Abstract
Epidural blocks have been used extensively in infants. However, little histological information is available on the immature neural-dural transition. The neural-dural transition was histologically investigated in 12 late-stage (28–30 weeks) fetuses. The dural sheath of the spinal cord was observed to always continue along the nerve roots with varying thicknesses between specimens and segments, while the dorsal root ganglion sheath was usually very thin or unclear. Immature neural-dural transitions were associated with effective anesthesia. The posterior radicular artery was near the dorsal root ganglion and/or embedded in the nerve root, whereas the anterior radicular artery was separated from the nearest nerve root. The anterior radicular artery was not associated with the dural sheath but with thin mesenchymal tissue. The numbers of radicular arteries tended to become smaller in larger specimens. Likewise, larger specimens of the upper thoracic and lower lumbar segments did not show the artery. Therefore, elimination of the radicular arteries to form a single artery of Adamkiewicz was occurring in late-stage fetuses. The epidural space was filled with veins, and the loose tissue space extended ventrolaterally to the subpleural tissue between the ribs. Consequently, epidural blocks in infants require special attention although immature neural-dural transitions seemed to increase the effect.
Highlights
Epidural blocks have been used extensively in infants [1], with transesophageal echocardiography providing good guidance for anesthesiologists [2]
To the best of our knowledge, the human fetus materials examined in most previous studies of the spinal dura [3, 4] were from the embryonic and early fetal periods and not the late fetal stages as those studies focused on the origin and differentiation of these structures and not their topographical anatomy
In the frontal and tilted frontal sections, the nerve root and its associated dorsal root ganglion (DRG) were not usually seen in the series of continuous multiple segments but were seen in the 2-3 segments that were between them, which was possibly due to slight curvature of the vertebral column (Figures 1 and 2)
Summary
Epidural blocks have been used extensively in infants [1], with transesophageal echocardiography providing good guidance for anesthesiologists [2]. Limited histological information was provided about older fetuses (15–30 weeks) by Jin et al [6] who showed that the basic configuration of the fetal dura is comprised of the periosteal and meningeal layers, which is similar to that in adults. Their focus was not on the neural-dural transition but on ossification in the posterior longitudinal ligaments. In order to elucidate basic anatomical information in order to allow for the conductance of safe and reasonable anesthesia and surgery of the infant spinal cord, we aimed to examine the structures surrounding the nerve roots in histological sections of late-stage fetuses
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