Histological examination of kaolin-induced hydrocephalus

✓ To determine the possible efficacy of distal subarachnoid space shunting in the treatment of hydrocephalus, the brains of dogs with kaolin-induced hydrocephalus were examined histologically to discover the location of the kaolin and the nature of any biological reaction to the foreign substance. Hydrocephalus was produced by the mechanical infusion of a sterile kaolin suspension into the cisterna magna. After sacrifice the brains were removed and sectioned at the upper cervical cord, pontomedullary junction, midbrain, and optic chiasm, then histologically studied and photographed. Kaolin deposition was most notably found ventral to the brain stem, approaching the foramen of Luschka, up to and within the third ventricle. Ventrally, the kaolin and subsequent inflammatory reaction extended from the chiasmatic cistern down throughout the pre-pontine cistern to surround the cervical cord. In these cases, the kaolin was not found in the lateral ventricles, nor did it extend above the basal and ambient cisterns to cause inflammation in the cortical subarachnoid spaces. Due to the failure of the kaolin and any accompanying reaction to reach the cerebral convexities, it can be concluded that these distal spaces are potentially functional and open to cerebrospinal fluid (CSF) flow and absorption. The pathophysiology of kaolin-induced hydrocephalus is then due to the inflammatory obstruction of the CSF pathways, preventing normal bulk CSF flow to the distal subarachnoid spaces of the cerebral hemispheres thus mimicking some forms of human hydrocephalus.