CT - Hydrocephalus: A 31 year old woman with moderate mental retardation status post ventriculo-peritoneal shunting at age 3 presented with worsening headache. This head CT scan without contrast reveals chronic hydrocephalus due to aqueductal stenosis with marked dilatation of both lateral ventricles, especially the frontal horns, and the midline third ventricle. The high attenuation marking in the left occipital horn is a portion of the ventricular catheter.