Mary, I bet you are probably exactly right that something is going on with Coco Puff. You know him better than anybody. I had to bring Tiger in a few times before the vets would believe me that his purring was deeper and rumbly. We know when they aren't right.

I found a link that has info on people but I would guess that it would be similar with animals too. It talks about how sinusitis can lead to middle ear infections and/or temporary deafness. The site suggests that steaming and hot compressing on the face (above and beyond the meds) might relieve the pressure.
Prayers that this is a temporary condition and that your VERY handsome Coco Puff will be saying 'Raaaooouuuullll' to you soon!!

link