I go to pain management doctor that understands hydro pain. Something you may want to look into. Has your neurosurgeon done a shunt gram or a study to follow the flow with radio active die. This take about an hour and a half scan to do. Just to make sure you don't have protin building up at different times and causing a small block but when it lets up it probably passes. My vents don't ever change so a CT does nothing for me. A CT will show a build up of fluid but I woyuld thing you would have to have a big excess to see much difference.