|Year : 2019 | Volume
| Issue : 5 | Page : 603-608
Anatomic variations associated with antrochoanal polyps
M Gursoy1, N Erdogan2, YK Cetinoglu2, F Dag2, E Eren3, ME Uluc2
1 Department of Radiology, Faculty of Medicine, Izmir Democracy University, Izmir, Turkey
2 Department of Radiology, Izmir Katip Celebi University Ataturk Training and Research Hospital, Izmir, Turkey
3 Department of Otorhinolaryngology, Izmir Katip Celebi University Ataturk Training and Research Hospital, Izmir, Turkey
|Date of Acceptance||17-Jan-2019|
|Date of Web Publication||15-May-2019|
Dr. M Gursoy
Izmir Democracy University, Faculty of Medicine, Gursel Aksel Bulv. No: 14, Karabaglar, Izmir
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: Although more than a century has passed since antrochoanal polyps (ACPs) were first defined, etiopathogenesis still remains unclear. The aim of this study was to investigate the relationship between ACPs and sinonasal cavity variations. Subjects and Methods: One hundred and forty-four patients with ACP on paranasal sinus computed tomography scans (ACP group) and 160 paranasal sinuses without ACP (control group) were included into the study. The study group was evaluated in respect of the presence of retention cyst in the contralateral maxillary sinus and sinus bone wall sclerosis thickening. Both groups were also compared with respect to the frequency of sinonasal anatomic variations, nasal septal deviation, variations of the uncinate process insertion, concha bullosa, paradoxical middle turbinate, and accessory maxillary sinus ostium. In the ACP group, the cases with septal deviation (SD) were also evaluated whether the deviation convexity was towards the polyp side or the opposite side. In addition, the posterior extension of ACPs were evaluated in three groups as middle meatus, nasopharynx, and oropharynx extension. Results: The prevalence of retention cyst, sinus wall sclerosis thickening, SD, and accessory maxillary ostium was significantly higher in the ACP group. A negative directional correlation was determined between the SD side and ACP side. When the ACP extensions were examined, middle meatus extension was seen in 32.6%, nasopharynx in 56.3%, and oropharynx in 11.1%. Conclusion: Accessory ostium may be an accelerating factor in the transformation of retention cyst to ACP. Furthermore, the changes in the nasal passage airflow on the opposite side suggest that SD contributes to this process.
Keywords: Antrochoanal polyp, computed tomography, paranasal sinus, sinonasal variation
|How to cite this article:|
Gursoy M, Erdogan N, Cetinoglu Y K, Dag F, Eren E, Uluc M E. Anatomic variations associated with antrochoanal polyps. Niger J Clin Pract 2019;22:603-8
|How to cite this URL:|
Gursoy M, Erdogan N, Cetinoglu Y K, Dag F, Eren E, Uluc M E. Anatomic variations associated with antrochoanal polyps. Niger J Clin Pract [serial online] 2019 [cited 2019 Jul 22];22:603-8. Available from: http://www.njcponline.com/text.asp?2019/22/5/603/258274
| Introduction|| |
Antrochoanal polyps (ACPs) are lesions with benign solitary characteristics, which originate from the maxillary sinus edematous mucosa and show extension towards the choana by passing the natural or accessory maxillary sinus ostium. Histologically, ACPs are formed of a cystic component located within the maxillary sinus and a solid component emerging mostly from the accessory maxillary sinus ostium and at a lower rate from the natural maxillary ostium. The etiology of ACPs is still a matter of debate. That there is no histological difference between maxillary sinus retention cysts and the cystic part of ACP within the maxillary sinus supports the hypothesis that retention cysts could be the precursor lesions of ACPs. It has also been reported that inflammatory processes such as chronic sinusitis and allergies could be responsible in the etiology., These inflammatory processes could first cause edema in the maxillary sinus mucosa, followed by the formation of retention cysts in the maxillary sinus.
Therefore, the question arises regarding what are the physical factors causing a silent antral cyst to push from the natural or accessory maxillary sinus ostium to nasal cavity and start ACP formation. It has been suggested that anatomic variations of the sinonasal cavity could be one of the preparatory factors. Although more than a century has passed because ACPs were first defined by Killian, there are still unanswered questions and knowledge is still limited about the role of physiopathologic situations played in the development of ACPs.
The aim of this study was to investigate whether or not there is a relationship between ACPs and sinonasal cavity variations.
| Subjects and Methods|| |
This retrospective study was approved by the Institutional Review Board of our hospital. Due to the retrospective nature of the study, informed consent was not required from patients.
Patient inclusion and CT review
A retrospective evaluation was made of 144 patients (50 female, 94 male, mean age: 36.0 ± 16.15 years) who presented at our clinic between January 2008 and August 2017 for paranasal sinus computed tomography scan (PNS CT) and were operated on with an initial diagnosis of ACP on PNS CT, and had the diagnosis histopathologically confirmed (ACP group). The diagnosis of ACP was made when a low-attenuating soft tissue mass fills the maxillary sinus growing through the accessory or natural ostium into the middle meatus and choana on CT scan. Patients were excluded if they were diagnosed with ACP but had previous maxillofacial trauma, a history of paranasal sinus or nasal surgical intervention, or findings of severe chronic sinusitis. In addition, for more objective investigation of whether or not sinonasal cavity variations have a role in the etiopathogenesis of ACP, a control group formed of160 paranasal sinuses of 80 patients without ACP on PNS CT scans was included into the study. The same exclusion criteria were used for the control group.
In all of the cases, multislice CT (Somatom Definition, Siemens Healthcare, Forchheim, Germany, ICT 64; scan setting, 120 kV, 60 mAs) was used with scan field of view (FOV) of 250 mm and an image matrix of 512 × 512. Coronal and sagittal MPR images were obtained on axial plane images taken parallel to the hard palate.
In the PNS CT evaluation, the study group was evaluated with respect to the presence of retention cyst in the contralateral maxillary sinus, the presence of sclerosis and thickening of the sinus bone wall, which is a sign of accompanying chronic inflammation. Control group was also evaluated in respect of the presence of retention cyst in bilateral maxillary sinuses. Both groups were also compared in respect of the frequency of sinonasal anatomic variations, nasal septal deviation, variations in the superior insertion of the uncinate process, concha bullosa, paradoxical middle turbinate, and accessory maxillary sinus ostium. In the ACP group, the cases with septal deviation were also evaluated whether the deviation was towards the polyp side or the opposite side. The direction of deviation was described by the convexity of the septal curvature.
Uncinate process insertion variations were evaluated in three groups. Insertion to the lamina papyracea laterally was categorized as type 1, insertion to the roof of the ethmoid was type 2, and insertion to the middle turbinate medially was type 3. The relationship between uncinate process insertion variations and ACP was investigated. In addition, on the basis of its posterior extension, the ACP cases were classified into three groups namely middle meatus, nasopharynx, and oropharynx extension.
Data analyses were performed using SPSS, version 24.0. Mann–Whitney U-test analysiswas used to compare the age distribution, and Chi-square analysis was used to compare gender distribution between the groups. The presence of anatomic variations in the ACP group and the control group was examined using Chi-square analysis. The correlations were evaluated with Pearson correlation analysis, and the Kappa test was also applied for the adjustment. The alpha level of statistical significance was set at 0.05.
| Results|| |
There was no significant difference in the age distribution of the two groups (P = 0.694). In the study group, a significant difference was found in the distribution of ACP between male and female patients, with a significantly higher prevalence in males (P = 0.002) [Table 1].
The prevalence of retention cyst on the contralateral site of the ACP, sinus wall thickening and sclerosis, septal deviation, and accessory maxillary sinus ostium was significantly higher in the ACP group (P = 0.001) [Table 2].
|Table 2: Comparison of retention cyst, sinus wall sclerosis-thickening and sinonasal anatomic variations between the control group and ACP group|
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The most common anatomic variation observed on CT scans was nasal septal deviation, which was seen in 47 patients in the control group (58.8%) and 119 patients in ACP group (82.6%) (P = 0.001). In 41 patients (34.5%), septal deviation convexity was determined on the same side with ACP, and in 78 (65.5%) patients, it was towards the opposite side. A negative directional correlation was determined between the septal deviation side and ACP side (P = 0.002, Kappa = −0.270) [Figure 1] and [Table 3].
|Figure 1: Coronal CT image shows low-attenuation soft tissue mass (asterisk) protruding from the accessory maxillary sinus ostium. Nasal septal deviation was determined on the opposite side of ACP. Accessory maxillary sinus ostium was present bilaterally (arrow)|
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|Table 3: Comparison of nasal septal deviation between the control group and ACP group|
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Accessory maxillary sinus ostium was statistically significantly higher in the ACP group (P = 0.001). Accessory ostium was determined in 105 (72.9%) of 144 patients in the ACP group, and in all these cases, the ACP was herniated to the middle meatus via the accessory ostium. In 39 (27.1%) patients, the herniation was via the natural ostium. Cases where the ACP herniated through the accessory ostium were evaluated regarding whether the maxillary natural ostium and ethmoidal infundibulum was obstructed or not. The ipsilateral maxillary natural ostium and ethmoidal infundibulum were found to be obstructed in 74 of 105 patients (70.5%) and not obstructed in 31 (29.5%) patients.
The accessory maxillary sinus ostium was bilateral in 61.9% (65/105 patients) of the ACP group and in 72.7% (24/33 patients) of the control group. No statistically significant difference was determined between the two groups in respect of the frequency of bilateral accessory maxillary sinus ostium (P = 0.283).
There was no statistically significant difference between the groups in respect of the variations in the superior insertion of the uncinate process, concha bullosa and paradoxical middle turbinate (P > 0.05) [Table 2].
When the ACP extensions were examined, type 1 (middle meatus) was seen in 47 patients (32.6%), type 2 (nasopharynx) in 81 patients (56.3%), and type 3 (oropharynx) in 16 patients (11.1%) [Figure 2]a and [Figure 2]b.
|Figure 2: (a and b) Coronal CT image shows the antrochoanal polyp (asterisk) filling the whole left maxillary sinus, protruding from the accessory maxillary sinus ostium. There is a retention cyst in the contralateral maxillary sinus (a). Axial CT image shows the same mass growing posteriorly to reach the nasopharynx (arrow) (b)|
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| Discussion|| |
Despite the length of time that has passed since the first definition of ACP, its etiology is still a matter of debate. There are many studies in literature on this subject related to the role of various factors. In a study by Berg et al., it was stated that chronic inflammation may cause obstruction of small seromucinous glands on the mucosal surface, and then retention cysts formed as a result of this obstruction could be responsible for the formation of ACP. This hypothesis is based on the cystic component of the ACP and retention cysts having the same histology. So, how does a retention cyst become an ACP? Frosini et al. explained the transformation of a retention cyst to an ACP using the Bernoulli theorem. According to this, the flow of air passing through a narrow area accelerates in speed and reduces in pressure. The rate of airflow in inspiration increases, and because of this phenomenon the nasal walls collapse. During expiration, there is reduced outlet of air from the maxillary natural ostium, which is narrowed due to chronic inflammation. Increasing the pressure within the antrum causes herniation of the polyp from the accessory maxillary sinus ostium. To show the presence of chronic inflammation in the current study, the frequency of concomitant ipsilateral sinus bone sclerosis was compared in the two groups and the rate in the ACP group was determined to be statistically significantly higher than that of the control group (P = 0.001). The frequency of retention cysts, which could be precursor lesions of ACP, was also compared in both groups. The retention cyst frequency in the contralateral maxillary sinus was found to be higher in the ACP group than that in the control group (P = 0.001). In addition, the natural ostium and ethmoidal infundibulum were obstructed because of mucoperiostal thickening in 70.5% of the cases (74/105), which leaves the maxillary sinus via accessory ostium in ACP group. When all the findings were combined, it was concluded that the process starts with the formation of a retention cyst as a result of chronic inflammation (infectious, allergic etc.), and the same inflammation causes a narrowing in the natural maxillary ostium. The pressure differences formed in the maxillary sinus force the retention cyst to herniate through the accessory ostium, thus giving rise to ACP formation.
With this theorem, Frosini et al. assumed that all ACP cases had maxillary accessory ostium. In the current study, herniation in all the cases with accessory maxillary sinus ostium was determined to be via the accessory ostium (105/144, 72.9%). However, 39 (27%) patients in the ACP group did not have accessory maxillary sinus ostium, and the herniation had occurred through the natural maxillary ostium. In a study by Balikci et al., it was reported that 97.5% of ACPs left the maxillary sinus via the accessory ostium, whereas Stammberger and Hawke reported this rate to be 70%., Therefore, this theory is insufficient to explain the pathogenesis of ACPs, which herniate from the maxillary sinus through the natural ostium. There is a need for new hypotheses to clarify the pathogenesis of ACPs, which protrude through the natural maxillary ostium. In the current study, accessory maxillary sinus ostium was frequently seen bilaterally in both the ACP and control group. In 65 (61.9%) ACP group patients, accessory ostium was determined in the contralateral maxillary sinus. So, what are the factors determining on which side an ACP will develop? Could sinonasal anatomic variations be a factor or could negative intranasal pressure contribute to this? To answer this question, the ACP and control groups of this study were compared in respect of the frequency of various sinonasal anatomic variations. The most commonly seen anatomic variation was nasal septal deviation, and it was seen at a statistically significantly higher rate in the ACP group. Similarly, in a study by Hekmatnia et al., the single variation seen at a statistically significantly high rate was septal deviation. In addition, in our study, nasal septal deviation convexity was on the same side with the ACP in 41 patients (34.5%) and toward the opposite side in 78 (65.5%) patients. There was a negative agreement regarding ACP and the septal deviation sides. Aydin et al. also found negative agreement between septal deviation sides and ACP. They thought that there was a similarity to compensatory inferior concha hypertrophy, which developed on the opposite side to the septal deviation, and ACPs could develop with the same mechanism. Elahi et al. found that the osteomeatal complex obstruction was higher on the opposite side to the septal deviation. This obstruction was related to contralateral middle concha abnormalities, which developed secondary to nasal septal deviation. In the current study, the natural maxillary ostium was obstructed due to mucoperiostal thickening in 70.5% of the ACP group. It seems as if both negative pressure within the maxillary sinus and septum deviation contribute to natural maxillary ostium obstruction. That a high rate of ACPs was seen on the opposite side to the septum deviation suggests that it could be related to the functional air passage and high aerodynamics of the airflow associated with the deviation. However, as it was not possible to monitor the development process of ACPs from the beginning to end, it is a limitation of the study that it could not be proven whether or not polyp's mass effect or accelerated air flow associated with the narrowing of the nasal passage constitute nasal septal deviation.
Although other sinonasal anatomic variations (superior insertion of the uncinate process, concha bullosa and paradoxical middle turbinate) were seen higher in the ACP group, no statistically significant difference was determined.
When the ACP extensions were examined, type 1 (middle meatus) was seen in 47 patients (32.6%), type 2 (nasopharynx) in 81 patients (56.3%), and type 3 (oropharynx) in 16 patients (11.1%). To our knowledge, there is no extensive series study in literature related to ACP extensions. Thus, the current study is the first on this subject with an extensive patient group to report the rates. ACPs extend to the nasopharynx most often. The number of cases with ACP showing extension to the oropharynx is limited, which is rarely seen.,,, In the light of these data, that 67.4% of the ACPs in the current study were determined as extended to the nasopharynx and oropharynx is proof that diagnosis was made in the late stage.
When the ACPs were examined according to gender, the male/female ratio of the current study was 1.8:1. Previous studies in literature have similarly reported a higher frequency of ACPs in males.,,
After the study by Frosini et al. involving 200 cases, the current study is the next largest patient series on this subject and the largest one with a control group in literature. Having a control group is one of the superiorities of this study. A limitation of the study is that it was retrospective. There is a need for further studies to be conducted with objective measurement methods of the airflow resistance and pressure in the nasal cavity for ACP etiopathogenesis to be more clearly explained.
| Conclusion|| |
Although a long time has passed since ACPs were first defined, its etiopathogenesis has still not been fully clarified. However, the statistical data of this study support that retention cysts, which form as a result of chronic inflammation, herniate to the nasal cavity with the negative pressure effect created within the maxillary sinus. The higher incidence of accessory ostium in ACP cases and that herniation of the polyps was seen through the accessory maxillary sinus ostium strengthen the view that accessory ostium may be an accelerating factor in the transformation of retention cyst to ACP. Furthermore, the changes in the nasal passage airflow on the opposite side suggest that nasal septal deviation contributes to this process.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]