Abstract

Intraventricular pressure was studied in 12 patients undergoing ventriculography with a water soluble positive contrast medium. Isovolumetric instillation of meglumine iothalamate into the lateral ventricles and the anterior part of the third ventricle caused only a small increase in ventricular fluid pressure (1.3 +/- 0.3 mmHg), but the pressure increased markedly (46.3 +/- 3.7 mmHg; P less than 0.001) when the contrast medium entered the posterior end of the third ventricle, aqueduct of Sylvius,, and fourth ventricle. This sharp increase in intracranial pressure could not be attributed solely to the postural changes or to alterations in arterial blood pressure. Possible mechanisms are discussed.