The Space-Occupying Lesions

Abstract

Displacement begins when the brain yields locally to the pressure of the growing tumor (Fig. 1). As this happens, the adjacent portions of the ventricles are deformed and the reserve space of the neighboring cisterns and overlying sulci is used up and filled with brain tissue (Fig. 2). The shift of the brain often exceeds the confines of the cisterns and indents the corresponding portion of the opposite hemisphere (Figs. 21, 22). The local increase in pressure does not confine itself to the homolateral hemisphere but may be transmitted to the opposite hemisphere where possible, as by displacement of tissue between the edge of the falx and the base (Figs. 16, 22). Finally, pressure is transferred from the structures above the tentorium to those beneath it (axial displacement; Fig. 1), leading to herniation of the cerebellar tonsils into the foramen magnum (Figs. 42, 43).