This is a contiguous series of CT slices showing the lumbosacral spine of a 7 month old infant. You can scan through the series either by (1) positioning the cursor over the image, holding down the left mouse button, then sliding the cursor up or down the image, or (2) hitting the keyboard keys < and > (no shift required). Scan through this series of CT slices and, starting at frame 37, try to identify the pathology indicated by the turquoise questionmark. A big hint is provided by the adjacent movie of a 3D reconstruction (called volume rendering) of these CTs. The answer will be revealed when you click on the drop-down arrow below the video.