Histological and MRI study on experimental syringomyelia

To clarify the pathogenesis of syringomyelia, we examined MRI and histological changes in experimental syringomyelia in progress. Syringomyelia was induced in 19 rabbits by intracisternal injection of a kaolin solution. MRI was performed at 3, 7, 14, or 21 days after the injection. The rabbits were killed immediately after the last MRI and histological examinations were then performed. MRI showed two types of syrinx: hydromyelia accompanied by ventriculomegaly, and cervical cord cavitation in the posterior horn without ventriculomegaly. All changes observed on MRI findings were verified by histological examination. The first type of syrinx had enlarged central canals that were lined with ependyma, but there was no marked presence of spongy tissue around the central canal. The obex was completely filled with kaolin solution. The second type featured small central canals and sponginess or cavities of gray matter in the upper or middle spinal cords. Kaolin was observed around the obex but it was not completely filled. Fourteen days after kaolin injection, the shapes of syrinxes had remained almost the same. MRI showed the chronological changes very clearly, and histological differences of the syrinx correlated with the degree to which the obex was filled with kaolin.