What is the cause of headaches here?
The ventricles are dilated and there is transependymal CSF edema. These are features of hydrocephalus and the cause of the worsening headaches.
What type of hydrocephalus is demonstrated here? Why?
The lateral ventricles, and third and fourth ventricles are all dilated. On the T2 axial images, flow voids are demonstrated at the foramen of Monro, at the cerebral aqueduct, and also at the foramina of Luschka. Thus there is no obstruction to CSF flow through the ventricular system, making this non-obstructive (or communicating) hydrocephalus.
Widespread meningeal enhancement, particularly around the brainstem with nodularity. Nodular enhancement extends to the ventricular surface.
The lateral ventricles, third ventricle, and fourth ventricle are all dilated with transependymal CSF transudation.
Features here are of a diffuse process causing hydrocephalus at the level of the fourth ventricle.