The Surface Characteristics of Arachnoid Granulations

Abstract

The arachnoid granulations of six adult sheep were fixed by simultaneous subarachnoid and arterial perfusion with 3% glutaraldehyde in phosphate buffer. The pressure differences between the distal subarachnoid space and the superior sagittal sinus were maintained at O, 6.5, and 13 cm H₂O during fixation. The venous surfaces of the granulations were studied by scanning electron microscopy. As the pressure differences were increased, the following changes were seen in the apical areas of the granulations: the microvilli covering the endothelial cells decreased in number and size; the areas of apposition of adjacent endothelial cells were more irregular; the points of emergence of the endothelial-lined tubules became visible. These findings are consistent with previous ultrastructural studies.