Nasal septal deviation (NSD) is a frequent finding in both clinical and radiological examinations, with prevalence up to 89.2% in the general population.1 Patients with NSD-related nasal obstruction are often candidates for septoplasty.2 Surgical correction of the deviated nasal septum is the most frequent procedure performed in adults by otorhinolaryngologists.2–4 Recent epidemiological studies reported that 260,000 and 10,000−95,000 septoplasties are performed annually in the USA and European countries respectively.2,5–7

Clinicians and, more recently, health insurance companies have been searching for a diagnostic method that could serve as an objective indicator of the nasal obstruction severity, and thus strongly supporting the decision for septoplasty. Computed tomography (CT) was suggested as a method of choice to give detailed insight into the septum morphology and to provide one or more parameters that could potentially predict nasal obstruction severity. However, the few studies that correlated CT images and subjective nasal obstruction symptoms reported conflicting results about which morphological characteristics of the NSD, if any, should be recommended as an indicator of the symptom severity.8–10 Besides contradictory results, CT was used only for NSD angle and cross-sectional area measurement in the different parts of the nasal cavity. An advantage of the CT to show the detailed morphology of the deviated septum was not fully utilized. It is still unclear whether the complex morphology of NSD (e.g. spurs, S-shaped, “gutter” form) may have any influence on the subjective sensation of the nasal obstruction severity.

Although there are numerous classifications of NSD in clinical practice, Mladina's classification is considered the most detailed.1 This comprehensive classification includes complicated anatomical variants of the nasal septum usually omitted by other simplified classifications and divides NSD into seven types.1

This study aimed to investigate the association between nasal obstruction symptom severity assessed by the NOSE scale and CT morphology of NSD and the angle of NSD. Anatomical variants of the NSD, including spurs, S-shaped, and “gutter” form of NSD were classified according to Mladina's classification. An additional goal of the study was to estimate the prevalence of NSD in the Serbian population. We hypothesized that the morphology of the NSD may explain the severity of nasal obstruction symptoms and that patients with a higher angle of NSD have more severe nasal obstruction.

The prevalence of NSD in the adult population varies among different studies. In our sample, the prevalence of the NSD was slightly higher in comparison to previous studies. Similar inter-study differences in the NSD prevalence also exist in relation to gender and Mladina's types of NSD. A few authors have reported a slightly higher NSD prevalence in males.1,16,17 In our study, however, NSD was more commonly encountered in females (60.4%), although this gender difference was not statistically significant. This could be due to the higher number of females in the study sample because participants were consecutively enrolled as they came to the CT examination. Our results also showed a predominance of Mladina's type 7, type 5, and type 3 NSD in decreasing order (Table 2). By contrast, an international study conducted by Mladina et al.1 found type 3 as the most prevalent (20.4%), followed by type 2 (16.4%) and type 1 (16.2%). Type 7 in their sample was the least frequent.1 However, type 1 NSD has been the most frequently diagnosed in Koreans, Indians, and Saudi Arabs.16–18

Potential reasons for the significant discrepancy in NSD frequencies between studies might be due to different techniques used to diagnose NSD, and due to inter-study differences in target populations. Techniques such as anterior rhinoscopy and endoscopy were frequently-used diagnostic tools for NSD. The disadvantage of anterior rhinoscopy is that posterior parts of the nasal septum cannot be fully visualized, and consequently, some posterior deviations might be omitted. Therefore, it could be expected that studies in which anterior rhinoscopy was an examination technique of choice underestimate real prevalence of NSD. Although endoscopy allows visualization of the complete nasal septum, the angle of the NSD could not be measured with great accuracy and repeatability.9,19 Concerning the types of NSD, Mladina pointed out that type 5 can be easily overlooked by anterior rhinoscopy.1 A higher percentage of type 5 NSD in our sample could be explained by a more comprehensive evaluation of the nasal septum by CT.

Although CT is not recommended for routine NSD diagnosis and evaluation, it is superior to anterior rhinoscopy and endoscopy because it visualizes the whole septum in three planes. Thus, septal morphology can be carefully examined, the angle of NSD can be precisely measured, and none of the seven types of NSD can be misjudged. It also allows an accurate measurement of the nasal valve angle, which is essential for the differentiation between type 1 and 2 NSD. The CT assessment of the nasal valve angle could be the reason for a different frequency of type 1 and type 2 in the current study in comparison to other studies.

Previous studies that investigated NSD prevalence were conducted in ENT clinics where the number of patients that suffer from NSD can be significantly higher. Furthermore, it might falsely present harsh nasal obstruction symptoms in the majority of patients with NSD. However, it is well known that not all patients with NSD have nasal obstruction symptoms.2,8 Out of 225 patients in the current study, symptomatic NSD was recorded in 167 (74.2%) patients. Therefore, we focused on a normal unbiased population, who presented with a wide range of NOSE scores and CT morphology of the nasal septum. Patients were selected at the Department of Diagnostic Radiology in order to target the most general population. This way, a more representative sample was obtained by omitting ENT clinics and implementing well-defined exclusion criteria. Therefore, it was possible to accurately investigate the real presence and severity of NSD induced nasal obstruction and whether different morphological characteristics of NSD influence the nasal obstruction symptoms.

According to NOSE scores, there were measurable differences in nasal obstruction severity between seven types of NSD. Patients with type 2 NSD reported the worst NOSE scores. Since this result was obtained from only two patients, it could not be simply extrapolated to the general population. However, these were not the only cases with type 2 NSD. Almost one-third of the type 7 NSD cases consisted of type 2 and other types of NSD (23/77 patients). Their NOSE scores were also relatively high, but the mean NOSE score for type 7 NSD was lower. Our finding was in accordance with previous clinical studies as well as the airflow dynamics analysis of the nasal valve region.17,20,21 Many authors argue that deviation in the nasal valve area is critical for nasal obstruction and causes the most burdensome obstruction symptoms. The mechanism behind this was revealed in studies that evaluated nasal airflow resistance in experimental nasal models. Namely, it has been found that constriction in the valvular region results in a higher increase in airflow resistance than narrowing in the middle of the nasal cavity.21 If there is a combined narrowing in the nasal valve region and the middle nasal cavity (type 7 NSD in Mladina's classification system), the valvular deviation usually has a more significant impact on nasal obstruction.21 Similar to type 2, the nasal valve angle is also changed in type 1. Patients with this NSD type also reported more severe symptoms than other NSD types (Table 3). However, observed differences in NOSE scores between Mladina's types of the NSD were not statistically confirmed as significant. Such a result could be a consequence of a relatively low number of patients with type 1 and 2 NSD compared to the percentage of other NSD types. This finding may reflect a true low prevalence of isolated types 1 and 2 in our population and/or their coexistence with other types that constitute type 7 NSD.

Based on the NOSE scores, it seems that type 5 is also important for the severity of the obstruction in our patients (Table 3). The presence of a bony spur characterizes this type of NSD. Wee et al.17 reported that, after type 1 and 2, patients with type 5 NSD frequently complained of nasal obstruction, but the symptom severity was not quantified. In general, the impact of spurs on the nasal obstruction was under investigated. Simmen et al.22 observed turbulent flow in an experimental cadaveric model of the nose behind the spur. In the computational model of the nasal cavity, Liu et al.20 found complicated airflow and velocity distribution associated with a spur, but the results were not presented in the paper.

The association between the angle of the NSD and nasal obstruction is not clear. Ardeshirpour et al.10 found out that the angle of deviation measured at the anterior, middle, and posterior part of the nasal septum, as well as maximal angle, poorly correlate with NOSE scores. The same author also noticed a poor connection between the more obstructed side of the nose and the side of the deviation.10 The opposite conclusion was provided by Lee and his team9 who stated that the angle of NSD measured at the osteomeatal unit level has a significant impact on the subjective symptoms of nasal obstruction. However, the same author failed to detect any connection between nasal valve angle and obstruction symptoms.9 According to Savovic et al.,8 a NSD angle greater than 10° has a significant effect on the difficulty of breathing through the deviated side of the nose. In our study, the NSD angle ranged from 2.5° to 22.6°, but regression analysis did not show its significant effect on nasal obstruction. The fact that a slightly higher mean and maximum NSD angle was measured in patients without nasal obstruction symptoms supports this conclusion (Table 5).

The estimated prevalence of NSD in the Serbian population was high. The most common type of NSD was type 7, while the least frequent was type 2. Patients in the current study showed apparent differences in NOSE scores in relation to the type of NSD. Our results suggest that morphological characteristics of NSD expressed through the Mladina's classification and the NSD angle could not fully explain nasal obstruction severity.

The authors declare no conflicts of interest.