OC01.04: Determination of the normal fetal conus medullaris level throughout pregnancy by a novel three-dimensional rendering technique

The aim of this study was to evaluate the level of the fetal conus medullaris (CM) throughout the pregnancy, by a simple 3D rendering technique. In this retrospective study we examined normal fetuses from uncomplicated pregnancies. In each fetus a mid-sagittal 3D rendering of the cervico-thoraco-lumbar spine was obtained. The ribs were counted in order to verify which vertebral body was adjacent to the distal rib (e.g. T12 if twelve ribs were present). In the A plane of the acquired volume, the reference point was placed on the tip of the CM. By applying 3D frame and highlighting the B plane, a line defining the conus level appears in the 3D render image (image 1a). The CM position was labelled according to the intersected vertebral body (e.g. L3), or to the space between two vertebrae (e.g. L3L4). We examined 1545 normal fetuses between 13 and 39 weeks of gestation. The assessment of the conus level was feasible in 96% of the fetuses scanned, in the remaining 4% high maternal body mass index or inappropriate fetal position prevented the clear visualisation of the CM. For each gestational week, we define the average, the lowest and the highest CM level observed. The results are presented in image 1b. This simple 3D technique enables a quick and accurate determination of the fetal CM level. Routine use of this method can aid in the prenatal diagnosis of tethered cord (closed spinal dysraphism) and may prevent postnatal irreversible neurologic damage. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.