LAUSR

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 showed a linear regression correlation with the gestational week. On an average, the CM migrated from the top third of the L2 vertebra to the L1/2 intervertebral disc level. CONCLUSION The CM may continue 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 should 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. This article is protected by copyright. All rights reserved.