Changes in the CSF fluid pathways in the developing rat fetus with early onset hydrocephalus

Interest in the factors involved in the abnormal cortical development of the HTx rat fetus have led us to re-examine the structural and morphological changes in the CSF pathways preceding constriction and blockage of the cerebral aqueduct. Histological analysis was carried out on coronal and sagittal sections from HTx and Wistar fetuses. The aqueduct is found to be a broad channel extending from the posterior end of the third ventricle that ends in a blind pouch above the developing cerebellum. The aqueduct drains into the fourth ventricle via a vertically orientated, narrow channel lying between the posterior aspect of the pontine flexure and the anterior surface of the cerebellum. On Day E18 the connecting channel between the aqueduct and the fourth ventricle is blocked by apposition of its walls. 24 hours later the lateral ventricles begin to dilate and the anterior end of the aqueduct is blocked and the connecting channel between the aqueduct and the fourth ventricle reopens. The cause of these sequential changes in the CSF fluid pathways remains speculative.