The conus medullaris: time of ascendence to normal level.

This study was intended to determine the level of the conus medullaris in normal babies. We examined 114 healthy infants using high resolution ultrasound which identified the spinal cord and the tip of the conus medullaris. This method provided a good analysis of the level of the conus medullaris so that we could assess the rate of ascent to L1/2. The range of the conus level for all children was at TH12/L1 interspace to L4.78% of babies aged between the 30th and 39th postmenstrual week had the tip of the conus medullaris between L2 and L4.84% of babies aged between the 40th and 63rd postmenstrual week had their conus level between TH12/L1 and L1/2 interspace. In one girl aged 53 weeks the tip was found at L4. Ultrasound is a reliable method to observe the development of the conus level in young infants and to identify a tethered cord.