Nasal Cavity: Paranasal Sinuses

10.1055/b-0034-87901

Nasal Cavity: Paranasal Sinuses

**Table 4.38 Small/absent sinuses**
Diagnosis	Findings	Comments
Congenital absence	Absence of frontal sinuses in 5% of population.
Cretinism	Delayed/decreased pneumatisation of sinuses.
Down syndrome	Absent frontal sinuses in 90%.
Kartegener syndrome	Absent frontal sinuses.
Fibrous dysplasia	Due to overgrowth of bony wall.
Hemolytic anemia Fig. 4.139, p. 382	Overgrowth of bony wall.
Postsurgery	Post Caldwell Luc operation.

**Fig. 4.139 Hemolytic anemia.** Coronal CT (bone window) shows expanded marrow cavities and diploic space causing a “hair-on-end” appearance and obliteration of sinuses in thalassemia.

**Table 4.39 Opacification of paranasal sinuses**
Diagnosis	Findings	Comments
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.
Trauma Fig. 4.140	Radiograph: soft-tissue swelling, maxillary sinus opacification, ± air-fluid level. CT: axial and coronal planes to visualize fracture.
Polyp/retention cyst	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.
Tooth bud	Radiograph: usually caused by projection and overlap. CT: shows true ectopic tooth bud within maxillary sinus.
Osteoma	Radiograph/CT: well-defined bony density. Mainly in frontal sinuses; rarely ethmoid and maxillary.	Assess for Gardner syndrome.
Mucocoele Fig. 4.141	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.
Primary malignancy Fig. 4.142a, b	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.
Metastases	CT: usually neuroblastoma and is associated with soft-tissue mass.
Juvenile angiofibroma	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.
Osteomyelitis	Radiograph/CT: sclerosis and destruction of sinus wall in setting of infection.	Usually frontal sinus.
Fibrous dysplasia Fig. 4.143	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.
Ossifying fibroma 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.