Identifying the Neuromuscular Origins of Hand Muscle Weakness in Children with Hemiplegic Cerebral Palsy

项目总结 脑性瘫痪是最常见的儿童运动障碍。最常见的亚型是脑性偏瘫 瘫痪(Hcp)，特征是身体一侧的感觉运动障碍，尤其是上半身。 四肢。上肢感觉运动控制受损会对教育机会产生负面影响， 参与日常活动、未来的工作前景和自尊。因此，上肢，尤其是上肢 手，是职业和物理治疗的重要目标。尽管做出了这些努力，但实质性的功能 上肢的缺陷通常会持续到成年，并导致终生缺陷。的主要贡献者 损害是一种严重的弱点。儿童的相对力量缺陷随着年龄的增长而增加，并延伸到 成人期。不幸的是，这种疲软的潜在生理原因还没有得到很好的理解。可能的 导致CP肌肉无力的因素包括自愿兴奋肌肉的能力减弱，过度 拮抗剂的共同激活，并改变了肌肉形态。这项研究的目的是确定相对的 这些损害机制对观察到的HCP儿童的虚弱有贡献。 每个参与者都将被要求完成一系列实验。在第一个实验中，可能是非自愿的 手部肌肉过度兴奋，表现为痉挛、过度协同激活或延迟松弛 时间，将被评估。为了量化痉挛，定制的伺服控制夹具将施加受控的伸展 通过旋转掌指(MCP)关节定位手指肌肉。痉挛反射反应 将根据阻力扭矩和手指肌肉的激活来量化，如表面测量 肌电(EMG)。共激活和松弛时间将从记录的肌电信号中测量 当手固定在夹具内时，关于MCP关节的自动等距扭矩生成。等速运动 还将对收缩进行评估，以评估电力短缺。对于第二个实验，可能存在的赤字 关键的外在手指肌肉的自愿激活将通过抽动插补和中央 激活率技术。表面电刺激将叠加在自发激活的 指定手指肌肉以产生最大等长指力。偏瘫手的激活值将 与非轻瘫手和典型发育儿童的测量值进行比较。这些 实验数据将被用于开发特定于受试者的手的神经机械计算机模型 OpenSim。肌肉形态，如长度和横截面积，将用超声波测量，以 包含在每个定制型号中。将使用计算机模型来确定指尖的敏感度 力量和控制不同的损伤机制。总而言之，这项研究的结果将有助于更好地 告知脑瘫儿童目前和未来的康复技术。

PROJECT SUMMARY Cerebral palsy is the most common pediatric motor disorder. The most prevalent subtype, hemiplegic cerebral palsy (HCP), is characterized by sensorimotor dysfunction on one side of the body, especially affecting the upper limb. The impaired sensorimotor control of the upper limb can negatively impact educational opportunities, participation in daily activities, future job prospects, and self-esteem. For this reason, the upper limb, particularly the hand, is a significant target for occupational and physical therapy. Despite these efforts, substantial functional deficits in the upper limb often persist into adulthood and contribute to lifelong limitations. A main contributor to impairment is profound weakness. The relative strength deficits increase with age in children and extend into adulthood. Unfortunately, the underlying physiological causes of this weakness are not well understood. Possible contributors to muscle weakness in CP include a diminished ability to voluntarily excite the muscles, excessive co-activation of antagonists, and altered muscle morphology. The goal of this research is to determine the relative contributions of these impairment mechanisms to observed weakness in children with HCP. Each participant will be asked to complete a set of experiments. In the first experiment, possible involuntary hyperexcitability of hand muscles, as manifested as spasticity, excessive coactivation, or delayed relaxation time, will be assessed. To quantify spasticity, a custom servo-controlled jig will impose controlled stretch of the targeted finger muscles through rotation of the metacarpophalangeal (MCP) joints. The spastic reflex response will be quantified in terms of resistance torque and activation of finger muscles, as measured with surface electromyography (EMG). Coactivation and relaxation time will be measured from EMG signals recorded during voluntary isometric torque generation about the MCP joints with the hand fixed within the jig. Isokinetic contractions will also be assessed to evaluate deficits in power. For the second experiment, possible deficits in voluntary activation of key extrinsic finger muscles will be examined through twitch interpolation and central activation ratio techniques. Surface electrical stimulation will be superimposed on the voluntary activation of specified finger muscles to produce maximum isometric finger force. Activation values for the paretic hand will be compared with those of the non-paretic hand and the values measured in typically developing children. These experimental data will be used to develop subject-specific neuromechanical computer models of the hand in OpenSim. Muscle morphology, such as length and cross-sectional area, will be measured with ultrasound for inclusion in each custom model. The computer models will be used to determine the sensitivity of fingertip strength and control to different impairment mechanisms. Together, the results of this study will help to better inform current and future rehabilitation techniques in children with cerebral palsy.