Radiology of the Third and Fourth Ventricles Part I

The radiography of the third ventricle has very clear and definite purposes, for it is the fact that alterations in its contour and in its position carry with them messages of the utmost value. It is the purpose of the present communication to illustrate, and, in a manner, to rationalise these alterations, and to emphasise the lessons which they convey. That internal hydrocephalus implies dilatation of the lateral ventricles has been known for centuries, but it was not until the remarkable work of Weed58 and Cushing,5 followed by that of Dandy,7 that a proper understanding was arrived at of the meaning of ventricular dilatation, and of its basis in obstruction to the outflow of the cerebro-spinal fluid. Twenty years ago the circulation of this fluid was for the first time beginning to be understood. Even at this day its meaning is not fully comprehended (Weed,59 1935). But although a full appreciation of every one of its physiological significances escapes us, yet the cruder facts concerning it are well enough known to be of great clinical service. It had long been recognised that cerebellar tumours were apt to be associated with dilatation of the ventricles above the posterior fossa, just as it had long been suspected that the choroid plexuses were the source of the cerebro-spinal fluid.