In each of these cases of obstruction, the crucial detail is that the brain never stops producing CSF. So any restriction of outflow or failure to remove accumulating fluid means the ventricles grow steadily larger, like a balloon being inflated inside a jar. Because the skull (i.e., the jar) is rigid, brain cells get compressed between the growing ventricles and the stiff bone. As the ventricles continue to enlarge, the pressure on those trapped brain cells grows more and more intense. It can even reach a point where the cells can be seriously damaged. One way to stop this damaging CSF buildup is to create a new pathway out of the skull by placing a drain called a ventriculostomy.