Frontal sinus disease. IV. Cellular response to experimentally-induced infection.

The pathogenesis of chronic frontal sinusitis is poorly understood. The canine frontal sinus model was developed to isolate experimentally the variables involved. We have recently determined that blockage of the naso-frontal duct does not, by itself, produce sinusitis or mucocele experimentally. The purpose of the present investigation is to examine the histological and ultrastructural responses of the sinus mucosa to artificially-induced infection. Bone wax was implanted in the canine frontal sinus via an osteoplastic flap, and subsequently removed three months later. Radiological, histological and ultrastructural analysis of the resultant infected mucosa was performed at periods up to one year. The sinus mucosa did not return to normal up to nine months following removal of the infection-inciting foreign body. Persistent changes included epithelial and submucosal thickening, polypoid degeneration, matting of the ciliary carpet, and "bursting" of the ciliary cell bodies. In the light of this and previous experiments, an insidious cycle of events leading to irreversible frontal sinus disease is postulated, requiring the interplay of at least three variables: the infectious insults, the response of the sinus mucosa, and the variable patency of the nasofrontal duct.