PSP is impaired in CF and DeltaF508 homozygosity is related to poor PSP. TBP is well preserved in the CF population and DeltaF508 homozygosity correlates with greater TBP, with the underlying mechanisms being unclear. Genotype might play a role in skull base pneumatization.

Objective (1) Compare paranasal sinus pneumatization (PSP) and temporal bone pneumatization (TBP) in cystic fibrosis (CF), chronic rhinosinusitis (CRS) and normal patients. (2) Determine impact of genotype and inflammatory mucosal disease on development of skull base pneumatization. Methods A case-control study using CF, CRS, and control patients from a tertiary rhinology clinic was conducted. TBP and PSP was assessed by computed tomography (CT) using a previously validated scale. Genotype data, including DF508 status, for CF patients was determined. Results 186 temporal bones and paranasal sinuses from 93 adult patients were assessed. Mean age 43.4 ± 14.9yrs. Inter-observer correlation for TB scoring was 0.86. TBP did not differ between CF, CRS, and normals (X2=6.93, p=0.38). PSP was significantly less in the CF group (X2=34.2, p<0.001). CRS and normals did not differ in PSP. 51.6% of CF patients were homozygous for DF508 and 16.1% were heterozygous. DF508 status was associated with poorer SP (X2=34.2, p<0.001) but greater TBP (X2=19.2, p=0.004). Conclusions PSP is significantly impaired in CF, and DF508 homozygosity is associated with poor development. Conversely, TBP is well preserved in the CF population, and DF508 homozygosity might even be related to enhanced TBP. Although this difference is striking, the underlying mechanisms are unclear. Genotype may play a significant role in the development of skull base pneumatization.