Introduction: Rhinosinusitis is the inflammation of the nasal mucosa of one or several paranasal sinuses. In a radiological practice, anatomical variations are common in tomographic studies. The importance of these variants resides in their predisposition to mechanical obstruction, which can cause sinus disease. Few studies have quantitatively defined the influence of each variable and its relation to rhinosinusal disease.

Objective: Determine the frequency of the anatomical variations of the paranasal sinuses in patients diagnosed with chronic rhinosinusitis, in RGH No.1 of Tijuana, Baja California.

Methods: A descriptive, analytical and retrospective study was carried out in patients with chronic rhinosinusitis in the RGH No. 1 of IMSS, in Tijuana during July to September 2018. It received prior authorization by the local research committee. The studied variables were: age, gender, presence of septum deviation, sinus involved and anatomical variation. A descriptive statistics analysis was carried out, with measures of central tendency and dispersion for quantitative variables, and frequencies for qualitative ones. Pearson's Chi-Squared test and Cohen's Kappa Index were also used with the SPSS statistical program.

Results: The most frequent anatomical variants in the paranasal sinuses of patients diagnosed with chronic rhinosinusitis were the deviation of the nasal septum, presence of bullous shells and pneumatization of the sphenoid sinus. After applying Cohen's Kappa, these results were found to be consistent with the results of two independent observers. Meanwhile, the Chi-Square test identified that anatomical variants are not related to age and sex.

Conclusion: The majority of patients presented only one anatomical variation. Patients aged 18 to 24 years old were the most affected and deviation of the nasal septum was the most frequent variation. Suggestions for future studies include researching the relationship between age or degree of clinical involvement and the anatomical variations.

Keywords: anatomical variations, paranasal sinuses, sinusitis, tomography, multislice computed tomography

Rhinosinusitis is the inflammation of the nasal mucosa of one or more paranasal sinuses (PNS).¹ The nasal anatomy varies from one person to another, so it is common to identify various anatomical variants in the general population. Some of them are considered to be predisposing factors for mechanical obstruction, which can lead to sinus disease.^2,3 Some of the most common variants are: bullous shells, prominent agger nasi cells, Haller or Onodi cells, paradoxical middle turbinate, prominent ethmoid bulla, pneumatization of the sphenoid sinus or crista galli, and deviation of the lamina papyracea or nasal septum.⁴ Through computed tomography (CT), it is often possible to assess the nasal and PNS anatomy with great detail.⁵ This has resulted in a greater interest in anatomical variants and their relationship with various diseases. One of the most prominent studies was the one conducted by Fadda et al.,⁶ where it was determined that various anatomical variants are associated with sinusitis.⁶ The present study sought to assess the frequency of variations in paranasal sinus anatomy in patients diagnosed with chronic rhinosinusitis at the Regional General Hospital No. 1 (RGH No. 1) of the Mexican Institute of Social Security (IMSS) in Tijuana, Mexico. Additionally, it wanted to determine the most frequent variation, number of variations per patient and the level of association of each variation.

A cross-sectional, retrospective, and analytical study was carried out in the RGH No. 1 of IMSS, a second-level hospital in the border city of Tijuana, Baja California, Mexico. A non-probabilistic sample was used, consisting of patients who underwent simple PNS tomography, referred by the otolaryngology service from January to June 2018. Inclusion criteria included: age ≥18, chronic rhinosinusitis diagnosis determined by an otorhinolaryngologist and simple PNS CT scan study. Patients with incomplete records or who were subjected to surgical treatments were excluded. After being authorized by the local research committee, the analysis of the radiology service database was performed, identifying the PNS tomographic studies and selecting those that met the inclusion requirements. The interpretation of the studies was performed by the main researcher (a radiology resident) and two independent radiologists. The degree of inter-observer concordance was estimated through the Cohen's Kappa statistical test. The studied variables were: age, gender, presence of septum deviation, affected side, involved sinus, and number and type of anatomical variations. The study was conducted in accordance with the 1964 Helsinki Declaration, Mexico's General Health Law regarding health research, as well as IMSS national guidelines. Due to its nature, signed informed consent was not required.

Descriptive statistics were used; qualitative variables were studied via measures of central tendency and measures of dispersion. Pearson's Chi Squared test was applied for a bivariate analysis and to estimate the predictability of association between age and gender with PNS variations. Data processing was performed with the SPSS statistical program.

After applying the inclusion and exclusion criteria, a total of 110 patients were identified; 58.2% (n=64) were women and 41.8% (n=46) were men. The most common age groups were 18-24 and 25-31 years old (Figure 1). Regarding the frequency of the anatomic variants of the PNS, nasal septum deviation was the most common anatomical variant (n=42, 38%), followed by a bullous shell (n=23, 20.9%). Prominent ethmoid bullas and paradoxical middle turbinates were the least common variants (each n=4, 3.6%) (Table 1). According to the side of occurrence, the left side had more cases (n=51, 46.4%), while 48 (43.6) cases were observed on the left side. There were 11 cases (10.0%) of bilateralism. It was observed that 40.9% (n=45) of the patients presented only one anatomical variant and 26.4% (n=29) two anatomical variations per patient; 20.0% did not show any variation (Figure 2). Within the female population, the most frequent variation was the nasal septum deviation (n=27, 42.2%), followed by pneumatization of the sphenoid sinus (n=11, 17.22%). Amongst male patients, the nasal septum deviation was also the most common variation (n=15, 32.6%), followed by bullous shells (n=14, 30.4%) (Table 2). Regarding the PNS variations by age, in the 18-24 and 25-31 age groups, the most common variations were deviated nasal septums and bullous shells. In the 32-38 age groups, deviated nasal septums and pneumatization of the sphenoid sinus were the most frequent finding. Among the 46-52 year olds, bullous shells and prominent agger nasi cells were common. A relationship between PNS variations and patient gender or age could not be established with the Chi-Squared test. Cohen's kappa coefficient was used to measure the degree of concordance of the observations done by the main researcher and two independent observers (radiologists). The results showed a high agreement rate. With the first radiologist, there was agreement in six variants; and with the second one, four (Table 3).

Figure 1 Patient distribution by age groups.

Figure 2 Number of PNS per patient.

Deviation of the nasal septum was the variation with the highest incidence in this population of patients with chronic rhinosinusitis, in addition to bullous shells and pneumatization of the sphenoid sinus, which coincides with the studies carried out by Fadda et al.,⁶ Ahmed et al.⁷ and Nobre et al.⁸ Increased prevalence of septal deviation with age was reported by Van der Veken, which can explain its higher prevalence, although other variations were more commonly identified in older patients. The study by Stallman et al.⁹ reported that bullous shells are related to the presence of sinusitis, though it did not increase the incidence of, specifically, chronic sinusitis. Though Fadda et al.⁶ established that rhinosinusitis has a high index of bilateral involvement, in our study, 90% had a unilateral involvement. As for the affected population, majority of patients were women between 18 and 24 years. Anatomical variations were typically found on the left side of the paranasal sinuses in this population sector. In contrast to the data presented by Braun et al.¹⁰ and the Nigerian Health Institution,¹¹ in the present study, the most frequent types of pneumatization of the sphenoid sinus were not established. In Mexico, only two studies have been done in the subject, one in the central and one in the southeast part of the country. Both describe characteristics of the most frequent anatomical variations, which they conclude are present in the middle, superior and supreme turbinate.^12,13 For future studies, a more thorough investigation into the relationship that the age factor has with the PNS variations could be done comparing pediatric and adult populations. Likewise, the degree of clinical involvement and the location of the anatomical variations should also be taken into account. This will provide more evidence for preventative measures or possible complications caused by this disease.¹⁴

The deviation of the nasal septum was the most frequent anatomical variation. Unilateral involvement was more frequent. The 18 to 24 and 25 to 31 age groups registered the most cases. Most of the patients presented only one variation. The results of Cohen's Kappa test showed a high rate of agreement regarding the PNS variations. A relationship between PNS variations and patient gender or age could not be established.

None.

Author declares that there is no conflict of interest.

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