Sqad/piggynose!! ... If you're seeing specialist excellent. But, from me practical experience. I thought I'd never had sinus problems ever. Cut short was investigated for possible TIA or CVST - Cerebral Venous sinus thrombosis. TIA's eliminated after bril. tests/scans etc. CVST - sort of eliminated, but thought to drain my sinuses via my temple!. Other suggestion was to drain them via dental treatment through a root canal.
Opted for the Dental line, great faith in my Dentist. Had it/them drained 27 times in 12 months!! I've been fine for 5 years, virtually no headaches at all. Official problem was re-diagnosed as "Migrainous Neuralgia". Don't confuse that with ordinary migraine, 'cos it's many years since i've had that! The final thought was that whatever I had it came from spending to much time at altitude, probably at/over 7,000ft. Again, I'm fine now, but don't chase Glaciers anymore!! Good luck; this is not meant to frighten you.