The Rate of Cerebrospinal Fluid Formation Proximal and Distal to Aqueductal Obstruction in the Dog

The authors describe a stereotactic technique for producing aqueductal obstruction in dogs. Cerebrospinal fluid was collected proximal and distal to the occluded aqueduct for three hours. The choroid plexuses from all four ventricles were weighed. Each lateral ventricle plexus comprised approximately 18% of the total; the plexus of the third ventricle was 25.3%, and that of the fourth ventricle was 38.2%. The rate of fluid formation was not related to the weight of the choroid plexus, suggesting either (a) significant extrachoroidal sources of cerebrospinal fluid or (b) a functional difference between the choroid plexus of the fourth ventricle and those proximal to the aqueduct.