Figure 4a. (a) Graph shows that total intracranial CSF volume increased resolutely across the life span included in the present study. (b) Nonetheless, graph shows that the percentage of CSF occupying intracranial remained at about 7%-9% during the period of rapid intracranial space and whole brain growth (Fig 1a, 1b) from early childhood to early adolescence. Thereafter, the percentage increased as whole brain volume declined, and intracranial space volume changed little. (On x axis, age scales change after 20-year point.)