Conus medullaris migration during the third trimester: A retrospective study
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Published on: September 18, 2013
Mengchun Sun1,2, Benzhang Tao1, Gan Gao1
1Department of Neurosurgery, The First Medical Center of Chinese PLA General Hospital, Beijing, China.
Objective:
To explore the migration process of the conus medullaris (CM) and propose a normal range of CM levels during the third trimester.
Method:
We retrospectively collected the ultrasonographic and clinical data of 588 fetuses during the third trimester. We located the CM and assigned scores. One-way analysis of variance and linear regression analyses were used to statistically analyze CM migration. Statistical significance was set at p < 0.05.
Results:
The CM levels were statistically different among the different gestational weeks of the third trimester. The CM level showed a linear regression correlation with the gestational weeks. On an average, the CM migrated from the top third of the L2 vertebra to the L1/2 intervertebral disc level.
Conclusion:
The CM continues to migrate, from the top third of the L2 vertebra to the L1/2 intervertebral disc level, during the third trimester. The term infant could have the CM at the normal adult level at birth. At the beginning of the third trimester, a CM located above the L2/3 intervertebral disc level could be normal; the CM location at the L3 vertebra level could be physiological and needs follow-up; and a CM presenting below the L3 vertebra level might indicate tethered cord syndrome. The fetus with a CM significantly above the L1/2 intervertebral disc level may have caudal regression syndrome.
