Fig. 3

Representative CSF flow rate vs. time over a cardiac cycle, showing the definitions of flow and pulsatility variables. Note that negative flow rates present during systole are in the craniocaudal direction. The pulse was monitored by a peripheral pulse unit applied to the first digit of the volunteer’s hand, and the local systolic flow peak occurs earlier at the vessels of the neck than at the first digit, explaining the location of the systolic peak in this figure. Time zero of the cardiac cycle in this figure represents the detected pulse peak at the finger