Duque Julie, Thonnard Jean-Louis, Vandermeeren Yves, Sébire Guillaume, Cosnard Guy, Olivier Etienne
Laboratory of Neurophysiology, School of Medicine, Université catholique de Louvain, Brussels, Belgium.
Brain. 2003 Mar;126(Pt 3):732-47. doi: 10.1093/brain/awg069.
One of the most devastating consequences of early corticospinal lesions is the impaired dexterity that results in a noticeable deficit while manipulating small objects. One purpose of the present study was to investigate the extent to which a deficit in the coordination of fingertip forces when grasping and lifting an object between the thumb and index finger could account for the impaired dexterity in patients with congenital hemiplegia (CH). A second objective was to examine whether, in these patients, deficits in skilled hand movements are correlated with the importance of structural damage to the corticospinal tract. The scaling and coordination of fingertip forces during precision grip was investigated in 16 CH patients (aged 8-19 years) and 16 age- and sex-matched control subjects. Proprioception, stereognosis, pressure sensitivity and motor upper limb function (including digital and manual dexterity) were also assessed quantitatively. The structural damage of the corticospinal tract was estimated by measuring the cross-sectional area of cerebral peduncles with MRI and by calculating an index of symmetry between the two peduncles. In CH patients, a large number of parameters measured during the grip-lift task were significantly different when compared with those found in control subjects. Among those, the duration of the preloading and loading phases was significantly longer in CH patients. In addition, both the dissimilarity and time-shift between the profiles of the grip and load force rates, quantified with the cross-correlation method, were also significantly larger in CH patients; the time-shift was strongly correlated with impaired dexterity. These findings suggest that impaired dextrous finger movements in CH patients may specifically result from their inability to ensure a precise synergy between fingertip forces while manipulating an object. Finally, the finding that the time-shift also correlated with the corticospinal tract dysgenesis, as estimated with the cerebral peduncle asymmetry, argues in favour of a critical role of the corticospinal system in the temporal coordination between different muscles involved in dextrous hand movements. Both digital and manual dexterity were also altered in the non-paretic hand of CH patients. This deficit may reveal the contribution of the lesioned hemisphere to the control of ipsilateral skilled finger movements.
早期皮质脊髓损伤最具破坏性的后果之一是灵活性受损，这在操作小物体时会导致明显的功能缺陷。本研究的一个目的是调查在先天性偏瘫（CH）患者中，拇指和食指抓握并提起物体时指尖力协调不足在多大程度上可解释其灵活性受损。第二个目的是检查在这些患者中，熟练手部动作的缺陷是否与皮质脊髓束结构损伤的严重程度相关。对16例CH患者（年龄8 - 19岁）和16例年龄及性别匹配的对照受试者进行了精细抓握时指尖力的缩放和协调研究。还对本体感觉、实体觉、压力敏感性和上肢运动功能（包括手指和手部灵活性）进行了定量评估。通过MRI测量脑桥的横截面积并计算两侧脑桥之间的对称指数，来估计皮质脊髓束的结构损伤。与对照受试者相比，CH患者在抓握 - 提起任务中测量的大量参数存在显著差异。其中，CH患者预加载和加载阶段的持续时间明显更长。此外，用互相关方法量化的抓握力和负载力率曲线之间的差异和时间偏移在CH患者中也明显更大；时间偏移与灵活性受损密切相关。这些发现表明，CH患者手指灵巧运动受损可能具体是由于他们在操作物体时无法确保指尖力之间的精确协同作用。最后，时间偏移也与根据脑桥不对称性估计的皮质脊髓束发育异常相关，这一发现支持了皮质脊髓系统在灵巧手部运动中不同肌肉之间的时间协调中起关键作用的观点。CH患者非瘫痪手的手指和手部灵活性也发生了改变。这种缺陷可能揭示了受损半球对同侧熟练手指运动控制的贡献。
