Anesthesia causing headaches?

Okay, I am not a CRNA nor will likely ever be, but I thought you all could help me with a situation with one of our patients.

20-year-old chronically ill, had a routine (for them) surgery; since has had intractable headaches and has progressed with pain meds until they are on a PCA morphine pump and still rating pain 7-8 most of the time, at least 2 weeks later. LP and head CT were negative. Patient does not seem to be "making up" pain; is usually pretty functional despite illness but can't seem to improve after this surgery. Can anesthesia of some kinds cause headaches like this and if so, is there anything we can do about it that will be effective? (I am not sure if I would have the authority since I am just a staff nurse caring for the patient, but wondering if this is even a possible cause??)