Fig. 2

Diagrams of intermittent and continuous CSF drainage. In continuous CSF drainage (A), the drained CSF volume is measured every 8 h (↑). The approximate CSF drainage volume of 150 mL per day is modified by the height of the disk open to atmospheric pressure; if the CSF drainage volume within 8 h is < 40 mL, the disk is lowered by 2 cm; if the CSF drainage volume is > 60 mL, the disk is raised by 1 cm. In intermittent CSF drainage (B), CSF is drained three times a day, with 50 mL of CSF drained per session; disk is clamped when 50 mL of CSF is drained, and it remains clamped until the next session. If 50 mL of CSF is not drained after 4 h of opening, the height of the disk is adjusted (lowered by 2 cm), and it is clamped until the next session