Definitely. There are stories of patients who had balloon sinuplasty and then developed a strange smell in their sinuses that wouldn't go away. They also had a constant discharge that was both embarrassing and a sign that something was seriously wrong. It seems the procedure had disrupted the normal balance in their sinuses in a very negative way.
Sure. I've heard of a story where a person had balloon sinuplasty, and shortly after, they started having intense facial pain. It turned out that there was some nerve damage during the procedure, which was not anticipated. The pain was so bad that it affected their daily activities and mental well - being for a long time.
Yes. There was a case where a patient's sinus condition deteriorated rapidly after balloon sinuplasty. The procedure seemed to trigger an overgrowth of bacteria in the sinuses, leading to a very severe and resistant sinus infection that took months to treat. It was a nightmare for the patient.