The Distribution of Nerve Endings in the sheath of Human Cervical Nerve Roots, with a Focus on Free Nerve Endings

采用18例死后12小时内尸检的39例颈根-背根神经节标本，对颈神经根硬膜鞘（硬膜根鞘）神经末梢的存在和分布进行了组织病理学研究。年龄4个月~ 88岁，平均58岁。采用铃木银浸渍法或Kluver-Barrera染色法对硬脑膜根鞘各部位的20张连续切片进行显微观察。前根、后根、背根神经节（DRG）的硬脑膜根鞘（包括中隔）各有游离神经末梢，背根神经节和中隔的硬脑膜根鞘各有两种感觉小体。自由神经末梢的纤维直径与阿德尔塔纤维或c纤维的直径一致。游离神经末梢在DRG鞘的近端和远端比硬脑膜根鞘的其他部分分布更多。在容积为0.01 mm^3 （0.16mm^2*0.06mm）的组织圆柱体中，DRG鞘中含有c纤维的游离神经末梢数量最多，为12个，平均3.7个。这些神经末梢被发现遵循两个向心路线中的一个，一个通过脊椎神经，另一个通过从神经末梢直接穿过DRG的小神经。硬脑膜根鞘游离神经末梢数量随年龄增加而增加（γ =0.75）。60岁以下受试者的游离神经末梢数量少于60岁以上受试者，差异有统计学意义（p=0.019）。硬脑膜根鞘中的游离神经末梢，特别是DRG鞘中的游离神经末梢，被认为在介导颈神经根痛中起重要作用。

The presence and distribution of nerve endings in the dural sheath of cervical nerve roots (dural root-sheaths) was investigated histopathologically using 39 cervical root-dorsal root ganglion specimens obtained from 18 postmortem examinations within 12 hours after death. Ages ranged from 4 months to 88 years, with a mean of 58 years. Microscopic investigation was conducted using 20 mum serial sections of various parts of the dural root-sheath, stained by the Suzuki silver impregnation method or Kluver-Barrera method. Free nerve endings were identified in each of the dural root-sheaths of the anterior root, posterior root and dorsal root ganglia (DRG), including the septum, and two types of sensory corpuscles were identified in each of the dural root-sheaths of the dorsal root ganglia and the septum. The fiber diameters of free nerve endings corresponded to those of either Adelta-fibers or C-fibers. The distribution of free nerve endings was greater in the proximal and distal portions of the DRG sheath than in other parts of the dural root-sheath. The largest population of free nerve endings with C-fibers in the DRG sheath was 12 in a tissue cylinder with a volume of 0.01 mm^3 (0.16mm^2*0.06mm), with an average of 3.7. These nerve endings were found to follow either of two centripetal routes, one through a sinuvertebral nerve and the other through small nerves which penetrated directly into the DRG from nerve endings. The number of free nerve endings in the dural root-sheath increased with ages (gamma=0.75). In addition, the number of free nerve endings in subjects below the age of sixty was lower than that of subjects above sixty with a statistical significance (p=0.019). These free nerve endings in the dural root-sheath, especially those in the DRG sheath, are thought to play an important role in the mediation of cervical radicular pain.