Intracranial pressure during ventriculography using meglumine iothalamate.

A small increase in ventricular fluid pressure (1.3 +/- 0.3 mm Hg) occurs on isovolumetic addition of meglumine iothalamate to the lateral ventricle. A marked increase (46.3 +/- 3.2 mm Hg: P less than 0.001) in pressure occurs on passage of the contrast medium into the posterior part of the third ventricle; the aqueduct and the fourth ventricle. Theoretical mechanisms are discussed.