Changes in Length of the Spinal Cord and Vertebral Level of the Termination of the Spinal Cord in Korean Fetuses

Kang, Ho Suck; Cho, Byung Pil; Kim, Ji Won; Song, Dae Yong; Yang, Young Chul; Park, Jung Cheol

Abstract

It has been reported that there are racial differences in the vertebral level of termination of the spinal cord (VLTS) in fetuses. However, the precise analysis about the differences has not been established because the definition of the termination of the spinal cord used in comparing the VLTS was different from one another. The purpose of this study is to measure the VLTS, the length of the spinal cord and vertebral column in Korean fetuses, and to compare the VLTS with that of other nations or races according to the different definitions of the termination of the spinal cord. Two points were considered to measure the length and vertebral level of the spinal cord: One point was where the lowest spinal nerve root emerges (termination of the spinal cord I, SCT I), and the other was the point at which the tapering of the conus medullaris suddenly stops, and after which the diameter remains about the same (termination of the spinal cord II, SCT II). Materials used for this study were 115 normal Korean fetuses ranging from 13th to 37th weeks after the onset of the last normal menstrual period (LNMP). The fetuses were subdivided into 7 groups by gestational age and crownrump length (CRL), respectively. The results were obtained as follows. 1. All lengths of the vertebral column (VCL), spinal cord (SCL) and dura mater (DML) increased with the increase in fetal age, but the rate was somewhat different from one another. Especially, the increase rate of SCL was lowered at 6th month of gestation (Group III). Recession lengths of the two terminations of the spinal cord were also greatest in Group III and the ratio of SCL to VCL was also decreased greatly in Group III. These findings indicate that the relative growth rate of the spinal cord to the vertebral column is lowest during the 6th month, and as a result, the spinal cord ascends most rapidly during this stage of development. The number of cases after 8th month was so few that we could not make any conclusion. 2. With the increase in fetal age, vertebral level and range of the termination of the spinal cord and the dura mater increased gradually. In comparison of our results with others, we confirmed that the vertebral level of the termination of the spinal cord in Korean fetus is similar to that of Saudi Arabian, but is somewhat higher than that of the English, North Indian and South Indian. 3. There was no statistically significant difference between male and female in all measurements except for a very few ones.