**5. Chronic rhinosinusitis and complications**

An underlying odontogenic infection is reported to be the cause in up to 40% of chronic rhinosinusitis (CRS). In addition, several other conditions may mimic rhinosinusitis and challenge the radiological interpretation.

Five distinct radiological inflammatory patterns have been described, each with a different therapeutic course and surgical options [13], where the first three are caused by obstruction of the mucociliary flow. Obstruction of the maxillary sinus drainage is the most common. The level of obstruction is at the ostium and the thin ethmoid infundibulum and referred to as infundibular pattern. Obstruction of the middle meatus, the common drainage way for the frontal, anterior ethmoid, and maxillary sinuses, will cause obstruction of ipsilateral sinuses and is referred to as ostiomeatal (from ostium and meatus) complex (OMC) pattern. Less common is obstruction of the sphenoethmoidal recess that drains the posterior ethmoid and sphenoid sinuses. The two last patterns are sinonasal polyposis and incidental findings.

Surgical intervention of mucociliary obstruction is referred to as functional endoscopic sinus surgery (FESS). Functional refers to the widening of the natural ostia. For the infundibular and OMC inflammatory pattern, FESS includes uncinectomy (removing the uncinate process), opening the ethmoid infundibulum, and making a larger opening to the antrum (maxillary sinus) referred to as media-antrostomy.

#### **Figure 8.**

*(a) Coronal CT and (b) axial CT demonstrate a left-sided hypoplastic maxillary sinus with a retracted posterior fontanelle (lateral nasal wall) that mimic chronic rhinosinusitis. (c) On coronal MRI with T2 sequence, the sinus content is equal to mucus. There is no bowing of the sinus walls as typical for mucocele.*

#### **Figure 9.**

*(a) Coronal CT and (b) axial CT with bone algorithm and (b) with soft tissue algorithm demonstrate a pyocele (superinfected mucocele). (c) Coronal CT with soft tissue algorithm shows high attenuation more characteristic for a pyocele than a mucocele. (d) Coronal MRI T2 with fat suppression shows characteristic signal void of the pyocele. (e) Coronal MRI T1 with gadolinium shows contrast medium enhancement only in the peripheral mucosal lining.*

**17**

**7. Fungal sinusitis**

**Figure 10.**

acute, chronic, or granulomatous course [16].

*Imaging in Sinonasal Disorders*

mucus-filled sinus (**Figure 8c**).

to a mucocele (**Figure 9a**–**e**).

**6. Odontogenic sinusitis**

*DOI: http://dx.doi.org/10.5772/intechopen.90773*

Sometimes ethmoidectomy also is performed during FESS. Therefore, the course of

Complications to CRS are bone thickening (sclerosis, osteitis, neo-osteogenesis), demineralization and erosion of bone, and a negative sinus pressure that can cause infoldings of the sinus walls, referred to as silent sinus syndrome (**Figure 5b**),

Hypoplastic maxillary sinus with retracted posterior fontanelle (**Figure 8a**–**c**) may mimic silent sinus syndrome but usually has no clinical impact despite the

In addition, retracted posterior fontanelle should not be confused with a mucocele that remodels and expands the sinus. A bacterial superinfection of a mucocele will result in a pyocele. A pyocele has characteristic CT and MR findings compared

Odontogenic sinusitis should be suspected when maxillary sinusitis does not heal [14, 15]. This is especially in the case of unilateral CRS (**Figure 10a** and **b**), but odontogenic infection may also be the source of bilateral CRS. Before referring to FESS, due to maxillary sinus opacification, odontogenic maxillary sinusitis must be ruled out. FESS in odontogenic cases may induce more inflammation and osteitis [1]. Odontogenic sinusitis and sinonasal complications of dental disease or treatment represent a hetero-

Fungal sinusitis can be noninvasive, which includes fungus ball (mycetoma) (**Figure 11a**–**c**) and allergic fungal sinusitis (**Figure 12a**–**d**), or invasive with an

*(a) Coronal CT and (b) axial CT reveal periapical lucency around a molar tooth [16] consistent with odontogenic* 

*infection as the cause of sinusitis. The sclerotic maxillary sinus walls indicate a long-standing infection.*

Invasive fungal sinusitis is most common in immunocompromised patients.

Invasive fungal sinusitis is revealed by fungal deposits outside the sinus walls that obliterate the fat plane. The sinus wall usually is sclerotic and intact, and the spread of fungus is by the vessels through the bone (**Figure 13a**–**d**). Demineralization and erosion of the lateral nasal wall is usually seen when the maxillary sinus is involved.

geneous group of conditions that often require multidisciplinary care [17].

the anterior ethmoid artery should be included in the radiological report.

which may result in larger orbit and cause enophthalmos and diplopia.

#### *Imaging in Sinonasal Disorders DOI: http://dx.doi.org/10.5772/intechopen.90773*

*Sino-Nasal and Olfactory System Disorders*

**16**

**Figure 9.**

**Figure 8.**

*the peripheral mucosal lining.*

*(a) Coronal CT and (b) axial CT with bone algorithm and (b) with soft tissue algorithm demonstrate a pyocele (superinfected mucocele). (c) Coronal CT with soft tissue algorithm shows high attenuation more characteristic for a pyocele than a mucocele. (d) Coronal MRI T2 with fat suppression shows characteristic signal void of the pyocele. (e) Coronal MRI T1 with gadolinium shows contrast medium enhancement only in* 

*(a) Coronal CT and (b) axial CT demonstrate a left-sided hypoplastic maxillary sinus with a retracted posterior fontanelle (lateral nasal wall) that mimic chronic rhinosinusitis. (c) On coronal MRI with T2 sequence, the sinus content is equal to mucus. There is no bowing of the sinus walls as typical for mucocele.* Sometimes ethmoidectomy also is performed during FESS. Therefore, the course of the anterior ethmoid artery should be included in the radiological report.

Complications to CRS are bone thickening (sclerosis, osteitis, neo-osteogenesis), demineralization and erosion of bone, and a negative sinus pressure that can cause infoldings of the sinus walls, referred to as silent sinus syndrome (**Figure 5b**), which may result in larger orbit and cause enophthalmos and diplopia.

Hypoplastic maxillary sinus with retracted posterior fontanelle (**Figure 8a**–**c**) may mimic silent sinus syndrome but usually has no clinical impact despite the mucus-filled sinus (**Figure 8c**).

In addition, retracted posterior fontanelle should not be confused with a mucocele that remodels and expands the sinus. A bacterial superinfection of a mucocele will result in a pyocele. A pyocele has characteristic CT and MR findings compared to a mucocele (**Figure 9a**–**e**).
