Comparative prenatal development of the spinal cord in normal and dysraphic dogs: embryonic stage.

The prenatal development of the canine spinal cord was examined by light microscopy in 8 normal embryos and compared with the development of the spinal cord in 10 embryos obtained by mating severely dysraphic Weimaraner dogs. Dysraphic lesions were found in 80% of the embryos examined from dysraphic matings. The primary lesion was aberrantly positioned mantle cells ventrad to the central canal in the floor plate area. In 30% of the embryos of this group, there was a division of the terminal neural tube. The dysraphic embryos had significantly shorter gray matter and spinal cord transverse diameters. This confirmed the observation that the mantle cells in the dysraphic specimens were less differentiated, being more compact and appearing more basophilic when hematoxylin and eosin stains were used.