My suspicion is that there is still a problem with the ears. It is possible that the punctured eardrum led to an infection, or that the infection on the eardrum actually is much deeper. More likely, though, is that the changes relate to the polyp. While it is possible that some damage occurred during the surgery, it is more likely that the damage is due to scar tissue, or that the polyp was cancerous and whatever was not removed is growing and putting pressure on the brain. Was the polyp sent for a biopsy?