Hi ea333525,
Thank you for your question. I think we all wish there was a quick fix or a "miracle treatment" for migraine disease. Hopefully we'll see a cure in our lifetime.
Sinus pain, nasal congestion and drainage are often migraine attack symptoms. In fact most people who think they have a sinus infection are really having a migraine attack. You can read more about that here; https://migraine.com/blog/sinus-headache-or-migraine/.
Now on to SPG blocks used for pain relief. An allergy is possible, but I wonder if it's more migraine symptoms. I have a few articles about these you can read here; https://migraine.com/?s=SPG+nerve+block&submit=Go.
I understand how frustrating migraine disease is. I'm currently seeing my 5th true migraine expert and finally getting somewhere. If you haven't seen "true" migraine/headache expert, I would encourage you to seek one out. The thing is neurologists may be fine doctors, but have a hard time being experts in one area because they treat so many different conditions such as epilepsy, stroke, multiple sclerosis, Parkinson's and others. Migraine/headache are board certified in headache medicine, which is different than being certified in neurology. When you get a chance, take a look at this information on how these doctors are different and how to find one; http://migraine.com/blog/how-are-migraine-specialists-different/ and https://migraine.com/blog/really-find-headache-specialist/.
I hope this helps, keep me posted!
Nancy