Calvarial thickening from chronic ventricular shunting
The skull is thought to develop partly in response to the pressure applied to it. It has been suggested that pressure changes to the dura mater actually mediate the change in calvarial development.
In hydrocephalus, the calvarial bones can become thinned due to the abnormally high pressure applied to them. With chronic shunting, however, the process is reversed, and chronic low intracranial pressures can result in a thicker skull than normal.
A thickened calvarial vault with chronic shunting has been termed “hyperostosis cranii ex vacuo.”