Interlimb reflexes and synaptic plasticity become evident months after human spinal cord injury
Interlimb reflexes and synaptic plasticity become evident months after human spinal cord injury
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DOI：
10.1093/brain/awf114
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发表时间：
2002-05-01
期刊：
影响因子：
14.5
通讯作者：
Broton, JG
中科院分区：
文献类型：
--
作者：
Calancie, B;Molano, MR;Broton, JG
颈脊髓长期损伤导致完全或部分瘫痪的患者通常会在损伤水平尾部接受神经支配的肌肉中出现广泛的不自主运动。我们之前已经证明，这些运动包括手和前臂肌肉的短暂和离散收缩，以响应对脚和腿的无害感觉刺激，但我们一直无法在身体健全的受试者中复制这些肢体间反射。这些肌肉反应的性质表明，颈膨大的上行感觉纤维和运动神经元之间的突触接触比正常情况下更有效。如果这些连接在任何时候都存在，并且需要更多的吻部脊髓损伤才能出现，那么人们可能会期望它们在损伤后相对较快地出现，正如“潜伏”突触的研究所示。相反，这些肢体间反射的延迟出现表明，由于传入靶点丢失和运动神经元去神经支配从运动束起源于损伤部位的吻侧的组合，颈脊髓中新的突触连接的发展或现有回路的深刻加强。在这项研究中，我们对急性颈脊髓损伤的患者进行了重复检查，以检查损伤后首次出现肢体间反射的时间。使用膝关节胫神经刺激作为筛选试验，共发现24名受试者在脊髓损伤后出现肢体间反射。刺激和EMG之间的延迟对于前臂肌肉为32 ms，对于手部肌肉为44 ms。这些微小的延迟几乎排除了这些肢体间反射的脊髓上路径。肢体间反射在受伤后6个月开始出现，有些人直到受伤后1年才出现。增强的下肢节段性兴奋性出现在几乎所有这些科目的第一次出现肢体间反射前几周或几个月，反对传统的创伤后痉挛的表现作为这种活动的基础。这种损伤时间和肢体间反射活动出现之间的延迟延长支持了这样一种假设，即这种活动代表了人类脊髓创伤后可塑性的一个例子，也许是“再生发芽”。
Persons with long-standing injury to the cervical spinal cord resulting in complete or partial paralysis typically develop a wide spectrum of involuntary movements in muscles receiving innervation caudal to the level of injury. We have previously shown that these movements include brief and discrete contraction of muscles in the hand and forearm in response to innocuous sensory stimulation to the feet and legs, but we have been unable to replicate these interlimb reflexes in able-bodied subjects. Properties of these muscle responses indicate that the synaptic contacts between ascending sensory fibres and motor neurones of the cervical enlargement are more efficacious than normal. If these connections are present at all times, and require the more rostrally-placed spinal cord injury to allow their emergence, one might expect their appearance relatively soon following injury, as has been shown for studies of 'latent' synapses. Conversely, delayed appearance of these interlimb reflexes would suggest either the development of new synaptic connections or a profound strengthening of existing circuits in the cervical spinal cord due to a combination of afferent target loss and motor neurone denervation from motor tracts originating rostral to the injury site. In this study, we used repeated examinations of persons with acute injury to the cervical spinal cord to examine the time post-injury at which interlimb reflexes are first seen. Using tibial nerve stimulation at the knee as a screening test, a total of 24 subjects were found to develop interlimb reflexes following spinal cord injury. Latencies between stimulation and EMG were as brief as 32 ms for muscles of the forearm and 44 ms for muscles in the hand. These minimal delays all but rule out a supraspinal route for these interlimb reflexes. Interlimb reflexes first became evident no sooner than similar to6 months following injury, and in some individuals were not seen until well over 1 year post-injury. Enhanced lower limb segmental excitability had emerged in nearly all of these subjects weeks or months prior to the first appearance of interlimb reflexes, arguing against a manifestation of traditional post-traumatic spasticity as a basis for this activity. This prolonged delay between time of injury and emergence of interlimb reflex activity lends support to the hypothesis that this activity represents an example of plasticity-and perhaps 'regenerative sprouting'-in the human spinal cord following traumatic injury.