Background/Objective. Position sense, defined as the ability to identify joint and limb position in space, is crucial for balance and gait but has received limited attention in patients with multiple sclerosis (MS). We investigated lower limb position sense deficits, their neural correlates, and their effects on standing balance in patients with early MS. Methods. A total of 24 patients with early relapsing-remitting MS and 24 healthy controls performed ipsilateral and contralateral matching tasks with the right foot during functional magnetic resonance imaging. Corpus callosum (CC) integrity was estimated with diffusion tensor imaging. Patients also underwent an assessment of balance during quiet standing. We investigated differences between the 2 groups and the relations among proprioceptive errors, balance performance, and functional/structural correlates. Results. During the contralateral matching task, patients demonstrated a higher matching error than controls, which correlated with the microstructural damage of the CC and with balance ability. In contrast, during the ipsilateral task, the 2 groups showed a similar matching performance, but patients displayed a functional reorganization involving the parietal areas. Neural activity in the frontoparietal regions correlated with the performance during both proprioceptive matching tasks and quiet standing. Conclusion. Patients with early MS had subtle, clinically undetectable, position sense deficits at the lower limbs that, nevertheless, affected standing balance. Functional changes allowed correct proprioception processing during the ipsilateral matching task but not during the more demanding bilateral task, possibly because of damage to the CC. These findings provide new insights into the mechanisms underlying disability in MS and could influence the design of neurorehabilitation protocols.

中文翻译：

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早期多发性硬化症中下肢的位置觉缺陷：临床和神经相关性

背景/目标。位置感，定义为在空间中识别关节和肢体位置的能力，对平衡和步态至关重要，但在多发性硬化症 (MS) 患者中受到的关注有限。我们调查了下肢位置感觉缺陷、它们的神经相关性以及它们对早期 MS 患者站立平衡的影响。方法。共有 24 名早期复发缓解型 MS 患者和 24 名健康对照者在功能磁共振成像期间与右脚执行同侧和对侧匹配任务。胼胝体 (CC) 完整性通过扩散张量成像进行评估。患者还接受了安静站立时的平衡评估。我们调查了两组之间的差异以及本体感觉错误、平衡表现、和功能/结构相关。结果。在对侧匹配任务中，患者表现出比对照组更高的匹配误差，这与 CC 的微观结构损伤和平衡能力有关。相比之下，在同侧任务中，两组表现出相似的匹配表现，但患者表现出涉及顶叶区域的功能重组。额顶区域的神经活动与本体感觉匹配任务和安静站立期间的表现相关。结论。早期 MS 患者在下肢有细微的、临床上无法检测到的位置觉缺陷，但会影响站立平衡。功能变化允许在同侧匹配任务期间正确的本体感觉处理，但在要求更高的双边任务期间则不允许，可能是因为 CC 损坏。这些发现为 MS 残疾的潜在机制提供了新的见解，并可能影响神经康复方案的设计。