Ventricular compliance in dogs with and without aqueductal obstruction

✓ In 10 dogs with stereotaxically-produced aqueductal blocks and in five dogs without aqueductal blocks, multiple small, equal volumes of Conray-60 were injected rapidly into one lateral ventricle while changes in the ventricular and cisterna magna pressure were recorded. In both groups of dogs the pressure rose exponentially with successive injections into the lateral ventricle. The rise was more rapid in the presence of an aqueductal block. These experiments give a measure of the response of the intracranial structures to increased pressure. Formulas are given to predict this response in animals with and without aqueductal obstruction under the conditions of the experiment. Findings are discussed in relation to the increase in ventricular size observed during fractional pneumoencephalography.