Overdrainage in a vp shunt

Hi, I was diagnosed a little over a year ago with a Psuedotumor Cerebri. So I don't know much about the symptoms of an over draining shunt or even if my shunt has malfunctioned. I have been having headaches again and they seem to get better when I lay down but I have also been having trouble with my vision, and I know that is sign that there is pressure build up. I went to the doctor last week and they are thinking about doing a pressure test which consists of putting a wire into my brain and leaving it there for 3 to 4 days, and that will let them know if I have too much pressure or not enough pressure. Has anyone ever had this done? If so could you possibly shine some light on it for me? Also I have a medium pressure valve, it is not a programmable shunt, I don't have much knowledge on what is better or if they are the same so if someone could please explain it to me that would be great!! I go back to the doctor Monday for a pre-op visit for the pressure test; maybe I will get some questions answered there!!!