I first went to see an ent for my headache problems. My primare care physicaian assumed I was having recurrent sinus infections. After my sinuses showed up as clear on a ct scan, the ent sent me to a neurologist where I have been diagnosed as having migraines. The ent also prescribed oral and nasal meds to try to reduce the effects of rhinitis. He also told me that very few people with 'sinus' headaches are actually caused by sinsus -- they are migraines.
In the meantime, I have not responded to drug therapy for my nasal problems. The ent offered septoplasty as a remedy and said that 50% of people with migraines and septal problems get relief from migraines. Apparently, the nerve that causes migraines runs near the area of the nasal cavity, and the re-positioning can relieve pressure on that nerve.
But, he also cautioned that the surgery is likely to trigger a migraine just from the work that he has to do. I am willing to put up with one more migraine if I am more likely to not suffer them again!
Good luck to you!