I would try a second opinion myself.

Bailey gets sinus attacks, which in no way mimick a human sinus attack.
My vet didn't know what to say except, "Must be a food allergy", which is what most vet's comments are when they don't have a definitive answer, they say to change the food. She observed him in her office for about 5 hours nothing....yep, change the food.....no I didnt' change the food because I KNEW it wasn't his food. So, I take him to another vet and LO and BEHOLD.........I tell the vet the symptoms, he looks him over,the vet looks at me without blinking an eye and he says, "he's got a sinus infection". I say, "oh, you've seen this before?", the vet says, "sure have, a lot of dogs and other animals in this valley get this and I see this very often." He gave Bailey a shot, gave 2 prescriptions and we were all set and on our way. Now, when I see the symptoms appearing I give him his medicine and he's good to go. BTW, his meds are over the counter human meds. From Bailey's symptoms I would never have guessed that it was sinus related. Bailey's regular vet was not in agreement when she got the report from the other vet but I can tell you what........Bailey hasn't had another occurrance since May or June and we are now in a big sinus infection season here because of our unusually warm fall/winter (more like early Spring weather).
Please get another opinion.