The anatomic abnormalities and pathological conditions of the sino-nasal complex can be easily identified using computed tomography (CT).12 As cone-beam CT (CBCT) has become more widespread, features of the nose and paranasal sinuses have become more easily identified by oral radiologists, with higher accuracy.3 In the osteo-meatal complex region, concha bullosa (CB) is considered the most common anatomic variation.4 It can be simply described as a pneumatized middle turbinate. The causes of pneumatization are unclear, although trauma, nasal septal deviation (NSD), and mouth breathing have been established as predisposing factors of CB.5 Earwaker reported a prevalence of CB of 55% of his sample,6 whereas Zinreich et al.7 reported that CB was present in 34% of their sample. CB can compromise the middle meatus, particularly the osteo-meatal complex, which in turn may make maxillary sinus disease more likely due to the compromised mucociliary drainage.37 Although the majority of cases of CB are asymptomatic, ongoing research is being conducted into its association with sinus disease, when the osteo-meatal complex is blocked.89

NSD is a very common problem among individuals from the Middle East.10 The most common reported cause of septal deformity is trauma during infancy and childhood.5 However, there is little evidence regarding the possibility that NSD or pneumatization of the middle turbinate may act as a potential contributor to MSV changes and subsequent sinus pathology. In the literature, NSD and CB have been found to interfere with proper air flow, which in turn may increase an individual's predisposition to sinus disease, but the relationship of this phenomenon with volumetric changes of the maxillary sinuses remains to be clarified.11 The objective of this study was to determine the prevalence of CB, NSD, and sinus pathology in a selected sample of Emirati individuals and to explore the possible association of these findings with MSV changes.

The data collection for this retrospective study was approved by the Medical Ethics Committee of the University of Sharjah, United Arab Emirates (UAE). A total of 106 maxillofacial CBCT scans were taken over the course of 2 years (from October 2015 to October 2017) at the College of Dental Medicine, University of Sharjah (Sharjah, UAE). The study sample was limited to Emirati adults over the age of 18 years. Patients' medical records were reviewed to exclude individuals with a positive history of any prior sino-nasal surgery and/or craniofacial trauma.

All scans were taken using the Galileo 3D X-Ray system (Sirona Dental Systems, Long Island City, NY, USA) with a voxel size of 150 µm. The images were reproduced and observed on the axial, coronal, and sagittal planes, and all scans were reviewed for any abnormalities in the sino-nasal complex, especially CB, NSD, and maxillary sinusitis. The direction of NSD and the angle of deviation were measured on coronal CBCT images. The angle of deviation was defined as “the angle between the crista galli and the most prominent point of deviation”.12 The convex part of the nasal septum was identified as the direction of deviation. Patients were subsequently split into 3 groups according to the severity of NSD, defined by the angle of deviation: mild (less than 9°), moderate (9°–15°), and severe (greater than 15°)12 (Fig. 1). CB were classified according to the direction of NSD as unilateral, contralateral, or bilateral.

In accordance with Rak et al.,13 maxillary sinusitis was defined as a radiographic mucosal thickening greater than 3 mm. The likelihood of asymmetries arising as a result of incorrect patient positioning and lack of position standardization was considered, and reference lines were used to correct the measurement plane in all patients. Multiplanar reconstructed coronal and sagittal images were generated and reviewed, and the greatest dimensions of the maxillary sinus were recorded. Sinus height was measured on coronal reconstructed images, from the lowest point of the sinus floor to the highest point of the sinus roof. Maxillary sinus width was measured on coronal reconstructed images as the longest perpendicular distance from the medial wall of the sinus to the outermost point of the lateral wall of the maxillary sinus (Fig. 2). The anteroposterior dimension of the sinus was measured as the longest distance antero-posteriorly from the most anterior point to the most posterior point on sagittal reconstructed images (Fig. 3). MSV was measured using the airway tool of Dolphin 3D imaging software version 11.8 premium (Dolphin Imaging, Chatsworth, CA, USA) from reconstructed Digital Imaging and Communication in Medicine images (Fig. 4). To determine the reproducibility and reliability of the measured variables, intra-examiner calibration was performed by comparing 20 randomly selected CBCT measurements made by the same radiologist (AU) at a 2-week interval using the paired-sample t-test. No statistically significant difference was noted between the first and second measurements (P>0.05).

SPSS for Windows (version 23.0; IBM Corp., Armonk, NY, USA) was used to perform the statistical analysis. Categorical variables were presented as percentage and frequency, and continuous variables were indicated by mean, standard deviation, range, and their minimum/maximum values. The independent and paired t-tests were also used to compare mean values. A multiple linear regression model was constructed using a backward selection logarithm. For the statistical comparisons that were made, statistical significance was considered to be present at P<0.05.

The average age of the patient population examined was 39.25±15.61 years, and the age range was 18–71 years. The mean right and left MSV was 16.30±12.79 cm³ and 15.05±7.57 cm³, respectively. The difference between sides was not statistically significant (P>0.05) (Table 1), although males tended to have significantly greater sinus dimensions than females. Nonetheless, the MSV did not show a significant difference according to sex (Table 1). CB was found in 37% of females and in 38.8% of males, with no statistically significant sex difference (Fig. 5).

NSD was found in 68.5% (n=77) of females and 80.8% of males, with no statistically significant difference by sex. The prevalence of sinus pathology was significantly higher in females (64.8%) than in males (88.5%) (Table 2). Overall, the prevalence of bilateral CB was higher in males than in females (23.1% and 11.1%, respectively), while a higher frequency of unilateral CB was detected in females than in males (25.9% and 15.4%, respectively); however, this difference was not significant. Bilateral sinus pathology was more common in males (65.4%) than in females (37%), while an almost equal proportion (~25%) of unilateral sinus pathology was observed in both sexes.

Although the relative frequency of CB was clearly higher among individuals with NSD (40.5%) than among those without NSD (29.6%), the association between CB and NSD was not statistically significant (P>0.05) (Table 3). Similarly, there was no significant relationship between NSD severity and the prevalence of CB, although it was noted that individuals with mild NSD had a higher rate of CB (45.5%) than those with severe NSD (12.5%).

The relative frequency of detected sinus pathology was higher among individuals with NSD (79.7%) than among those without NSD (66.7%), but the association was not statistically significant. Likewise, although this tendency was not significant, those with mild NSD had a higher frequency of sinus pathology (84.8%) than those with severe NSD (62.5%) (Table 3). The presence of middle CB had no statistically significant association with the presence of sinus pathology.

Table 4 shows the impact of several studied parameters on MSV. Only the presence of middle CB was associated with a significantly higher MSV.

The presence or absence of NSD did not affect MSV, although the sinus size appeared smaller on the deviated side than on the non-deviated side. Bilateral CB was linked to a larger MSV in comparison to cases without CB or with only unilateral CB, and the MSV was significantly higher in the presence of CB (Table 5).

CBCT is a cost-effective method that is being used with increasing frequency for the diagnosis of maxillofacial structures.14 Maxillofacial and oral radiologists should be familiar with the sino-nasal complex region. The sino-nasal cavity is conventionally imaged using CBCT exams of the jaws. However, some anatomic variations may lead to chronic sinusitis or complications during sinus surgery, including procedures such as sinus lift surgery, which is performed prior to dental implant placement. Thus, a meticulous understanding of the anatomy of the sino-nasal complex is of great importance for minimizing and/or eliminating surgical complications.15 NSD is the most common anatomical variation of the nasal cavity, and it was reported by Earwaker that “NSD occurs in 44% of individuals with a slight right-side predominance and equal gender distribution.”6 In the present study, more than two-thirds (79.9%) of the studied sample had NSD, primarily mild or moderate NSD (45.5% and 34.4%, respectively). Deviation of the septum may exacerbate snoring or obstruct breathing if it is severe enough that the septum contacts the lateral nasal wall. In the present investigation, severe NSD was only seen in 7.5% of the studied sample. Shin suggested that the development of unilateral sinusitis might be influenced by NSD.16 According to a meta-analysis conducted by Collet et al., there was “no relationship between the degree of deviation and the presence of sinusitis.”17 Kapusuz et al. reported that the MSV was influenced by severe septum deviation and suggested that the MSV was usually smaller on the deviated side than on the opposing side.18 This tendency was also suggested by Lee et al., and is in agreement with the present findings of this study.19 Moorthy et al. demonstrated that an S-shaped NSD was significantly correlated with sinus diseases, including cases where nasal symptoms were absent.20 Erkan et al.21 suggested that both NSD and CB might affect each other physically. In the literature, few studies were found that sought to assess the correlation between NSD and the presence of middle turbinate pneumatization; however, a study demonstrated a highly significant correlation between the presence of middle CB and a deviated septum on the contralateral side.18 It has been suggested that the abnormal space created in the nasal septum by the concave part may provide conditions suitable for pneumatization of the middle turbinate.22 NSD was usually accompanied with a dominant large CB.2223 In contrast, in this study, only 40.5% of the individuals with NSD had CB, suggesting there may not be an association. Some investigators have suggested that there may be a relationship between having CB and sinusitis, but other reports found no such relationship.162425 In this study, positivity for both NSD and CB had no significant impact on the presence or absence of sinus pathology (P>0.05). The exact mechanism of CB formation is not yet clear, but the prevalence of middle CB has been reported to range from 13% to 72.2%.3526 CB may originate from unilateral or bilateral “variation in the pneumatization of the bone plate caused by an extension of ethmoid cells.”27 Miranda et al.27 suggested that “the degree of pneumatization varies and may cause obstruction of the middle meatus or infundibulum.” In the present study, middle CB was observed in 37.7% of the sample; 20.7% of the sample had single unilateral CB, and 16.6% had single bilateral CB. This differs from the findings described in previous studies,2428 and according to the study conducted by Subramanian et al.,29 the prevalence of CB among females was higher than among males. However, in the present study, CB was detected in both sexes equally, with single unilateral CB being the most common variant among females. Abnormalities of the concha may predispose individuals to osteo-meatal obstruction, which may lead to chronic sinusitis.2930 There also seems to be a connection between increased MSV and CB. Additionally, the sinus volume in the presence of bilateral and/or dominant CB was slightly larger than when CB was not present. This could be attributed to the intensified growth of the maxillary sinus as a result of inadequate ventilation secondary to the presence of CB. Smith et al. reviewed 883 CT scans, in order to determine the prevalence of CB and NSD and their possible association with maxillary sinus morphology, and failed to find a significant relationship between them.31 Similarly, Göçmen et al.32 reviewed 300 CBCT scans, were not able to demonstrate “a definite role for NSD, CB and Haller's cells on sinus pneumatization,” and suggested the need for further studies in order to clarify the relationship among these phenomena. In the present study, maxillary sinus asymmetry was not affected by the presence of CB and/or NSD, which is in agreement with the study conducted by Demir et al.33 Uygur et al.28 suggested that “the NSD angle plays an important role on the pneumatization of the concha on the opposite side.” In the present study, a non-statistically significant difference was observed between the angle of deviation and the direction of CB (P<0.05). Kucybata et al.34 retrospectively analyzed 214 paranasal sinus CT scans in order to investigate whether positivity for NSD and CB was associated with the occurrence of maxillary sinusitis, and concluded that only NSD was related to maxillary sinusitis. Additionally, they demonstrated that bilateral CB had an effect on MSV, which agrees with the present study.

The prevalence and distribution of CB in this study are similar to the findings of studies conducted in Poland and Iran,3435 whereas the prevalence of NSD in this study is similar to the findings of studies conducted in Poland and Portugal.2334

In conclusion, NSD and CB were found to be common radiographic findings in asymptomatic Emirati patients. Although NSD was observed in more than two-thirds of the sample and CB was observed in more than one-third of the sample, only CB had a significant impact on MSV.