**2.4 Anatomical variations**

Variation in anatomy is a rule than an exception. Nature has customised different anatomies for every individual. Therefore, one must be aware of these possible variations before any surgical interventions. The major consequences of these anatomical variations are narrowing of the infundibulum.

Air in the nose and PNS act as natural contrast, so CT scan in bone and soft tissue windows is sufficient to diagnose anatomical variations and pathology in most of the cases of chronic rhinosinusitis (CRS). Here, a brief account of radiological images of anatomical variations and corresponding nasal endoscopic findings is discussed.

• DNS

It is the commonest anatomical variation. Deviation of posterior nasal septum causes CRS by creating pressure and air flow changes within the maxillary sinuses [6] (**Figures 1** and **2**). Septal spur causes turbulence in airflow leading to polyp formation.

• Concha bullosa

It is pneumatisation of middle turbinate involving its inferior bullous portion, and it may be bilateral [7, 8]. Large concha causes significant obstruction of nose. Such patients present with sinogenic headaches or chronic sinusitis. Sometimes there can be pneumatisation of lamina of middle turbinate known as lamellar concha.

**Figure 1.** *CT showing sharp spur impinging middle turbinate.*

**Figure 2.** *Endoscopic picture showing spur impacting middle turbinate in left nasal cavity.*

A paradoxical bent of middle turbinate is defined as turbinate having convexity towards the lateral nasal wall. This leads to narrowing of infundibulum [9–11] (**Figures 3** and **4**).


Can be medially bent uncinate process (**Figures 6** and **7**) or pneumatised uncinate process (**Figures 8** and **9**). Sometimes the uncinate can protrude anterior-inferior to middle turbinate, giving the impression of two middle turbinates [12].

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• Big agar

**Figure 5.**

**Figure 4.**

titis (**Figures 10** and **11**).

*CT PNS coronal cuts showing pneumatisation of superior turbinate.*

Agar cells are usually pneumatised from the frontal recess. Extensively pneumatised agger nasi cells will narrow the frontal sinus drainage pathway leading to frontal sinusitis [13]. Agger nasi cells are closely related to lacrimal sac and are separated from the latter by thin lacrimal bone. This bone may also be naturally dehiscent leading to spread of infection and subsequent dacryocys-

*Rhinosinusitis: How Common Are Anatomical Variations Responsible?*

*CT PNS showing bilateral paradoxical middle turbinate with right lamellar concha.*

*DOI: http://dx.doi.org/10.5772/intechopen.83689*

**Figure 3.** *CT PNS showing bilateral concha bullosa.*

*Rhinosinusitis: How Common Are Anatomical Variations Responsible? DOI: http://dx.doi.org/10.5772/intechopen.83689*

*Rhinosinusitis*

(**Figures 3** and **4**).

**Figure 2.**

• Uncinate process

turbinates [12].

A paradoxical bent of middle turbinate is defined as turbinate having convexity towards the lateral nasal wall. This leads to narrowing of infundibulum [9–11]

Can be medially bent uncinate process (**Figures 6** and **7**) or pneumatised uncinate process (**Figures 8** and **9**). Sometimes the uncinate can protrude anterior-inferior to middle turbinate, giving the impression of two middle

• Pneumatisation of superior turbinate- (**Figure 5**)

*Endoscopic picture showing spur impacting middle turbinate in left nasal cavity.*

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**Figure 3.**

*CT PNS showing bilateral concha bullosa.*

**Figure 4.** *CT PNS showing bilateral paradoxical middle turbinate with right lamellar concha.*

**Figure 5.** *CT PNS coronal cuts showing pneumatisation of superior turbinate.*

• Big agar

Agar cells are usually pneumatised from the frontal recess. Extensively pneumatised agger nasi cells will narrow the frontal sinus drainage pathway leading to frontal sinusitis [13]. Agger nasi cells are closely related to lacrimal sac and are separated from the latter by thin lacrimal bone. This bone may also be naturally dehiscent leading to spread of infection and subsequent dacryocystitis (**Figures 10** and **11**).

#### *Rhinosinusitis*

**Figure 6.** *DNE showing medially bent uncinate process.*

**Figure 7.** *CT showing thick and medially bent uncinate process.*

• Haller cell

The presence of infraorbital ethmoidal cells can obstruct the drainage pathway of the maxillary sinus and also increase the risk of orbital injury during ethmoidectomy (**Figure 12**).

• Onodi cell

It is insinuation of posterior ethmoid air cell between optic nerve and sphenoid sinus. It is associated with increased risk of injury with optic nerve or carotid artery during functional endoscopic sinus surgery (FESS) [14] (**Figure 13**).

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**Figure 9.**

**Figure 8.**

• Accessory ostia

*Endoscopy showing pneumatised uncinate process.*

recirculation and CRS [15] (**Figures 14** and **15**).

Maxillary sinus drains through the natural ostia and the presence of accessory ostia does not play a role in its physiologic drainage. Rather, it leads to mucous

*Rhinosinusitis: How Common Are Anatomical Variations Responsible?*

*DOI: http://dx.doi.org/10.5772/intechopen.83689*

*CT showing pneumatised uncinate process on left side.*

*Rhinosinusitis: How Common Are Anatomical Variations Responsible? DOI: http://dx.doi.org/10.5772/intechopen.83689*

*Rhinosinusitis*

**Figure 6.**

*DNE showing medially bent uncinate process.*

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• Haller cell

**Figure 7.**

• Onodi cell

ectomy (**Figure 12**).

*CT showing thick and medially bent uncinate process.*

The presence of infraorbital ethmoidal cells can obstruct the drainage pathway of the maxillary sinus and also increase the risk of orbital injury during ethmoid-

It is insinuation of posterior ethmoid air cell between optic nerve and sphenoid sinus. It is associated with increased risk of injury with optic nerve or carotid artery during functional endoscopic sinus surgery (FESS) [14] (**Figure 13**).

**Figure 8.** *CT showing pneumatised uncinate process on left side.*

**Figure 9.** *Endoscopy showing pneumatised uncinate process.*

• Accessory ostia

Maxillary sinus drains through the natural ostia and the presence of accessory ostia does not play a role in its physiologic drainage. Rather, it leads to mucous recirculation and CRS [15] (**Figures 14** and **15**).

**Figure 10.** *CT PNS showing big agar on left side. Note that frontal sinuses are still clear.*

**Figure 11.** *CT PNS showing infected agar on right side with haziness in right frontal sinus.*

• Hypoplasia/agenesis of maxillary sinus

According to Bolger and Parsons, maxillary sinus hypoplasia can be classified into three types:

Type I—There is mild decrease in maxillary sinus volume with normal uncinate and normal ethmoid infundibulum.

Type II—There is mild-to-moderate reduction in volume of maxillary sinus combined with CT evidence of an absent or hypoplastic uncinate process and an absent or poorly defined ethmoid infundibulum due to uncinate process being fused with the inferomedial wall of the orbit.

Type III—Maxillary sinus is primarily absent. Ethmoid infundibulum and uncinate process are absent [16].

In our case, there was type III maxillary sinus hypoplasia (**Figures 16** and **17**).

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**Figure 14.**

**Figure 12.**

**Figure 13.**

*Coronal section of PNS showing bilateral Onodi cell.*

*Rhinosinusitis: How Common Are Anatomical Variations Responsible?*

*CT PNS showing Haller cell on left side with narrowing of infundibulum. Sinuses are still clear.*

*CT PNS showing accessory ostia on right with clear maxillary. On the contrary, opposite sinus is hazy.*

*DOI: http://dx.doi.org/10.5772/intechopen.83689*

*Rhinosinusitis: How Common Are Anatomical Variations Responsible? DOI: http://dx.doi.org/10.5772/intechopen.83689*

*Rhinosinusitis*

**Figure 10.**

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into three types:

**Figure 11.**

• Hypoplasia/agenesis of maxillary sinus

*CT PNS showing infected agar on right side with haziness in right frontal sinus.*

*CT PNS showing big agar on left side. Note that frontal sinuses are still clear.*

nate and normal ethmoid infundibulum.

fused with the inferomedial wall of the orbit.

uncinate process are absent [16].

According to Bolger and Parsons, maxillary sinus hypoplasia can be classified

Type I—There is mild decrease in maxillary sinus volume with normal unci-

Type II—There is mild-to-moderate reduction in volume of maxillary sinus combined with CT evidence of an absent or hypoplastic uncinate process and an absent or poorly defined ethmoid infundibulum due to uncinate process being

Type III—Maxillary sinus is primarily absent. Ethmoid infundibulum and

In our case, there was type III maxillary sinus hypoplasia (**Figures 16** and **17**).

**Figure 12.** *CT PNS showing Haller cell on left side with narrowing of infundibulum. Sinuses are still clear.*

**Figure 13.** *Coronal section of PNS showing bilateral Onodi cell.*

**Figure 14.** *CT PNS showing accessory ostia on right with clear maxillary. On the contrary, opposite sinus is hazy.*

**Figure 15.** *Endoscopy showing two accessory ostia.*

**Figure 16.** *CT showing hypoplasia of bilateral maxillary sinus.*

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**Figure 18.**

*CT showing septal pneumatisation.*

*Rhinosinusitis: How Common Are Anatomical Variations Responsible?*

surgically removes this reservoir for chronic infection [17].

KEROS type I—Depth of olfactory fossa is 1–3 mm. KEROS type II—Depth of olfactory fossa is 4–7 mm. KEROS type III—Depth of olfactory fossa is 8–14 mm.

The septum may be pneumatised as a result of extension of an aerated crista

Adenoids are present at birth and usually regress by 12–14 years of age. With advent of CT PNS, it is now clear that adenoids may persist even after adolescence. In our case, adenoids persisted till 56 years of age; this patient too had presented

There is evidence that the adenoid provides a reservoir of bacteria that may be a pathogenic factor in the development of CRS. Biofilms overlying the adenoid pad may prevent antibiotic therapy from clearing the infection. Adenoidectomy

Depending upon the depth of olfactory fossa Keros classification is as follows:

Type I is the safest while type III has high chances of skull base injury during

Asymmetry of ethmoid roof on both sides of the same patient is not uncom-

Anterior ethmoidal artery is an important landmark in sinus surgery. The anterior ethmoidal artery is seen as a classical breaking of the medial orbital wall. The artery may lie close to the skull base or may cross low within anterior ethmoid in which case the orbitocranial canal with its bony mesentery is clearly seen [4] (**Figure 25**). If the anterior ethmoidal notch is abutting the lateral lamella or the fovea ethmoidalis, the artery is considered protected during functional

mon. Hence, the surgeon should read CT thoroughly before any surgical

*DOI: http://dx.doi.org/10.5772/intechopen.83689*

• Persistent adenoids

ethmoidectomy.

intervention.

with CRS (**Figures 19** and **20**).

• Pneumatisation of septum (**Figure 18**)

• KEROS classification (**Figures 21–24**)

• Low anterior ethmoidal artery

galli or anterior extension of the sphenoid sinus.

**Figure 17.** *CT (axial section) agenesis of right maxillary sinus.*
