Kitamura Kei, Yamamoto Masahito, Hirota Yoshinosuke, Sato Noriyuki, Machida Toshimasa, Ishikawa Noboru, Yamamoto Hitoshi, Murakami Gen, Abe Shinichi
Department of Histology and Embryology, Tokyo Dental College, Tokyo, Japan.
Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
Anat Cell Biol. 2020 Dec 31;53(4):451-459. doi: 10.5115/acb.20.081.
We have previously reported that the thoracolumbar posterior nerve root shows a tortuous epidural course, based on studies of human fetuses near term. For comparison with the cervical nerve, examinations were conducted using frontal, sagittal and horizontal sections of cervical vertebrae from 22 fetuses at 30-38 weeks of gestation. The cervical nerve root showed a short, straight and lateral course near the zygapophysial joint. Multiple rather than single bundles of the cervical posterior root seemed to account for the majority of sensory nerve fibers innervating the upper extremity. Fasciculation of rootlets was evident near the thoracolumbar spinal cord, whereas it was seen in the dural pocket at the nerve exit from the dural sac although both sites were subdural. As in the thoracolumbar region, the nerve sheath was continuous with the dura mater and independently surrounded each of the anterior and posterior roots. Radicular arteries were few in the cervical region. In 2 of the 22 fetuses (31 weeks and 33 weeks), there was a segmental, unilateral abnormality of nerve rootlet fasciculation where the dorsal root ganglion was located lateral or peripheral to the intervertebral region. Long nerve roots running inferiorly are a necessary adaptation to the delayed and marked growth of the thoracolumbar vertebral column. In children, the cervical nerve roots are likely to be affected by movement or dislocation of the vertebrae. The segmental abnormality of the cervical nerve root may be linked to rare variations in the brachial plexus.
我们之前曾报道，基于对近期人类胎儿的研究，胸腰段后神经根在硬膜外走行呈迂曲状。为了与颈神经作比较，我们对22例妊娠30 - 38周胎儿的颈椎进行了额状面、矢状面和水平面切片检查。颈神经根在关节突关节附近走行短、直且呈外侧走行。颈后根似乎是多束而非单束，这似乎构成了支配上肢的感觉神经纤维的大部分。神经根丝在胸腰段脊髓附近明显呈束状，而在硬膜囊神经穿出的硬膜腔内也可见到，尽管这两个部位都在硬膜下。与胸腰段区域一样，神经鞘与硬脊膜连续，并分别独立包绕前根和后根。颈段的根动脉较少。在22例胎儿中的2例（31周和33周），在背根神经节位于椎间区域外侧或周边处，存在神经根丝束状的节段性、单侧异常。向下走行的长神经根是对胸腰段脊柱延迟且显著生长的一种必要适应。在儿童中，颈神经根可能会受到椎体运动或脱位的影响。颈神经根的节段性异常可能与臂丛神经的罕见变异有关。
