Graph showing distance (mm) CSF in the pre-pontine cistern moved with deep inspiration and expiration. Each of the 10 volunteers was imaged on 3 occasions. Each point on the graph shows the average maximum distance with standard deviation. For the group as a whole, CSF in the pre-pontine subarachnoid space moved cephalad 16.5 ± 7.7 mm with inspiration and caudad 11.6 ± 3.0 with expiration. Average Maximum CSF movement during deep inspiration and expiration.