Deep inside the human brain are cavernous regions known as the ventricles. They exist on each side (hemispheres) of the brain but all 4 are all interconnected..
Image of ventricular system
Peri (around) ventricular (ventricles).
Hypoattenuation denotes areas that are whiter and brighter than normal areas in a scan image. Usually this isn't a serious indication and may very well relate to normal aging processes.