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Year : 2019  |  Volume : 21  |  Issue : 1  |  Page : 1-5

Anatomical variations in Computerized Tomography of paranasal sinuses in a Saudi population

Department of otolaryngology, King Abdulaziz University Hospital, King Saud University, Riyadh, Saudi Arabia

Date of Web Publication6-Feb-2020

Correspondence Address:
MBBS Yasser Albalwi
Otolaryngology, Head and Neck Surgery Department, King Abdulaziz University Hospital, King Saud University, P.O. Box 245, Riyadh 11411
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-8491.277840

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Background: The variations in structures of the nasal cavity are essential to identify while practicing endoscopic sinus surgery (ESS). Inadequate knowledge of surgeons performing ESS, regarding the commonly occurring anatomical variations can lead to a variety of complications having substantial mortality and morbidity.
Objective: This study aims to evaluate the prevalence of clinically significant anatomical variations of the paranasal sinuses in a Saudi population. Methods: A retrospective analysis of 106 computed tomography (CT) examinations of adult Saudi population were conducted to determine the prevalence of clinically significant anatomical variations of the paranasal sinuses. The study was conducted from January 2012 to October 2013 at King Abdulaziz University Hospital.
Results: The findings showed concha bullosa in 41.5% of cases, Paradoxical middle turbinate in 5.7% of cases, Haller type of cell was seen in 11.3%, Onodi type of cell in 13.2%, pneumatization of uncinate process in 3.8 % of CT scans analyzed. Internal carotid artery (ICA) bulge in the sphenoid sinus was seen in 2.8% cases, whereas no ICA dehiscence was seen in any study. Optic nerve bulge in the sphenoid sinus was observed in 9.4% of the cases.
Conclusion: Knowledge regarding the existence of anatomical variations of the sinuses has a clinical significance beyond any doubt as it minimizes the probability of surgical complications especially in ESS.

Keywords: Paranasal Sinus Diseases, Anatomic Variation, Sinusitis, functional endoscopic sinus surgery, Tomography, X-Ray Computed

How to cite this article:
Albalwi Y, Alroqi A, Alharethy S. Anatomical variations in Computerized Tomography of paranasal sinuses in a Saudi population. Saudi J Otorhinolaryngol Head Neck Surg 2019;21:1-5

How to cite this URL:
Albalwi Y, Alroqi A, Alharethy S. Anatomical variations in Computerized Tomography of paranasal sinuses in a Saudi population. Saudi J Otorhinolaryngol Head Neck Surg [serial online] 2019 [cited 2023 Jun 4];21:1-5. Available from: https://www.sjohns.org/text.asp?2019/21/1/1/277840

  Introduction Top

Chronic rhinosinusitis (CRS) is one of the most common illnesses of our time, increasing in epidemic magnitudes throughout the world[1]. It adversely impacts health- related quality of life[2],[3]. Underlying anatomical variations may be a cause of sinonasal symptoms and thus CT of paranasal sinuses is mandatory for the diagnosis and subsequent plan for management of sinusitis.

The introduction of an endoscope as a tool in sinus surgery along with the attitude of aerating and restoring mucociliary clearance has led to an enhanced interest in the anatomy of the paranasal sinuses[4]. ESS has become ofparticular importance for the otolaryngologist and is preferred for the treatment of non-neoplastic pathologies of paranasal sinuses, especially for chronic infective and polypoid sinusitis. With this technique, it is possible to open the obstructed ostia of paranasal sinuses to provide normal ventilation without damaging the adjacent structures[5]. Stammberger[6] suggested that stenosis of the ostiomeatal complex, from both the anatomical alignment and hypertrophied mucosa, can cause obstruction and stagnation of secretions that may well become infected or perpetuate infection. In any list of etiological factors associated with the development of CRS, anatomic variants are usually included. The classic list of anatomic variants includes pneumatization of the middle turbinate (concha bullosa), paradoxical twisting of the middle turbinate, bent uncinate process, pneumatization of the uncinate process, pneumatization of the aggernasi; the existence of infraorbital cells, sphenoethmoidal cells, and deviation of the nasal septum. Besides, the height of the roof, concomitant depth of the cribriform niche and septations attached to the region of the carotid artery are of surgical interest[4],[7].

A plain radiograph is of little value for ESS because\ sinus walls are obscured by overlying structures[8]. It is plausible to detect structural variations and mucosal anomalies of paranasal sinuses with CT, clearly visualizing anatomic variations of the bone which have been reported as factors contributing to recurrent and CRS[9]. The complex anatomy of the ethmoid cells does not provide an endoscopic evaluation of the ostiomeatal area, posterior ethmoid, and sphenoid sinus diseases, where coronal and axial CT offer detailed information[10]. These anatomical variations can be attributed to a repertoire of racial and genetic factors. Furthermore, there is a discrepancy of these anatomical variations among several populations and races[11].

Understanding the complex anatomy of the skull base is critical for the safe ESS; careless violation of the cribriform plate may cause cerebrospinal fluid leak, direct penetration trauma to the dura, serious intracranial and intracerebral complications[12],[13],14]. So, Preoperative CT scan assessment of patients undergoing ESS is obligatory. The radiologists usually concentrate more on pathological abnormalities than the anatomical variations and anomalies[1].

This study aims to recognize the anatomical variations of paranasal sinuses in the Saudi population; this information will be valuable for future endoscopic surgeons in understanding the pathogenesis of sinusitis and consequently avoiding iatrogenic damage due to anatomical variations. Research on these anatomical variations will provide information on the pathogenesis of sinusitis. Moreover, these facts will improve the utility of ESS in Saudi Arabia.

  Materials and Methods Top

This retrospective study comprised 106 CT scan of Saudi Arabian patients presenting to otolaryngology clinic between January 2012 and October 2013. A high resolution, 1 mm thick CT scan was taken for the study. All the patients underwent a comprehensive medical history and head and neck physical examination. We omitted patients with prior sinus surgery, sinonasal tumors, nasal polyposis, severe cervical arthropathy, or head and neck injury. Mean age when CT study was done in years was 35.38 ranging between 12.3 and 65.2.

The CT scans were interpreted in detail with particular emphasis on anatomical variations by otolaryngology surgeon in liaison with the radiologist. The various radiological features of anterior skull base structures were analyzed in detail. For all CT’s we addressed the axial and coronal views. The investigators measured the thickness of the inferior turbinate for structural and mucosal component (soft tissue). This was achieved by having a horizontal line along the thickest anterior half of the inferior turbinate and measuring that for both bony and soft tissue part of the inferior turbinate.

The septum was seen in axial and coronal views. The angle of deviation was measured in both views. In coronal view, this was achieved by measuring the worst deviation between septalattachment to skull base superiorly and hard palate inferiorly. In axial view, this was measured along the whole length of the septum, at the level which it has badly deviated. The presence of haller cells, onodi, concha bullosa, and paradoxical middle turbinate were addressed in this study. We also focused on sphenoid sinus anatomy and identified the presence of dehiscence at carotid artery area and optic nerve. The depth of lateral lamella was also measured. The frequency distributions of various findings were determined by descriptive statistics using SPSS version 21.

  Results Top

In our study out of 106 CT scan analyzed, 44.3% were male patients, and 55.7 % were females. The mean age of patients when CT was done during this study was 35.3 years. Regarding anatomical variations in our study, Deviated nasal septum was seen in 67.9 % CT’s. The mean angle of the deviated nasal septum at coronal CT was measured to be 153° [Table 1].
Table 1: Table 1: Descriptive statistics of collected data from CT

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The average depth of lateral lamella on right side in mm was measured to be 4.75 mm, whereas the depth of lateral lamella on the left side was 4.84 mm.

Anatomical variation of paradoxical middle turbinate was found in 5.7 % CT scans, out of this 3.8 % were present to the right, and 1.9 % had bilateral paradoxical middle turbinate.

Moreover, Haller type cell was seen in 11.3 % of the CT scans analyzed, of which 3.8% were bilateral, 4.7% were present to the left, and 2.8% were present to the right side. We observed Onodi type cells in 13.2% patients out of which 5.7% had bilateral Onodi type cells, 2.8% had Ondoi type cells only on the left side, and 4.7% had onodi cells on right side only. Concha Bullosa were observed in 41.5% of the CT scans, out of which 15.1% had bilateral, 9.4% and 17% were left and right-sided respectively.

We found pneumatization of the uncinate process in 3.8 % of the CT scans in this study. Pneumatization of unicate process was equal on both sides. In our study, ICA bulge in the sphenoid sinus was seen in only 2.8% of individuals. A significant finding was that we observed no ICA dehiscence in any of our patients. Regarding anatomical variations in the sphenoid sinus, optic nerve bulge was found in 9.4% of the patients. Optic nerve dehiscence was observed in 5.7% of patients. Pneumatisation in the right frontal sinus was normal in 79.2 % of individuals, however; we observed aplasia in the right frontal sinus of 6.6% patient. On the other hand pneumatization in the left frontal sinus was normal in 81.1% patients, while 4.7 % had aplasia in the left frontal sinus.

  Discussion Top

Maxillary, ethmoid, sphenoid and frontal form the four pairs of mucosa lined sinuses within the skull. CT scan of the paranasal sinuses is done in the setting of CRS as a confirmation of sinusitis on many occasions, though it is mandatory as a prerequisite for ESS[1]. CT provides surgeons with valuable information regarding disease extent, anatomic variation and anatomy of adjacent structures[6].

Haller’s cell is the pneumatization of the anterior ethmoid cells into the roof of the maxillary sinus spreading into the floor of the orbit. We found an incidence of 11.3ω/0, 3.8% were bilateral; while 4.7 % were to the left and 2.8% were present to the right side. Bolger et al. defined Haller’s cell as any cell located beneath the ethmoid bulla, lamina papyracea or orbital floor and observed Haller’s cells in 45.9% of sinus patients[15]. Kennedy and Zinreich defined Haller’s cell as ethmoid cells that project inferiorly to the ethmoidal bulla into the floor of the orbit; they observed Haller’s cells in 10% of their patients with chronic sinus complaints5. Other studies conducted to establish the anatomical variations of paranasal sinuses found similar results as compared to our present study[16],[17]. It is vital to recognize haller’s cells because they may narrow the ostium of the maxillary sinus or the ethmoid infundibulum. Stammberger and Wolf contemplate the presence of these cells a predisposing factor for recurrent maxillary sinusitis[18].

Extensive pneumatization of the middle concha is labeled as ‘concha bullosa’. This is a common variation of intranasal anatomy. It is possible to note even a very small pneumatization with the development of coronal CT. Zinreich et al. report that conchae bullosae are diagnosed best radiographically and effortlessly identified with a CT. Their look is that of airspace of the middle concha surrounded by an oval bony rim[19]. Bolger et al. reported this pneumatization in 53% of the sinus patients, as an extension of the anterior air cells (55%) or posterior (45%) ethmoidal air cells[15]. Zinreich et al. observed concha bullosa in 34% of their patients having CT for evaluation of symptomatic sinus disease, 34 of these (45%) were bilateral, and 44 (55%) were unilateral[19]. We observed concha bullosa in 41.5% of patients, 15.1 % were bilateral, 9.4 % were left sided, and 17% were right sided.

Variability in reporting different incidences is attributed to different criteria used by researchers and statistical methods. Some researchers agree to take very small and physiologically insignificant conchae as conchae bullosae. Also, the incidence depends on the patients’ group, as some studies are performed on patients with sinusitis. Tonai and Baba reported a higher of 28.1% in chronic sinus patients when compared to an incidence of 27.8% in non-sinus patients[20]. Zinreich et al. and Stammberger et al. report concha bullosa as a possible etiologic factor in recurrent sinusitis due to its negative influence on paranasal sinus ventilation and mucociliary clearance[18],[19]. Zinreich et al. reported that concha bullosa variation is linked to the nasal septal deviation, Haller’s cell, prominent ethmoid bulla and paradoxical curvature of the middle concha in 28%, 7%, 6%, and 6% respectively[19]. Similarly, in our patients, we observed paradoxical curvature of the middle turbinate in 5.7%, septum deviation in 67.9%, and Haller’s cell in 11.3 % of patients.

Pneumatisation of the uncinate process is theoretically related to ostiomeatal obstruction, tapering of the infundibulum and creating impaired sinus ventilation[10]. Bolger et al. proposed that this pneumatization is due to the growth of aggernasi cells into the uncinate process[15],[21]. We found a pneumatizeduncinate process in 3.8 % of our patients. Our findings are consistent with the findings of Bolger et al. who report its prevalence as 2.5% in sinus patients[15]. A study conducted in India, found out pneumatizeduncinate process or the uncinate bulla in 4 % cases, exclusively in males[22].

Severely deviated nasal septum compresses on the middle turbinate and contracts the middle meatus. This results in obstruction of the normal mucus movement from the sinuses and secondary inflammation and infection. We observed deviated nasal septum in 67.9% of patients. Blaugrund reports the incidence of nasal septum deviation as 20% much less in contrast to our present study[23].

Onodi cells are posterior ethmoid cells that extend posteriorly far laterally and sometimes superior to the sphenoid sinus, lying medial to the optic nerve. They are best seen on axial sections, and the surgeon should be forewarned as the optic nerve may be at risk during posterior ethmoidectomy in these cases. In our study Onodi type cell were found in 13.2% of CT scans analyzed, these results are comparable to a similar study conducted by Y. K. Maru and V. Gupta, they found onodi cells 9.8 % of CT scans analyzed[24]. We found ICA bulge in the sphenoid sinus in 2.8%. No ICA dehiscence was seen in any of our patients. Fuji et al. studied 25 cadaver sphenoid bones and found 8% of carotid arteries dehiscent of bone in the lateral sphenoid[25]. Kennedy et al. found dehiscence on the bony wall of the ICA in 25% of patients[26]. Rarely, ICA is found with mucosa covering running within the sphenoid sinus. Sareen et al. studied sagittal sections of 20 dried skulls and found dehiscence of the carotid artery in 5%[27]. Sirikci et al. reported protrusion of internal carotid artery in 26.1% of patients and dehiscence of the artery in 23%[28]. Birsen et al. come across protrusion of ICA in 30.3% and dehiscence in 5.3% of patients[29]. Sethi et al. acknowledged carotid protrusion in 93%[30], and Elwany et al. observed protrusion of carotid artery in 29% and dehiscence in 4.8% of patients[31]. This wide range of prevalence might indicate that the relationship of ICA to the sphenoid sinus may be different in the Saudi Arabian population as an ethnic group. If the surgeon is unaware of dehiscence or protrusion of the artery even disastrous hemorrhage may happen because is hardly possible to control bleeding from an injured ICA within the sphenoid sinus. Even so, neurological sequelae are unavoidable[32],[33].

In our study, we observed Optic nerve bulge in the sphenoid sinus in 9.4% of patients and optic nerve dehiscence in 5.7 % of patients. Previous studies reported a wide range of protrusion rates of 8 to 70%[34],[35]. Fuji et al. found that 4% of optic nerves were dehiscent of bone in the lateral sphenoid[25]. They also described that most optic nerves were covered by thin bone, measuring 0.5 mm or less in 78% of cases. The risk of blindness is high if the surgeon damages the nerve within the sinus[36]. Moreover, visual deficits may result from a sphenoid sinus infection or a mucocele squeezing the optic canal or nerve. Compression of the optic nerve can result in ischemia and venous blocking of the nerve. Furthermore, the optic canal is the place where the optic nerve is least nourished, which makes it very prone to injury[11],[37].

We perceived a wide range in the literature for the incidence of variations. This sometimes depends on the depiction of the variation as in haller’s cell and concha bullosa, or on the group of patients studied. The incidence of variations in the literature was higher in sinus patients when compared to that in non-sinus patients because these variations usually predispose to sinus diseases. It is also likely that the incidences may vary due to the ethnic differences of the populations studied.

  Conclusions Top

This study provides numerous variations of the nasal cavity for the otolaryngologist to be a guide for the most accurate information in therapeutic decisions and also to be a guide for the otolaryngologist and radiologist in the evaluation with coronal CT, which provides easy identification of the intricate anatomy, complements endoscopic examination and guides ESS.

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