Hettinger Patrick C, Li Rupeng, Yan Ji-Geng, Cho Younghoon R, Sanger James, Dzwierzynski William, Pawela Christopher P, Hyde James S, Matloub Hani S
Hand (N Y). 2011 Jun;6(2):194-201. doi: 10.1007/s11552-011-9319-7. Epub 2011 Feb 19.
Since the 1980s, the C7 nerve root has gained clinical relevance as a donor nerve in severe brachial plexus root avulsion injuries. Despite success with the cross-chest C7 nerve transfer, inducing injury on an otherwise normal side hinders global acceptance. By sacrificing the C7 nerve root, a predictable pattern of transient sequelae is seen, including extensor weakness and index and middle finger anesthesia. The purpose of this study is to observe cortical activity during direct stimulation of the C7 nerve root using blood oxygen level dependent functional magnetic resonance imaging (fMRI) in a rat model.
A total of 12 male Sprague-Dawley rats, weighing 200-250 g, were used in this study. Following an acclimation period of 1 week, 12 rats underwent exposure and dissection of the brachial plexus. Seven rats underwent placement of an implantable electrode (AISI 304, Plastics1, Roanoke, VA, USA) on the C7 nerve root, while five rats underwent electrode placement on the radial nerve. All animals then underwent fMRI during direct nerve stimulation. Ten consecutive coronal images were obtained during nerve stimulation, using a 9.4-T small-animal MRI scanner.
Cortical activation is seen within a very specific area of the primary sensory region of the forelimb during C7 nerve root stimulation. The cortical activation seen during radial nerve stimulation includes that seen during C7 stimulation but extends several slices caudally.
The sensory representation of the C7 nerve root is seen in only a small area in the S1FL region compared to that seen in the terminal branches of the brachial plexus. However, this area shows a significant overlap with the S1FL area of activation seen during radial nerve stimulation. This makes sense as the C7 nerve root contributes some, but not all, sensory axons to the radial nerve. Mapping of the C7 cortical representation in the rat brain not only adds to the ongoing development of the motor and sensory ratunculus but also provides an important foundation to study subsequent C7 donor nerve models.
自20世纪80年代以来，C7神经根在严重臂丛神经根撕脱伤中作为供体神经已具有临床意义。尽管跨胸C7神经移位取得了成功，但在原本正常的一侧造成损伤阻碍了其广泛应用。通过牺牲C7神经根，会出现一系列可预测的短暂后遗症，包括伸肌无力以及示指和中指麻木。本研究的目的是在大鼠模型中，使用血氧水平依赖性功能磁共振成像（fMRI）观察直接刺激C7神经根时的皮质活动。
本研究共使用12只体重200 - 250克的雄性Sprague-Dawley大鼠。经过1周的适应期后，12只大鼠接受臂丛神经的暴露和解剖。7只大鼠在C7神经根上放置可植入电极（AISI 304，Plastics1，美国弗吉尼亚州罗阿诺克），而5只大鼠在桡神经上放置电极。然后所有动物在直接神经刺激期间接受fMRI检查。使用9.4-T小动物MRI扫描仪在神经刺激期间获取10个连续的冠状图像。
在C7神经根刺激期间，在前肢初级感觉区域的一个非常特定的区域内可见皮质激活。在桡神经刺激期间看到的皮质激活包括在C7刺激期间看到的激活，但向尾侧延伸了几个层面。
与臂丛神经终末分支相比，C7神经根的感觉代表仅在S1FL区域的一个小区域中可见。然而，该区域与桡神经刺激期间看到的S1FL激活区域有明显重叠。这是合理的，因为C7神经根为桡神经贡献了一些但不是全部的感觉轴突。大鼠脑中C7皮质代表区的映射不仅有助于运动和感觉大鼠脑图谱的持续发展，也为研究后续C7供体神经模型提供了重要基础。
