Background

Somatotopy is considered the hallmark of the primary motor cortex. While this is fundamentally true for the major body parts (head, upper and lower extremities), evidence supporting the existence of within-limb somatotopy is scarce.

Method

We report a young man presenting recurrent ischemic strokes with selective finger weakness in whom serial motor cortex mapping procedures were performed.

Result

Following the first stroke, which largely spared the motor cortex, motor mapping displayed overlap of the motor representations of the hand muscles. The second focal stroke, affecting the lateral part of the hand knob, resulted in selective loss of the first dorsal interosseous muscle motor evoked potentials while sparing those of the adductor digiti minimi muscle. This observation is in apparent contradiction with the first mapping results that suggested complete overlap of motor representations.

Discussion

Our mapping results provide evidence for the existence of very precise within-limb somatotopy and confirm the proposed homuncular order, whereby lateral fingers are represented laterally and medial fingers medially. The discrepancy between the initial and subsequent mapping results is discussed in light of functional organization of the primary motor cortex.

中文翻译：

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局灶性运动皮层损伤揭示了精确的手指解剖

背景

躯体解剖被认为是初级运动皮层的标​​志。尽管对于主要身体部位（头部，上肢和下肢）从根本上来说是正确的，但缺乏支持肢体内部躯体解剖学存在的证据。

方法

我们报告一个年轻人表现出复发性缺血性中风与选择性手指无力，其中执行串行运动皮层映射程序。

结果

在第一笔运动之后，这在很大程度上节省了运动皮层，运动映射显示出手部肌肉的运动表示重叠。第二个中风影响了旋钮的外侧部分，导致第一背骨间肌肉运动诱发电位的选择性损失，同时保留了小指内收肌的电位。此观察结果与第一个映射结果明显矛盾，后者表明运动表示完全重叠。

讨论区

我们的作图结果提供了非常精确的下肢内部躯体解剖学存在的证据，并证实了所提出的单亲顺序，其中外侧手指代表外侧，内侧手指代表内侧。根据主要运动皮层的功能组织，讨论了初始映射结果和后续映射结果之间的差异。