Complex Regional Pain Syndrome (CRPS) is characterised by pain, autonomic, sensory and motor abnormalities. It is associated with changes in the primary somatosensory cortex (S1 representation), reductions in tactile sensitivity (tested by two-point discrimination), and alterations in perceived hand size or shape (hand perception). The frequent co-occurrence of these three phenomena has led to the assumption that S1 changes underlie tactile sensitivity and perceptual disturbances. However, studies underpinning such a presumed relationship use tactile sensitivity paradigms that involve the processing of both non-spatial and spatial cues. Here, we used a task that evaluates anisotropy (i.e., orientation-dependency; a feature of peripheral and S1 representation) to interrogate spatial processing of tactile input in CRPS and its relation to hand perception. People with upper limb CRPS (n = 14) and controls with (n = 15) or without pain (n = 19) judged tactile distances between stimuli-pairs applied across and along the back of either hand to provide measures of tactile anisotropy. Hand perception was evaluated using a visual scaling task and questionnaires. Data were analysed with generalised estimating equations. Contrary to our hypotheses, tactile anisotropy was bilaterally preserved in CRPS, and the magnitude of anisotropic perception bias was comparable between groups. Hand perception was distorted in CRPS but not related to the magnitude of anisotropy or bias. Our results suggest against impairments in spatial processing of tactile input, and by implication S1 representation, as the cause of distorted hand perception in CRPS. Further work is warranted to elucidate the mechanisms of somatosensory dysfunction and distorted hand perception in CRPS.

中文翻译：

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完整的触觉各向异性，尽管在复杂的区域性疼痛综合征中手感有所改变：重新思考初级感觉皮层在触觉和知觉功能障碍中的作用

复杂区域性疼痛综合症（CRPS）的特征是疼痛，自主神经，感觉和运动异常。它与初级体感皮层的变化（S1表示），触觉敏感性的降低（通过两点辨别力进行测试）以及感知的手的大小或形状的改变（手的感知）有关。这三种现象的频繁并发导致人们假设S1的变化是触觉敏感性和知觉障碍的基础。但是，支持这种假定关系的研究使用的触觉敏感性范例涉及非空间和空间线索的处理。在这里，我们使用了一个评估各向异性的任务（即方向依赖性；外围功能和S1表示的特征）来询问CRPS中的触觉输入的空间处理及其与手感的关系。上肢CRPS（n = 14）且有控制（n = 15）或没有疼痛（n = 19）的人，判断施加在两只手和手背上的刺激对之间的触觉距离，以提供触觉各向异性的量度。使用视觉缩放任务和问卷对手感进行评估。用广义估计方程分析数据。与我们的假设相反，CRPS双向保留了触觉各向异性，各组之间的各向异性感知偏差的大小相当。在CRPS中，手部感知会失真，但与各向异性或偏倚的大小无关。我们的结果表明，避免在触觉输入的空间处理中出现损害，并暗示S1表示，这是CRPS中手部感知失真的原因。有必要做进一步的工作来阐明CRPS中的体感功能障碍和手部知觉扭曲的机制。