Temporal bone pneumatization and its relationship to paranasal sinus development in cystic fibrosis* Clarice M. Seifert 1 , Richard J. Harvey 2 , Joe W. Mathews 1 , Ted A. Meyer 1 , Chadwick Ahn 1 , Brad A. Woodworth 3 , Rodney J. Schlosser 1 1 Department of Otolaryngology - Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, USA 2 Department of Otolaryngology - Skull Base Surgery, St Vincent’s Hospital, Darlinghurst, Sydney, Australia 3 Department of Otolaryngology - Head and Neck Surgery, University of Alabama Birmingham, Alabama, USA *Received for publication: 2008; accepted: November 13, 2009 DOI:10.4193/Rhin09.145 INTRODUCTION Cystic fibrosis (CF) is an autosomal recessive disease (1) affect- ing more than 30,000 individuals in the United States and most commonly affecting the Caucasian population (1 in 3200 live births) (2) . It is caused by defects in the gene found on chromo- some 7 that encodes the cystic fibrosis transmembrane con- ductance regulator (CFTR) protein, a protein responsible for transport of chloride and other electrolytes across the cell membranes of epithelial cells. Defects in this protein results in the production of abnormally thick mucus by exocrine glands, with complications affecting many organs including the lungs, bile ducts, pancreas, paranasal sinuses, intestines, and male reproductive tracts (2,3) . More than 1500 mutations have been associated with CF to date (4) . The most common mutation, ΔF508, accounts for approximately 66% of the CFTR mutations (4) . This mutation results from the deletion of three base pairs encoding for a phenylalanine at the 508 position in the protein, with resultant misfolding of the protein. The improper folding of the proteins results in defective trafficking: the protein is not transported to the membrane and is subsequently degraded (5) . Paranasal sinus disease in CF patients is well described, likely resulting from a combination of impaired mucociliary clear- ance, increased viscosity of the mucus with stasis, promotion Background: There is significant debate on the influence of inflammatory mucosal disease on paranasal sinus pneumatization (PSP) and temporal bone pneumatization (TBP) in cystic fibrosis patients (CF). It is often assumed that mucosal disease of the paranasal sinuses will negatively influence development and pneumotization of the paranasal sinuses and temporal bone system. Methods: A case-control study of TBP and PSP in CF, chronic rhinosinusitis (CRS) and healthy control patients from a tertiary rhinology clinic. TBP and PSP were assessed by com- puted tomography (CT) using a previously validated scale. Genotype data for patients with CF was determined. Results: In total, 186 temporal bones and paranasal sinuses from 93 adult patients were assessed through evaluation of CT scans. Tha patients had a mean age of 43.4 ± 14.9 yrs. The interobserver correlation for TB scoring was 0.86. TBP did not differ between CF, CRS and con- trols (χ 2 = 6.93, p = 0.38). PSP was less in the CF group (χ 2 = 34.2, p < 0.001) than the CRS and control groups. CRS and controls did not differ in PSP. 51.6% of CF patients were homozy- gous for ΔF508 and 16.1% were heterozygous. The ΔF508 status correlated with poorer SP (χ 2 = 34.2, p < 0.001), but greater TBP (χ 2 = 14.9, p = 0.002). Conclusions: PSP is impaired in CF and ΔF508 homozygosity is related to poor PSP. TBP is well preserved in the CF population and ΔF508 homozygosity correlates with greater TBP, with the underlying mechanisms being unclear. Genotype might play a role in skull base pneumati- zation. Key words: pneumotization, temporal bone, mastoid, paranasal sinus, genotype, chronic otitis, cystic fibrosis SUMMARY ORIGINAL CONTRIBUTION Rhinology, 48, 233-238, 2010