MORPHOLOGICAL-STUDY OF EXPERIMENTAL SYRINGOMYELIA WITH KAOLIN-INDUCEDHYDROCEPHALUS IN A CANINE MODEL

In this morphological study the authors investigated whether spinal co rd cavitation, produced in young mongrel dogs that had been rendered h ydrocephalic by cisternal injection of kaolin, consists of a dilated c entral canal or intramedullary cavities. Hydrocephalus was noted in 50 of 56 dogs treated with kaolin. Of the 50 hydrocephalic young dogs, 2 9 were shown to have central canal dilation that was prominent at the thoracic level and 21 to have cervical intramedullary cavities in the posterior column and/or the posterior hem. In 11 dogs from the latter group these cavities were demonstrated to have no communication with t he central canal. This finding could not be explained by the hydrodyna mic theory. On histopathological examination, myelomalacia and hemorrh agic infarction following ventricular shunting were noted adjacent to the cervical cavities, which suggested vascular impairment. A perfusio n study revealed insufficient blood flow within the cervical cord at t he level of the intramedullary cavities. A close correlation between t he vascular insufficiency of the cervical cord and the pressure cone r esulting from significant hydrocephalus was observed. The latter may c ause cervicomedullary compression at the foramen magnum, affecting the venous drainage of the cervical cord below that level, resulting in i ntramedullary cavitation. Accordingly, vascular impairment was thought to play a significant role in the development of cervical syrinx form ation in our kaolin model. The current results may provide a reasonabl e explanation for the formation of noncommunicating cervical syringomy elia in Chiari I malformation.