Is pneumosinus dilatans an osteogenic disease that mimics the formation of a paranasal sinus?

Purpose Pneumosinus dilatans is a disease that produces an abnormal expansion of a paranasal sinus cavity, which contains only air and is lined by normal mucosa, and whose bony walls are displaced outwardly to cause facial embossing or intracranial, orbital or ethmoidal encroachment. Objective was to evaluate the hypothesis that pneumosinus dilatans is primarily an osteogenic disease. Methods A detailed clinical history of three consecutive patients with pneumosinus dilatans was taken. Each patient also underwent computed tomography (CT), fluorine-deoxyglucose positron emission tomography-CT (FDG PET-CT), fluorine 18-labeled sodium fluoride PET-CT (NaF PET-CT), and bone pathology. Results The FDG PET-CT and pathology confirmed that the mucosa inside the pneumosinus dilatans was normal and devoid of inflammatory cell infiltrate. Significant uptake of 18 F-NaF on PET-CT images correlated well with bone pathology, showing intense and diffuse bone remodeling. At a 1-year follow-up, following a frontotomy for case #1 and a middle antrostomy for case #2, there was a marked resolution of the patients’ clinical symptoms and deformities, new bone formation on the walls, stabilization of the new sinus shape and volume, and persistence of significant uptake of 18 F-NaF. Conclusions Pneumosinus dilatans is a rare disease. Its diagnosis is based on CT scan images. This study has shown that 18 F-NaF PET-CT and bone pathology are useful modalities for the positive diagnosis of difficult cases. Pneumosinus dilatans appears to be an osteogenic disease. Further research is needed to investigate a possible link between mechanisms involved in paranasal sinus formation and those involved in pneumosinus dilatans.