Objectives

Altered cortical visuomotor integration has been involved in the pathophysiology of freezing of gait (FoG) in parkinsonism. The aim of this study was to assess the connections between the primary visual (V1) and motor (M1) areas with a paired-pulse, twin-coil transcranial magnetic stimulation (TMS) technique in patients with FoG.

Methods

Twelve Parkinson's disease (PD) patients suffering from levodopa-responsive-FoG (off-FoG) were compared with 12 PD patients without FoG and 12 healthy subjects of similar age/sex. In the “off” condition, visuomotor connections (VMCs) were assessed bilaterally. A conditioning stimulus over the V1 phosphene hotspot was followed at interstimulus intervals (ISIs) of 18 and 40 ms by a test stimulus over M1, to elicit motor evoked potentials (MEPs) in the contralateral first dorsal interosseous muscle.

Results

Significant (P < 0.01), bilateral effects due to VMCs were detected in all three groups, consisting of a MEP suppression at ISI 18 and 40 ms. However, in PD patients with FoG, the MEP suppression was significantly (P < 0.05) enhanced, both at ISI 18–40 ms, in comparison with the other two groups. The phenomenon was limited to the right hemisphere.

Conclusions

PD patients with FoG showed an excessive inhibitory response of the right M1 to inputs travelling from V1 at given ISIs. Right-sided alterations of the cortical visuomotor integration may contribute to the pathophysiology of FoG.

中文翻译：

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步态冻结中的皮质视觉运动相互作用：一种TMS方法。

目标

帕金森病中步态冻结（FoG）冻结的病理生理学涉及改变的皮层视觉运动整合。这项研究的目的是通过双脉冲双线圈经颅磁刺激（TMS）技术评估FoG患者的主要视觉（V1）和运动（M1）区域之间的联系。

方法

将十二名帕金森病（PD）左旋多巴反应性FoG（off-FoG）患者与12名无FoG的PD患者和12名年龄/性别相似的健康受试者进行比较。在“关闭”状态下，双侧评估运动连接（VMC）。在V1 phosph热点上进行条件刺激，然后在M1上进行测试刺激，间隔时间为18和40 ms，以激发对侧第一背骨间肌的运动诱发电位（MEP）。

结果

在所有三组中均检测到了显着（P  <0.01）的由VMC引起的双边影响，包括在ISI 18和40 ms处的MEP抑制。然而，与其他两组相比，在ISI 18–40 ms时，患有FoG的PD患者的MEP抑制均显着增强（P  <0.05）。这种现象仅限于右半球。

结论

患有FoG的PD患者显示，在给定的ISI下，右M1对从V1行进的输入的过度抑制反应。皮质视觉运动整合的右侧改变可能有助于FoG的病理生理。