Radiological middle turbinate variations and their relation to nasal septum deviation in asymptomatic adult

Abstract

Background

Middle turbinate (MT) is one of the important anatomical and physiological structures of the nasal cavity. After the widespread use of nasal endoscope and paranasal sinus computed tomography (CT), many MT variations have been described. This study aimed to determine the incidence of MT variations by computed tomography (CT) in asymptomatic adult, their relation to each other, and to deviated septum (DS).

Results

In the included 86 subjects (172 MTs), pneumatized MT was the most common MT variation followed by paradoxical MT (PMT). Septal deviation did not appear to affect occurrence of pneumatized or PMT. Fifty-nine percent of the reported bilateral PMT were associated with pneumatized MT, while 35.7% of unilateral PMT were associated with pneumatized MT with non-significant difference.

Conclusion

MT variations in adults are common mainly pneumatized MT then PMT with no apparent relation to septum deviation.

Background

Middle turbinate (MT) is one of the important anatomical and physiological structures of the nasal cavity. MT shares in regulation of airflow and temperature, airflow filtration, and olfaction [1]. After the widespread use of nasal endoscope and paranasal sinus computed tomography (CT), many MT variations have been described such as paradoxically curved MT, pneumatized MT, secondary MT, and accessory and furcated MT [2]. The position and relationship of the MT to other important nasal structures is extremely important especially for pathogenesis of sinusitis, headache, and nasal obstruction, as well as, for endoscopic sinus and skull base surgery [3]. Concha bullosa (CB), the pneumatization of the concha, represents one of the most common sinonasal variations. Pneumatization of the concha is classified based on its location as bulbous CB, lamellar CB, and extensive CB [4]. A paradoxical MT (PMT) refers to an inferomedially curved MT edge with the concave surface facing the nasal septum [5]. PMT alone can lead to narrowing of the middle meatus up to obstruction of the ostiomeatal complex and interference with the physiological drainage of paranasal sinuses. In cases associated with bulbous MT, PMT potentially causes nasal obstruction [5]. The accessory MT is defined as a medially inclined uncinate process which may give the impression that two MTs are presented [6]. The secondary MT (SMT) is a bony structure in the middle meatus that originates from the lateral nasal wall. It is similar to the turbinate bone, and such variation is not related to osteomeatal obstruction and, therefore, it is not usually considered as a predisposing factor for sinusitis [7]. Furcated MT is a rare variant in which the turbinate splits into two (bifurcate) or three (trifurcate) divisions, giving the appearance of two or three MTs [8]. Study of these anatomical variations can assist in better understanding pathogenesis of infectious sinonasal diseases and increase the effectiveness and safety of endoscopic sinus surgery. This study aimed to determine the incidence of MT variations by CT in asymptomatic adult and their relation to each other and to deviated septum (DS).

Methods

This study was conducted in otorhinolaryngology and radiodiagnosis departments from July 2017 to January 2019. All participants were selected from subjects referred to CT examination of the head for different causes (brain, parotid gland, tempero-mandibular joint, and the mandible). CT examination of the nasal cavity was done as a part of the requested investigation, or additional selected cuts were applied after the first one.

Included subjects were asymptomatic adult (as regard nose and paranasal sinuses) without nasal pathology after proper history taking and clinical and CT examination. They were referred to as normal adult in the current study.

Informed written consent was signed by all subjected to contribute in the current study after explanation of our purposes. Subjects under the age of 16 years, patients with sinonasal disease, or patients who had previous sinonasal surgery or trauma were excluded from our study.

All CT examinations without using nasal decongestants were performed with a 64-multi-slice CT scan (Light speed volume VCT, GE medical system, Milwaukee, WI, USA). The protocol of MDCT was performed with a detector width 0.625 mm, a section width 1.5 mm, and 0.5 mm reconstruction interval.

Axial images were performed while the subject was in supine position, and the beam was parallel to the subject hard palate. The cuts began from the hard palate to the top of the frontal sinus (glabella), using 130 kV and 150 mA/s and wide window (Window widths (WW) about 1300 to 2000 and window levels (WL) about − 80 to − 200). High resolution algorithm was used for the enhancement of fine bony details.

Multiplanar reconstructions (MPR) with delicate details in the coronal and the sagittal planes for all subjects were post-processed at a dedicated workstation (Advantage Windows Volume share 4.5, GE Medical System, Milwaukee, WI, USA). Films were revised in the routine standardized fashion by one radiologist to confirm that small details were not missed. Each of the authors evaluated the CT cuts on all views in separate sessions and any discrepancy in evaluation was resolved and confirmed by the two radiologists.

Statistical analysis was performed using the SPSS statistical software package (version 18.0; SPSS, Inc., Chicago, IL, USA). P value of less than 0.05 was considered statistically significant.

Results

Eighty-six Egyptian adult subjects (172 MTs) were included in the current study with a mean age of 31.7 ± 10.5 (range 22–54), 54 females (63%) and 32 male (37%).

The reported variations of the MT are detailed in Table 1. Pneumatized MT was the most common MT variation detected and more than half of them were concha bullosa (51.1%) while extensive (total) conchae were not detected bilaterally in any of our cases. PMT was the second most common detected variation that was found bilaterally in most cases (76%) (Table 1) (Figs. 1 and 2).

Table 1 Incidence of middle turbinate variations

Fig. 1

Coronal CT scans of different pneumatized middle turbinate. a Left concha bullosa, b bilateral concha bullosa, c left total concha bullosa, d lamellar concha bullosa

Fig. 2

Coronal CT different paradoxical middle turbinate (PMT). a Left PMT, b right PMT, c right PMT and left total concha bullosa

Most concha bullosa and paradoxical MT were present with central septum. Concha was reported only in the same side of DS in 6 cases (3 concha bullosa, 2 lamella, 1 total), while concha was only documented in the contralateral side of DS in 6 cases (3 conchae bullosa, 2 lamella, 1 total). So DS did not appear to affect conchae (Table 2).

Table 2 Relation between septal deviation and MT variations

PMT was registered in the same side of the DS in 2 left sides and found in the contralateral side of the DS in two nasal sides (1 right and 1 left), so DS did not appear to affect PMT (Table 2).

Regarding relation of MT variations to each other, from the reported 22 bilateral PMT, 13 (59%) of them were associated with pneumatized MT. While of the 14 unilateral PMT, 5 (35.7%) were associated with pneumatized MT. But this difference was found non-significant (X² = 1.87, p = 0.171475) (Table 3).

Table 3 Multiple MT variations in the same subject

Discussion

The advances in CT scanning and the wide spread of endoscopic sinus surgery increased the detection of MT variations. MT variations include CB, PMT, and secondary and accessory MT. These variations and their relationship to DS may be a source of obstruction of the middle meatal and subsequent headache and rhinosinusitis [9].

CT represents the gold standard diagnostic tool for the nasal and PNS pathologies, and multiple advanced techniques [10] are utilized now in pre-management of different nasal and PNS pathologies. Knowing detailed knowledge of the anatomical variants of the nasal turbinates is critical for effective and safe surgical procedures especially during functional endoscopic sinus surgery.

In current study, MT variations were studied using MSCT in asymptomatic adults with pathology-free nose and paranasal sinuses. The most frequent MT variation was concha bullosa (51.1%), followed by PMT (33.7 %), while the least frequent reported MT variation was bifid MT in one adult. The CB incidence was previously reported to range from 14 to 53% [11] and reaches up to 73% [12]. In current study, the incidence of frequency of types of CB was determined as 20.9% for bulbous concha, 11.6% for lamellar Concha, and 8.1% for total conchae. San et al. [11] have reported higher frequency of CB types such as 46.95% for total conchae, 32.17% for bulbous concha, and 20.86% for lamellar Concha. The differences could be attributed to racial difference and the analytical methods used. Frequencies of pneumatized MT and PMT in previous reports were 28% and 25% for Japanese [13], 24.5% and 10% in Spain [14], 29% and 11% in Italian [15], 18.2% and 14.3% in Pakistani [16], and 31.1% and 7.5% in Nigerian subjects [17]. Environmental factors and genetics seem to be the attributed explanation for these variations.

In present study, prevalence of PMT was 33.7%, and it was bilateral in 76% of the affected sides. Riello and Boasquevisque [12] and Fikre et al. [18] noted lower prevalence rate of 29% and 26.1%, respectively.

Association of multiple MT anatomical variations was more with bilateral PMT and CB. Fifty-nine percent of the reported bilateral PMT was associated with pneumatized MT, while 35.7% of unilateral PMT were associated with pneumatized MT with non-significant difference. Some reports have suggested a relationship between the presence of a CB and DS, Tiwari et al. [19] found a strong relationship between the presence of a concha (a dominant or unilateral concha) and DS; in the other side, Vincent and Gendeh [20] disproved that DS is associated with CB in its development and pathogenesis of chronic rhinosinusitis.

Our study also showed no significant association between the most common MT anatomical variation as CB and PMT and the presence of ipsilateral or contralateral DS, so our study considered that CB and DS are coincidental variations.

The presence of these variations in our study in normal adult without rhinosinusitis may mean that no specific association of anatomic variations of MT and rhinosinusitis. This supports the hypothesis that local, systemic, environmental factors or intrinsic mucosal disease may be more significant in the pathogenesis of rhinosinusitis.

We used 64 MDCT, and application of such high multi-detector CT scanners or with higher detectors improve the image qualities [21, 22]. The effective radiation dose used during sinus MDCT is 0.5–0.9 mSv [23]. But, the familiarity with scanning parameters affecting the radiation dose and increased radiologists awareness are mandatory to achieve the highest image quality with the least exposure.

To the best of our knowledge, this is the first work describing the anatomical variations of the MT in Egyptian asymptomatic adult. Further studies are needed to compare such MT variation in different nasal pathologies and to compare between symptomatic and asymptomatic patients to assess the actual effect of these anatomical variants upon the clinical manifestation of the patients.

Conclusion

MT variations in adults are common mainly pneumatized MT then PMT with no apparent relation to septal deviation.