Contact your neurosurgeon regarding this PRIOR to your sugery. Do not start any new medications (even over the counter) this close to your surgery date without talking with your doctor. It may just be stress, but all it takes is a phone call to your doctor to determine this.
oh forgot to say IBS issues can cause nausea..and stress can flare IBS issues..no doubt you're stressed as well.. so fiber supplements and water..(starting slowly) might also be causing nausea..my guess is your tummy though.
yeah I would totally tell them ahead of time..
I've been told that sometimes when patients (now this is just from what i've heard...) is when they go through a surgery or some tramatic thing happens sometimes you can develop an almost silent ulcer which would bring on waves of nausea at times. I would just inform the surgeon and ask if it's ok to go buy some prilosec at the store to try or maybe he can give you a week of nexium or some acid blocker OR just wait until after the surgery to take nexium. You could try tums or pepto bismal the next time you get hit with a nausea wave and see if it subsides. Also anxiety attacks or panick attacks can bring on nausea buuut..ee.. either way it wouldn't hurt to do a few weeks of nexium honestly if that's what it is. But yeah my personal opinion, I think that surgeon would want to know if you're having some problems before surgery just to be safe.
Good luck on the surgery :S