Nasal Cavity: Paranasal Sinuses
Absence of frontal sinuses in 5% of population.
Delayed/decreased pneumatisation of sinuses.
Absent frontal sinuses in 90%.
Absent frontal sinuses.
Due to overgrowth of bony wall.
Fig. 4.139, p. 382
Overgrowth of bony wall.
Post Caldwell Luc operation.
Sinusitis—acute and chronic
Radiograph/CT/MRI: homogeneous opacification, mucosal swelling or air-fluid levels.
May see bony sclerosis or destruction if chronic.
CT important to assess for anatomic variations prior to functional endoscopic sinus surgery. Use low-dose coronal scans. Also useful to look for complications.
Radiograph: soft-tissue swelling, maxillary sinus opacification, ± air-fluid level.
CT: axial and coronal planes to visualize fracture.
Radiograph: Opacification of single maxillary antrum. Soft-tissue mass in anterior nasopharyx on lateral view.
CT: homogeneous soft-tissue masses with smooth margins, outlined by air (e.g., mucocoele).
Sequelae of sinonasal inflammation.
Radiograph: usually caused by projection and overlap.
CT: shows true ectopic tooth bud within maxillary sinus.
Radiograph/CT: well-defined bony density. Mainly in frontal sinuses; rarely ethmoid and maxillary.
Assess for Gardner syndrome.
CT/MRI: appearance varies with water and mucoid content. Shows peripheral enhancement, distinguishing it from neoplasm. Exhibits mass effect on adjacent structures and often expands into orbit.
Due to obstruction of sinus ostium. Most commonly frontal and ethmoid sinuses.
CT/MRI: MRI preferred due to superior soft-tissue contrast and to show intracranial extension. Need pre- and postcontrast studies.
Lymphoma, rhabdomyosarcoma, nasopharyngeal carcinoma, malignant histiocytoma.
CT: usually neuroblastoma and is associated with soft-tissue mass.
CT: isointense or low-density mass with widening of pterygopalatine fossa and bowing of posterolateral maxillary sinus. Marked CE.
MRI: T1 hypointense, T2 hyperintense with flow voids and avid enhancement. Can show cysts, cavitation, and hemorrhage.
Benign, most common in adolescent boys.
Radiograph/CT: sclerosis and destruction of sinus wall in setting of infection.
Usually frontal sinus.
CT: depends on fibrous vs. osseous component. Varies from radiolucent to ground-glass.
Unilocular/multilocular lesion, well-defined margin.
MRI: sharply demarcated mass, variable signal intensity, diffuse CE.
Fig. 4.114, p. 369
Fig. 4.138, p. 381
CT/MRI: expansile lesion with prominent areas of nonossified fibrous tissue.
Can be lytic, expansile containing calcification, and show cortical erosion.