Fig. 4.

a Preoperative axial CT scan demonstrating marked hydrocephalus with periventricular hypointensities suggesting increased intraventricular pressure. b, c Postoperative sagittal and axial T2-weighted MR images obtained 48 h after discontinued external ventricular drainage. Ventricular size is identical but periventricular hypointensities are less pronounced as on preoperative images. Note an obvious flow void between fourth ventricle and Blake’s pouch cyst (no third ventriculostomy performed)