Nasal anatomical and pathological variants in patients with antrochoanal polyps

Introduction

Antrochoanal polyps (ACP) are from the most common unilateral sinonasal benign lesions. They are edematous mucosa that start from the maxillary antrum. They pass from the ostium of the maxillary antrum and extend to the posterior nasal opening (choana)^[1]. The pathogenesis of ACP is still unknown. There are many theories explaining its pathogenesis. Some authors believe that maxillary sinus retention cysts are the origin of ACP^[2]. Others suggest that nasal allergies and inflammatory processes play an important role in formation of edematous mucosa that progress to form ACP^{[3, 4]}. Nasal anatomical and pathological variants have been suggested to be from the predisposing factors to ACPs. These anatomical variations may be the cause of physical factors that lead to ACPs formation.

Materials and methods

This prospective study was conducted at our Otolaryngology department. The study was approved by the Institutional Review Board at our University. The study was registered in ClinicalTrials.gov ID: NCT05989919. In this study, all participants were informed about the research and signed informed consent before data collection.

The study participants were recruited from patients attending outpatient clinic.

During the period from December 2022 to August 2023, we selected 40 patients with ACPs who had the following inclusion criteria: 1-radiologically diagnosed based on CT nose and PNS. 2-histopathologically diagnosed as ACP. The radiological diagnosis is based on seeing low attenuated soft tissue mass filling the maxillary antrum and extending through the middle meatus into the nasal cavity and directs towards the post nasal opening.

We excluded:

• patients with history of maxillofacial trauma.
• 2- patients who had previous nasal surgery.

To be more objective, a control group of 40 patients who had unilateral maxillary sinusitis.

We assessed multislice computed tomography (CT) nose and paranasal sinus images by Toshiba aquilion CT scanner. Axial and coronal 2.5mm cuts were obtained.

Both study and control groups were compared regarding anatomical and pathological variations in the nose. These variants include: deviated nasal septum, concha bullosa, paradoxical middle turbinate and uncinate process insertion (to lamina papyrecea or roof of ethmoid or middle turbinate). We also compare between them according to presence of retention cyst in CT in contralateral side

We also evaluate the sclerosis on thickening of the bony wall of the paranasal sinus as an indication of chronic inflammation.

Statistical analysis

SPSS 24.0 program was used for statistical analysis. Averages and standard deviations were calculated. The Mann–Whitney and Chi‑square tests were used for comparisons between the groups. The Pearson correlation tests was used to evaluate correlations. Statistical significance was set at ≤ 0.05.

Results

The research included 80 cases divided into 2 groups: ACP group (40 cases) and control group (40 cases).

Table (1) shows the demographic data of the cases in each group. In ACP group, the mean age of subjects is 26.93±11.92 years. There are 25 males and 15 females. While in control group, the mean is 27.78±12.46 years. There are 24 males and 16 females. There is no significant difference in age or gender between both groups (P=0.756, 0.818 respectively).

The presence of retention cyst in the contralateral maxillary antrum was significantly higher in ACP group [15 cases (37.5%)] than in control group [3 cases (7.5%)] (P=0.001). Figure (1,2).

The presence of sinus wall thickening and sclerosis wasn’t significantly different between ACP group and control group (P=0.396).

The difference between ACP group and control group regarding the presence of concha bullosa and paradoxical middle turbinate was found to be statistically insignificant (P=0.456, P=0.629 respectively).

There was no significant difference in the variation of superior uncinate insertion between the ACP group and control group either to lamina papyrecea, or ethmoid roof or middle turbinate (P=0.501, 0.633, 0.105 respectively). All of the previous results are shown in table(2).

When we compared both ACP group and control group in the presence of deviated septum as shown in table(3), we found 22 (55%) cases with deviated nasal septum to opposite side of pathology in ACP group [figure(3)] and 8 (20%) cases in the control group and that was statistically significant (P=0.001). On the other hand, we found 8 (20%)cases with deviated nasal septum to same side of pathology in ACP group and 12 (30%) cases in the control group and that was statistically insignificant (P=0.302).

Discussion

ACP has been known for a long period of time however, the pathophysiology of its formation and predisposing factors are still questionable. Many researches have been done to relate different factors to the formation of ACP.

In a research done by Berg et al., it was mentioned that retention cyst is the precursor of ACP. This theory was based on the histological similarity between ACP and the retention cyst^[2].  In our study, the presence of retention cyst in the contralateral maxillary antrum was signifi-cantly higher in ACP group than in control group (P=0.001). This supports that ACP may have been a retention cyst originally.

Frosini et al., clarified this conversion according to Bernoulli theorem^[5]. It stated that the air flow passing within a narrow area increases in velocity and decreases in pressure. The flow of air during inspiration increases, and according to this theory the pressure decreases so the nasal walls collapse. During expiration, the air outlet from the maxillary ostium decreases, so the pressure in the maxillary antrum increases causing herniation of the polyp.

Presence of inflammation leads to narrowing of the maxillary ostium, thus aggravates the condition. Gursoy et al., suggested that chronic inflammation is an important factor that predisposes to ACP formation^[6]. He used the presence of sclerosis in the maxillary sinus as an indicator of chronic inflammation. In their study, there was a significant difference between ACP group and control group in the presence of sclerosis (P=0.001). However, in our study, the presence of sinus wall thickening and sclerosis wasn’t significantly different between ACP group and control group.

When we compared the presence of nasal septal deviation between both groups in our research, we found 22 (55%) cases with deviated nasal septum to opposite side of pathology in ACP group [figure(2)] and 8 (20%) cases in the control group and that was statistically significant (P=0.001). In a study by Hekmatnia et al, the cases of ACP has a higher frequency of deviated nasal septum^[7]. Aydin et al. found that the nasal septum is deviated to the opposite side of ACP They suggested that this occurs with the same way as the compensatory hypertrophy of inferior turbinate in the side opposite to septal deviation^[8]. Elahi et al., said that ACP developed in the concave side of deviated nasal septum due to associated middle turbinate abnormalities on the side opposite to deviated septum^[9].

Unfortunately, we couldn’t assess whether the formation of ACP lead to deviation of nasal septum to other side or the septum was deviated before the formation of ACP and affected air flow in the nasal cavity leading to ACP formation. This is due to the difficulties in monitoring the process of ACP formation from the start of the pathology.

Other anatomic variants including: paradoxical middle turbinate, concha bullosa and variation in superior insertion of uncinate was statistically insignificant when we compared ACP group and control group. This agrees with the study done by Gursoy et al.,^[6].

In this research, male : female ratio is 1.6: 1, other studies done by Aktaş et al., & Bozzo et al.,  showed higher incidence in males^{[10, 11]}.

We need to make more studies about resistance of air flow in the nasal cavity and pressure changes by objective methods to support the results of our research.