary for normal bowel movements. However, normal ranges of various parameters measured are highly variable and poorly reproducible. The goal of this project is to develop a minimally invasive EAS innervation pattern characterization technique using the most recent advances in high-density (HD) surface EMG recording and signal processing techniques, to quantitatively and objectively assess the neuromuscular function of the EAS, 1) at rest when only tonic activities are present, 2) during voluntary contraction when motor units are selectively recruited, and 3) under supramaximal pudendal stimulation when all motor units are simultaneously activated, as well as to investigate specific alterations of the EAS innervation associated with aging. This research represents the first effort to quantitatively and objectively characterize the innervation patterns of the EAS under three different physiological conditions. The innervation patterns of the EAS characterized at rest, during voluntary contraction and under supramaximal pudendal nerve stimulation provide specific EAS function information associated with the resting tone, voluntary activation and global innervation of the EAS respectively. Aging effects on specific changes of the EAS innervation under these three conditions will be investigated. The proposed EAS innervation pattern characterization technique will serve as a novel phenotyping and predictive tool for anorectal dysfunctions caused by neurogenic weaknesses of the EAS. The results will advance our understanding of the pathophysiology of anorectal neuromuscular dysfunctions associated with aging, will also have clinical significance with regard to future therapeutic “choice” of biofeedback or surgical intervention.