**Abstract**

Computed tomography (CT) is the "working horse" in sinonasal imaging and should always be the first choice. Magnetic resonance imaging (MRI) is complementary to CT when complications to rhinosinusitis or neoplasm are suspected. Imaging of the paranasal sinuses is common due to stuffy nose. In order to correct interpretation, proper imaging technique as well as knowledge of bony anatomy and variants and mucosal incidental findings are of outmost importance. Acute rhinosinusitis is very common and does not need imaging unless complications are suspected. In chronic rhinosinusitis, a CT examination is needed to find the cause and site of the mucociliary obstruction and to rule out other causes as odontogenic and fungal sinusitis and neoplasms.

**Keywords:** paranasal sinuses, computed tomography, magnetic resonance imaging, retention cysts, polyps, mucocele, pyocele, rhinosinusitis, odontogenic sinusitis, fungal sinusitis, neoplasms, systemic diseases

## **1. Introduction**

Computed tomography (CT) is the "working horse" in sinonasal imaging and should always be the first choice. Magnetic resonance imaging (MRI) is complementary to CT when complications to rhinosinusitis or neoplasm are suspected.

Imaging of the paranasal sinuses is common due to stuffy nose. In order to correct interpretation, proper imaging technique as well as knowledge of bony anatomy and variants and mucosal incidental findings are of outmost importance.

Imaging should be performed when the stuffy nose and rhinosinusitis do not heal despite medical therapy. Acute rhinosinusitis (ARS) is usually self-limiting, and imaging is only indicated when complications are suspected.

In chronic rhinosinusitis, a CT examination is needed to find the cause and site of the mucociliary obstruction and to rule out other causes as odontogenic and fungal sinusitis and neoplasms.
