对侧外周神经移位到损伤手臂引起的体感皮层功能动态重组

摘要

单侧肢体的外周神经损伤通常导致对侧体感皮层的功能重组.然而,接受了对侧颈7(C7)外周神经移位手术治疗单侧手臂臂丛全撕脱的病人,在术后早期当其患手被触摸时,只在其健手产生感觉.在术后晚期,病人才逐渐恢复其患手和健手的正常、独立的功能.我们在模拟对侧颈7(C7)外周神经移位手术病例的大鼠模型上,用记录体感诱发电位的方法研究了患手和健手的体感代表区.患手的体感和运动功能由于C7神经的再生而逐渐恢复.术后第5个月始,13只大鼠患手的体感代表区只出现在其同侧的皮层,同时患手和健手的代表区在该皮层内是高度重叠的(除掉一个例外),虽然刺激它们产生的体感诱发电位的潜伏期和反应幅度有很大的不同.结果表明,移位到患手的对侧外周神经能够导致同侧体感皮层动态的功能重组,提示身体另侧感觉输入的介入激发了大脑显著的可塑性.%Peripheral nerve injury of a limb usually causes functional reorganization of the contralateral somatosensory cortex.However, the patients with an operation of the contralateral seventh cervical nerve (C7) transfer to an injured arm with brachial plexus root avulsions usually have the sole tactile sensibility of the healthy hand when the injured hand is touched at the early stage after the operation. Then, at later stage they gradually get normal sense from the injured and the normal hands independently. Mimicked the process in a rat model based on the above operation, representations of the injured forepaw and the healthy forepaw in the somatosensory cortex were studied by means of somatosensory evoked potential (SEP) recording. Somatosensory function shown in SEP response amplitude and peak latency of the injured forepaw gradually recovered with time after the operation due to the contralateral C7 regeneration toward the injured limb, accompanied with the recovery process of limb movement. The somatosensory representation of the injured forepaw was observed exclusively in the ipsilateral somatosensory cortex since the 5th month after the operation. Accordingly, the overlapped representation of the injured and healthy forepaws emerged in the ipsilateral somatosensory cortex of 13 rats studied except one with separated representation though the SEP latency and response amplitude were different in responding to stimuli on the two forepaws. It is concluded that the contralateral peripheral nerve transfer to the injured arm can cause dynamically functional reorganization in the ipsilateral somatosensory cortex suggesting a remarkable plasticity of the brain function induced by an alteration of sensory input between two sides of the body in adult rats.