Topka H, Konczak J, Dichgans J
Department of Neurology, University of Tübingen, Germany.
Exp Brain Res. 1998 Apr;119(4):483-92. doi: 10.1007/s002210050364.
Kinematic abnormalities of fast multijoint movements in cerebellar ataxia include abnormally increased curvature of hand trajectories and an increased hand path and are thought to originate from an impairment in generating appropriate levels of muscle torques to support normal coordination between shoulder and elbow joints. Such a mechanism predicts that kinematic abnormalities are pronounced when fast movements are performed and large muscular torques are required. Experimental evidence that systematically explores the effects of increasing movement velocities on movement kinematics in cerebellar multijoint movements is limited and to some extent contradictory. We, therefore, investigated angular and hand kinematics of natural multijoint pointing movements in patients with cerebellar degenerative disorders and healthy controls. Subjects performed self-paced vertical pointing movements with their right arms at three different target velocities. Limb movements were recorded in three-dimensional space using a two-camera infrared tracking system. Differences between patients and healthy subjects were most prominent when the subjects performed fast movements. Peak hand acceleration and deceleration were similar to normals during slow and moderate velocity movements but were smaller for fast movements. While altering movement velocities had little or no effect on the length of the hand path and angular motion of elbow and shoulder joints in normal subjects, the patients exhibited overshooting motions (hypermetria) of the hand and at both joints as movement velocity increased. Hypermetria at one joint always accompanied hypermetria at the neighboring joint. Peak elbow angular deceleration was markedly delayed in patients compared with normals. Other temporal movement variables such as the relative timing of shoulder and elbow joint motion onsets were normal in patients. Kinematic abnormalities of multijoint arm movements in cerebellar ataxia include hypermetria at both the elbow and the shoulder joint and, as a consequence, irregular and enlarged paths of the hand, and they are marked with fast but not with slow movements. Our findings suggest that kinematic movement abnormalities that characterize cerebellar limb ataxia are related to an impairment in scaling movement variables such as joint acceleration and deceleration normally with movement speed. Most likely, increased hand paths and decomposition of movement during slow movements, as described earlier, result from compensatory mechanisms the patients may employ if maximum movement accuracy is required.
小脑共济失调中快速多关节运动的运动学异常包括手部轨迹曲率异常增加和手部路径变长，被认为源于产生适当水平肌肉扭矩以支持肩肘关节正常协调的功能受损。这种机制预测，当进行快速运动且需要较大肌肉扭矩时，运动学异常会很明显。系统探究增加运动速度对小脑多关节运动中运动学影响的实验证据有限，且在某种程度上相互矛盾。因此，我们研究了小脑退行性疾病患者和健康对照者自然多关节指向运动的角度和手部运动学。受试者用右臂以三种不同目标速度进行自定节奏的垂直指向运动。使用双摄像头红外跟踪系统在三维空间中记录肢体运动。当受试者进行快速运动时，患者与健康受试者之间的差异最为显著。在慢速和中速运动期间，手部峰值加速度和减速度与正常人相似，但在快速运动时较小。虽然改变运动速度对正常受试者手部路径长度以及肘关节和肩关节的角运动几乎没有影响，但随着运动速度增加，患者的手部以及两个关节都出现了过冲运动（辨距过度）。一个关节的辨距过度总是伴随着相邻关节的辨距过度。与正常人相比，患者的肘关节峰值角减速明显延迟。患者的其他时间运动变量，如肩关节和肘关节运动起始的相对时间是正常的。小脑共济失调中多关节手臂运动的运动学异常包括肘关节和肩关节的辨距过度，因此手部路径不规则且变长，并且这些异常在快速运动而非慢速运动时明显。我们的研究结果表明，小脑肢体共济失调特征性的运动学运动异常与正常情况下根据运动速度缩放关节加速度和减速度等运动变量的功能受损有关。如前所述，慢速运动时手部路径增加和运动分解很可能是患者在需要最大运动精度时可能采用的补偿机制的结果。
