Relationship between intracranial and sagittal sinus pressure in normal and hydrocephalic dogs

The relationship between intracranial and sagittal sinus pressure in normal and kaolin-induced hydrocephalic greyhounds was examined. In normal dogs there was an average 14 mm Hg pressure difference between the ventricles and the sagittal sinus. Elevations of intraventricular pressure were accompanied by small but consistent elevations in sagittal sinus pressure. In hydrocephalic dogs the average pressure differential was only 2 mm Hg. Also elevations of intraventricular pressure were accompanied by greater elevations in sagittal sinus pressures than those seen in normal dogs. The volume-buffering capacity of the sagittal sinus was decreased, and sinography revealed filling of unusual venous collaterals in hydrocephalic dogs--both suggesting an increased resistance to outflow in the sagittal sinus.