I went through something similar and it was because my tubing wasn't working and so it wasn't draining the fluid completely. It was 20 years old and in fact it ripped when they pulled it out. I wasn't having a full-blown malfunction (vomiting, sunset eyes), just chronic headaches. The only test that DID prove it was a shunt problem was putting me on Diamox to reduce the amount of CSF (which made the headaches go away). Have they tried that? Good luck and keep us posted- the rest of us learn from these situations