Sinusitis can definitely by associated with AS. For the longest time I complained to my GP that my ears hurt. He would give me a round of antibiotics or ear drops at times. The medication offered only temporary relief and my ears continued to ache. It was not until I had gone to the UT Dental school, for a dental implant in my upper jaw, that I found out that I had a sinus infection. Before they started my implant the dental school performed a CT scan and discovered that I had an obstruction in my sinus cavity. I was instructed to see an Ear Nose and Throat Dr.(ENT) My ENT did another CT scan and found a severe obstruction and made an appointment for me to have a sinus operation to help me drain my sinus cavity. My ENT said I had a bacterial infection. After the 1.5 hour in office operation, I quickly realized my ears did not heart as much. For the last 14 months I have been rinsing my sinuses at least 3 times a day with a saline solution and sometimes I add an antibiotic to the saline solution. I still have a bit of the infection, but it appears to be going away. I do have AS and I am HLA-B27 positive. I have been on Carol Sinclair's Low Starch Diet for around 8 or 9 months and her diet is working.
If you have concerns that you have sinusitis, see an ENT and get evaluated.