Ultrasound determination of the normal location of the conus medullaris in neonates

Abstract

Purpose: To establish the normal range of the position of the conus medullaris in neonates and determine whether it differs from that in adults.

Methods: One hundred five healthy neonates born over an 18-day period in a single obstetric unit had ultrasound examinations of their lower spines to relate the conus medullaris to the nearest intervertebral disk or midvertebral level.

Results: The mean position of the conus was midway between the L1-2 disk and mid-L-2 body, ranging from T-12/L-1 to L-3, with the modal position being L1-2 (47.6%). A small but significant rise in position from 33 to 42 weeks postconceptual age was identified. Comparison with data previously reported from adults showed a small but highly significant difference in conus position of approximately 0.25 vertebral levels.

Discussion: Our data confirm studies suggesting that ascent of the cord after birth is minor.