Actually, if the opening pressure is too high, it could mean a diagnosis of Psuedo Tumor Cerebri.

This is specifically why I had my LP. The neuro was pretty sure I had it.

They knew immediately that this wasn't my problem, as my pressure was normal.

I don't remember what he scale is, but a pressure of 15 doesn't seem high. If I remember correctly, the neuro was expecting a pressure in the 100's if I had PTC (but I could be remembering incorrectly).

I suggest you ask your doctor to explain.