Sinonasal cavities, inflammation

Acute sinusitis

This is usually due to bacterial superinfection following a viral upper respiratory tract infection. In the maxillary sinus, it can also arise from an infected tooth. The clinical symptoms are facial pain, nasal obstruction, purulent nasal discharge and postnasal drip. On conventional radiographs, acute sinusitis produces a soft tissue thickening following the contours of the sinus, reflecting mucosal and submucosal oedema. Such tissue thickening may also be seen in chronic or allergic sinusitis.

In acute sinusitis, fluid often collects in the sinus cavity, giving rise to an airfluid level head and neck; this makes the diagnosis of acute sinusitis much more likely, assuming that no other cause of an airfluid level is present (such as a recent sinus lavage or trauma). Airfluid levels can be better seen on CT than on conventional radiographs; they should be differentiated from a flat inflammatory polyp or mucous retention cyst. Extensive soft tissue thickening and outpouring of fluid will make the sinus appear completely opaque.

Complications of acute sinusitis are rare, and include:

- osteomyelitis: osteolysis of the bony sinus walls and eventually sequestration may be seen. This is most frequently seen in the frontal sinus.

- intracranial spread of infection: this is also most frequently seen with frontal sinusitis: the infection may spread through the posterior wall of the frontal sinus and result in an intracranial abscess.

- orbital complications: occur most frequently with ethmoid sinusitis. A subperiosteal phlegmon (and eventually abscess) may develop, with preseptal cellulitis. See abscess subperiosteal orbital. This may lead to intraorbital abscess formation, orbital thrombophlebitis, optic neuritis and occlusion of the central retinal artery.

Chronic sinusitis

This may rarely be caused by some specific chronic infections (such as tuberculosis), but usually follows an acute sinusitis. The symptoms are milder than in acute sinusitis; patients often complain of recurrent bouts of facial pain and headache. Radiographically, a soft tissue thickening following the contours of the sinusal walls is seen. The bony walls may appear thickened and show an increased density; this is caused by osteitis with bone deposition, leading to a smaller sinus cavity.

Allergic sinusitis

This is caused by an allergic inflammatory reaction in the upper respiratory tract to some antigen(s). Radiologically, it usually resembles infectious chronic sinusitis; overall, the soft tissue thickening has a more polypoid aspect, but this feature is not very specific. Also, see allergic sinusitis.

Fungal sinusitis

See fungal sinusitis.

RH