Pathogenesis of aqueductal occlusion in congenital murine hydrocephalus

Abstract

In a study of congenital hydrocephalus in the murine mutant (hy-3/hy-3), aqueductal stenosis developed during the progression of hydrocephalus. In stage 1 hydrocephalus (ventricular dilation and open aqueduct) a block in the subarachnoid space over the cerebral convexities caused the lateral and 3rd ventricles to enlarge. The ependyma became stretched, and a collection of edematous fluid formed in the subependymal layer. In stage 2 hydrocephalus (edema in white matter around lateral ventricles and compression of quadrigeminal plate) edema developed peripheral to ependyma in the aqueduct and compressed the lateral surfaces of the aqueductal wall to obstruct the lumen. While periaqueductal edema was spreading, the forces of the expanding midline structures and the cystic occipital horns altered the relationship of brain structures. There was no proliferation of glia, but instead a simple stenosis which resulted from a combination of ventricular dilation, cerebral edema, brain shift, brain-stem compression and brain-stem edema. Normal ependymal specializations were observed that indicate a more active functional role for aqueductal ependyma than previously recognized.