Ramalho Bia Lima, Rangel Maria Luíza, Schmaedeke Ana Carolina, Erthal Fátima Smith, Vargas Claudia D
Laboratory of Neurobiology of Movement, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Laboratory of Neuroscience and Rehabilitation, Institute of Neurology Deolindo Couto, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Front Neurol. 2019 Aug 13;10:872. doi: 10.3389/fneur.2019.00872. eCollection 2019.
Unilateral brachial plexus injury (BPI) impairs sensory and motor functions of the upper limb. This study aimed to map in detail brachial plexus sensory impairment both in the injured and the uninjured upper limb. Touch sensation was measured through Semmes-Weinstein monofilaments at the autonomous regions of the brachial plexus nerves, hereafter called points of exclusive innervation (PEIs). Seventeen BPI patients (31.35 years±6.9 SD) and 14 age-matched healthy controls (27.57 years±5.8 SD) were tested bilaterally at six selected PEIs (axillary, musculocutaneous, median, radial, ulnar, and medial antebrachial cutaneous [MABC]). As expected, the comparison between the control group and the brachial plexus patients' injured limb showed a robust difference for all PEIs ( ≤ 0.001). Moreover, the comparison between the control group and the brachial plexus uninjured limb revealed a difference for the median ( = 0.0074), radial ( = 0.0185), ulnar ( = 0.0404), and MABC ( = 0.0328) PEIs. After splitting the sample into two groups with respect to the dominance of the injured limb, higher threshold values were found for the uninjured side when it occurred in the right dominant limb compared to the control group at the median ( = 0.0456), radial ( = 0.0096), and MABC ( = 0.0078) PEIs. This effect was absent for the left, non-dominant arm. To assess the effect of the severity of sensory deficits observed in the injured limb upon the alterations of the uninjured limb, a K-means clustering algorithm (k = 2) was applied resulting in two groups with less or more severe sensory impairment. The less severely affected patients presented higher thresholds at the median ( = 0.0189), radial ( = 0.0081), ulnar ( = 0.0253), and MABC ( = 0.0187) PEIs in the uninjured limb in comparison with the control group, whereas higher thresholds at the uninjured limb were found only for the median PEI ( = 0.0457) in the more severely affected group. In conclusion, an expressive reduction in touch threshold was found for the injured limb allowing a precise mapping of the impairment caused by the BPI. Crucially, BPI also led to reduced tactile threshold in specific PEIs in the uninjured upper limb. These new findings suggest a superordinate model of representational plasticity occurring bilaterally in the brain after a unilateral peripheral injury.
单侧臂丛神经损伤（BPI）会损害上肢的感觉和运动功能。本研究旨在详细描绘受伤上肢和未受伤上肢的臂丛神经感觉障碍情况。通过Semmes-Weinstein单丝在臂丛神经的自主区域测量触觉，以下称为专属支配点（PEIs）。对17例BPI患者（31.35岁±6.9标准差）和14例年龄匹配的健康对照者（27.57岁±5.8标准差）在六个选定的PEIs（腋神经、肌皮神经、正中神经、桡神经、尺神经和前臂内侧皮神经[MABC]）进行双侧测试。正如预期的那样，对照组与臂丛神经损伤患者的受伤肢体之间的比较显示，所有PEIs均存在显著差异（≤0.001）。此外，对照组与臂丛神经未受伤肢体之间的比较显示，正中神经（=0.0074）、桡神经（=0.0185）、尺神经（=0.0404）和MABC（=0.0328）PEIs存在差异。根据受伤肢体的优势将样本分为两组后发现，当未受伤侧为右侧优势肢体时，与对照组相比，在正中神经（=0.0456）、桡神经（=0.0096）和MABC（=0.0078）PEIs处的阈值更高。左侧非优势手臂未出现这种效应。为了评估受伤肢体中观察到的感觉缺陷严重程度对未受伤肢体改变的影响，应用了K均值聚类算法（k = 2），结果分为两组，感觉障碍较轻或较重。与对照组相比，受影响较轻的患者在未受伤肢体的正中神经（=0.0189）、桡神经（=0.0081）、尺神经（=0.0253）和MABC（=0.0187）PEIs处呈现出更高的阈值，而在受影响较重的组中，仅在正中神经PEI（=0.0457）处发现未受伤肢体的阈值较高。总之，发现受伤肢体的触觉阈值有明显降低，从而能够精确描绘由BPI引起的损伤。至关重要的是，BPI还导致未受伤上肢特定PEIs处的触觉阈值降低。这些新发现提示了一种单侧外周损伤后双侧大脑中发生的表征可塑性的上位模型。
