Parke W W, Watanabe R
J Neurosurg. 1987 Aug;67(2):269-77. doi: 10.3171/jns.1987.67.2.0269.
An epispinal system of motor axons virtually covers the ventral and lateral funiculi of the human conus medullaris between the L-2 and S-2 levels. These nerve fibers apparently arise from motor cells of the ventral horn nuclei and join spinal nerve roots caudal to their level of origin. In all observed spinal cords, many of these axons converged at the cord surface and formed an irregular group of ectopic rootlets that could be visually traced to join conventional spinal nerve roots at one to several segments inferior to their original segmental level; occasional rootlets joined a dorsal nerve root. As almost all previous reports of nerve root interconnections involved only the dorsal roots and have been cited to explain a lack of an absolute segmental sensory nerve distribution, it is believed that these intersegmental motor fibers may similarly explain a more diffuse efferent distribution than has previously been suspected.
运动轴突的脊髓外系统实际上覆盖了人类脊髓圆锥L-2至S-2节段之间的腹侧和外侧索。这些神经纤维显然起源于腹角核的运动细胞，并在其起源水平以下加入尾侧的脊神经根。在所有观察到的脊髓中，许多这些轴突在脊髓表面汇聚，形成一组不规则的异位小根，在视觉上可以追踪到它们在比其原始节段水平低一至几个节段处与传统脊神经根相连；偶尔有小根与背神经根相连。由于几乎所有先前关于神经根互连的报告仅涉及背根，并且已被引用来解释缺乏绝对节段性感觉神经分布的现象，因此人们认为这些节段间运动纤维可能同样解释了比先前怀疑的更广泛的传出分布。
