Data from: Tactile and proprioceptive dysfunction differentiates cervical dystonia with and without tremor

Objective: To determine if different phenotypes of cervical dystonia (CD) express different types and levels of somatosensory impairment. Methods: We assessed somatosensory function in CD patients with and without tremor (N=12 each) and in healthy age-matched controls (N=22) by measuring tactile temporal discrimination thresholds of the non-dystonic forearm, and proprioceptive acuity in both the dystonic (head/neck) and non-dystonic body segments (forearm/hand) using a joint position-matching task. The head or the wrist was passively displaced along different axes to distinct joint positions by the experimenter or through a robotic exoskeleton. Participants actively reproduced the experienced joint position and the absolute joint position matching error between target and the reproduced positions served as a marker of proprioceptive acuity. Results: Tactile temporal discrimination thresholds were significantly elevated in both CD subgroups when compared to controls. Proprioceptive acuity of both the dystonic and non-dystonic body segments was elevated in patients with CD and tremor with respect to both healthy controls and patients with CD without tremor. That is, tactile abnormalities were a shared dysfunction of both CD phenotypes, while proprioceptive dysfunction was observed in CD patients with tremor. Conclusions: Our findings suggest that the pathophysiology in CD can be characterized by two abnormal neural processes: First, a dysfunctional somatosensory gating mechanism involving the basal ganglia that triggers involuntary muscle spasms. Second, abnormal processing of proprioceptive information within a defective cortico-cerebellar loop, likely affecting the feedback and feedforward control of head positioning. This dysfunction is mainly expressed in CD with tremor.

研究目的：明确不同表型的颈肌张力障碍（cervical dystonia, CD）是否存在不同类型与程度的躯体感觉功能损害。
方法：本研究纳入伴震颤与不伴震颤的CD患者各12例，以及22例年龄匹配的健康对照者。采用关节位置匹配任务，分别检测受试者非肌张力障碍前臂的触觉时间辨别阈值，以及肌张力障碍部位（头/颈部）与非肌张力障碍肢体节段（前臂/手部）的本体感觉敏锐度：由实验人员或通过机器人外骨骼，将受试者头部或腕部沿不同轴被动位移至特定关节位置；随后要求受试者主动复刻所感知的关节位置，以目标位置与复刻位置间的绝对关节匹配误差作为本体感觉敏锐度的量化指标。
结果：与健康对照相比，两个CD亚组的触觉时间辨别阈值均显著升高。伴震颤的CD患者，无论肌张力障碍还是非肌张力障碍肢体节段的本体感觉敏锐度，均显著低于健康对照与不伴震颤的CD患者。换言之，触觉异常是两种CD表型共有的功能障碍，而本体感觉功能障碍仅见于伴震颤的CD患者。
结论：本研究结果提示，CD的病理生理机制可通过两类异常神经过程表征：其一，涉及基底神经节的躯体感觉门控机制功能异常，进而诱发不自主肌肉痉挛；其二，皮质-小脑环路存在缺陷，导致本体感觉信息处理异常，该异常可能影响头部位置的反馈与前馈控制。此类功能障碍主要表现在伴震颤的CD患者中。