Histological structure of filum terminale in human fetuses.

Object: The structure of the filum terminale (FT) is important in the development of tethered cord syndrome (TCS) in children. Although many studies have been performed on the histological structure of the FT in adults, there has been no detailed investigation for those of fetuses. The aim of this study was to examine the histological structure of the FT in normal human fetuses and to compare the results with those of previous studies.

Methods: The histological examination of the FT was performed in 15 normal human fetuses; 11 of them were female and 4 were male. The gestational age of the fetuses ranged between 14 weeks and 35 weeks, and they weighed between 180 g and 1750 g. The FT of each fetus was cut and examined for adipose tissue, fibrous tissue, peripheral nerve, ganglion, ependymal cells, gliosis, elastic fibers, and collagen types (Types I and III).

Results: Adipose tissue was observed in 2 specimens (13%), whereas fibrous tissue was found in 8 specimens. Peripheral nerve was detected in 11 (73%), ganglion in 6, ependymal cells in 5, and glial tissue in 7 FT samples. Type III collagen was present in 12 specimens (80%) with different concentrations, whereas Type I collagen and elastic fibers were not detected.

Conclusions: The normal structure of the FT in fetuses is different from its structure in adults. The FT has no elasticity during intrauterine life because of the lack of elastic fibers. More detailed studies are needed to understand the histological basis of TCS in children.