Anorectal anomaly: neuropathological changes in the sacral spinal cord

The study was carried out on the bodies of five full-term newborn babies and 10 newborn patients with anorectal anomalies (four of whom had the high deformity, one had the intermediate, and five had the low). Serial transverse sections of the sacral spinal cords at 30 microns were made and stained with Nissle's. It was found that in the medial column of the sacral spinal cord there were two groups of motoneurons: posteriomedian group (group A) and anteriomedian group (group B). The former was found mainly in S3 and S4 and the latter extended from caudal S4 to caudal S2. In six of the 10 deformitive cases the cross-sections of the S5 showed a large diamond-shaped central canal and a thin conus medulla which could be distinguished as the basal and alar laminae; in one case, the lower part of the central canal and the anterior median fissure appeared undeveloped; in one case, the lower part of the central canal was divided into two large canals by a sagittal septum; and in the other two cases, their central canals appeared widened and flattened. Additionally, the average numbers of motoneurons in the group B of the high or intermediate deformity and the low deformity were 13.4% and 61.1%, respectively, of the normal number, and the corresponding numbers of group A were 61.3% and 77.7%, respectively, of the normal number. The observations suggest that sacral myelodysplasia is one of the neuropathological features in anorectal anomaly and may be responsible for the pathological changes in its peripheral nerve system.