|Year : 2019 | Volume
| Issue : 3 | Page : 143-147
Classification of anatomical variants of maxillary sinus shapes and symmetry using computerized tomographic imaging
Abdulhameed Aliu1, Ma’aji S Mohammad2, Bello S Sirajo1, Ahmad M Ibrahim1, Zagga D Abdullahi1
1 Department of Anatomy, College of Health Sciences Usmanu Danfodiyo University, Sokoto, Nigeria
2 Department of Radiology, Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria
|Date of Submission||29-Jul-2019|
|Date of Decision||04-Nov-2019|
|Date of Acceptance||17-Dec-2019|
|Date of Web Publication||04-Feb-2020|
Dr. Abdulhameed Aliu
Department of Anatomy, Faculty of Basic Medical Sciences College of Health Sciences, Usmanu Danfodiyo University, PMB. 2346, Sokoto
Background: The maxillary sinus is characterized by a considerable variation in sizes and shapes and between the right and left sides. Due to easy access to all its walls and surfaces, imaging via computerized tomography (CT) has enhanced the quality and quantity of information obtainable from the assessment of the maxillary sinus. Aim: To determine normal variations in shapes and symmetry of the maxillary sinus using CT. Methods: A total of 130 subjects comprising 79 males and 51 females, between the ages of 20 and 80 years, with normal maxillary sinus CT anatomy, who had head CT scans carried out at the Radiology Department of the Usmanu Danfodiyo University Teaching Hospital (UDUTH) Sokoto, over a period of five years, were used for this study. Images were taken with a GE Bright Speed Multidetector Helical CT (GE Healthcare, USA, 2005) Scanner, while films were viewed on the computer monitor. Variations in shapes of the maxillary sinus were identified on axial images and classified based on their resemblance to known shapes of solids. Data were analyzed using Minitab 16.0 statistical package (Minitab inc. USA). Results: Five distinct shapes of the maxillary sinus were identified. These were: irregular in two subjects (0.77%) (right = 1 and left = 1); oval in three subjects (1.15%) (right = 2 and left = 1); quadrangular in three subjects (1.15%) (right = 2 and left = 1); spherical in 61 subjects (23.46%) (right = 30 and left = 31); and triangular 191 (73.46%) (right = 95 and left = 96). Shapes were symmetrical in 85.38% and asymmetrical in 14.62% of subjects. Conclusion: Five normal but distinct shapes of the maxillary sinus were identified, with the predominant shape, being the triangular type, and sinuses of individuals were frequently symmetrical in shape.
Keywords: Anatomical variations, computerized tomography, maxillary sinus, shapes, symmetry
|How to cite this article:|
Aliu A, Mohammad MS, Sirajo BS, Ibrahim AM, Abdullahi ZD. Classification of anatomical variants of maxillary sinus shapes and symmetry using computerized tomographic imaging. Sub-Saharan Afr J Med 2019;6:143-7
|How to cite this URL:|
Aliu A, Mohammad MS, Sirajo BS, Ibrahim AM, Abdullahi ZD. Classification of anatomical variants of maxillary sinus shapes and symmetry using computerized tomographic imaging. Sub-Saharan Afr J Med [serial online] 2019 [cited 2020 Jul 5];6:143-7. Available from: http://www.ssajm.org/text.asp?2019/6/3/143/277781
| Introduction|| |
The maxillary sinus occupies the cavity of the maxilla; it is the largest of the paranasal sinuses and represents a complex anatomical structure with a significant intra and inter-individual variation., It is characterized by a considerable variation in size and shape and between the right and left sides.,,, The maxillary sinus reaches its matured size at the age of 20 years, when the permanent teeth fully develops. This development is associated with changes in the extent of pneumatisation, and as a result, its shapes and sizes. Genetic and environmental factors, in addition to adjacent cartilages and bony facial structures may influence this developmental process, , as such, a detailed knowledge of the anatomy of the sinuses is critical in performing procedures such as functional endoscopic sinus surgery. , Computerized tomography (CT) has improved the quality and quantity of available information, derivable from the assessment of the maxillary sinus, which are not directly visible using other radiologic procedures like the x-ray, and this is increasingly becoming important, especially among anthropologists and paleopathologists.,
The shapes of the maxillary sinus were classified into triangular, oval, curved, rectangular and square shapes, according to Lerno,  while Szilvassy  classified the shapes of its base into; triangular, leaf, scapular and renal shapes. In the report of Donal et al., ten out of twelve models of cadaveric specimens showed a 3-walled pyramid, different from the classical 4-sided pyramid, whereas, the triangular sinuses were the most common among Turkish population. Maryam et al.  reported 17% sinus asymmetry, and 83% of symmetric morphology with small differences at some levels in the sinus outline, whereas sinus asymmetry was 100%, among Southwestern Nigerians, using dry adult crania. There is paucity of data on the classification of normal anatomical shapes of the maxillary sinus using CT among Nigerians (Africans), majority of the studies mentioned above, were conducted among Caucasian subjects. Information on the shape classification and symmetry of the maxillary sinus will be useful to maxillofacial surgeons and otolaryngologists, who, during certain procedures employ the use of endoscopes in the presence of limited sinus visibility. The aim of this study was therefore, to compliment these few studies and to establish baseline data for values in our environment.
| Materials and methods|| |
This retrospective study was carried out at the Radiology Department of the Usmanu Danfodiyo University Teaching Hospital (UDUTH) Sokoto, with the approval of the institutional ethical committee. This study was conducted on head CT scans of 130 subjects (79 males and 51 females), between the ages of 20 and 80 years, with normal maxillary sinus CT anatomy, over a five-year period, from April 2013, to March 2018. Images were taken with a GE Bright Speed Multidetector Helical CT (GE Healthcare, USA) scanner, (2005 model, 15 cm FOV, 200 mA, 120 kV, scanning at high resolution bone algorithm at 1 second and slice thickness of 5 mm). CT scans that demonstrated maxillary sinus disease, subject ages of less than 20 years, craniofacial abnormalities, mid-facial traumatic injuries, and tumors were excluded. The CT images were viewed on the computer monitor, and screened to assess if subjects were properly positioned prior to scanning, to ensure sinus symmetry. This was checked on the scout image by ensuring that, both rami and angles of the mandible were aligned, the tips of the mastoid processes and the alveolar margin of the maxilla, were on the same plane, while, the upper margin of the zygomatic bone, and the inferior orbital rim, are on the same horizontal plane. Only axial films were used because coronal images had a disadvantage of being distorted by metal artefacts from tooth filling, and the fact that sinus outline on this plane appear basically the same. Variations in shapes of the maxillary sinus were identified at mid-sinus planes corresponding to the lower border of the zygomatic arch, roots of the pterygoid plates and floor of the sphenoid sinus. These shapes were subsequently classified on the basis of their resemblances to shapes of known solids into Irregular, Oval, Quadrangular, Spherical, and Triangular. Symmetry of the maxillary sinus was resolved on the basis of the similarity in shapes between the right and left sinuses. Data was manually sorted out, tabulated, then, entered into computer using Microsoft Excel, data analysis was done using Minitab 16.0 statistical package (Minitab inc. USA), while comparison was done using chi square tests [Figure 1],[Figure 2],[Figure 3],[Figure 4],[Figure 5],[Figure 6].
|Figure 1 Axial CT of a 27 year old female showing the spherical shape (arrows) of the maxillary sinus. R = Right side, L = Left side, A = Anterior, P = Posterior.|
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|Figure 2 Axial CT section of a 38 years old female showing asymmetry of the maxillary sinus. The right side is oval (long arrow) while the left side is quadrangular (short arrow). R = Right side, L = Left side, A = Anterior, P = Posterior.|
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|Figure 3 Axial CT of 44 years old male showing the quadrangular type (arrows) of maxillary sinus shape. R = Right side, L = Left side, A = Anterior, P = Posterior.|
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|Figure 4 Axial CT of a 65 years old male with an irregular type (short arrow) of sinus shape on the right maxillary sinus and triangular type (long arrow) on the left. R = Right side, L = Left side, A = Anterior, P = Posterior.|
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|Figure 5 Axial CT of a 42 year old female showing a triangular shaped maxillary sinus (arrows). R = Right side, L = Left side, A = Anterior, P = Posterior.|
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|Figure 6 A pie chart showing the frequency of the observed shapes of the maxillary sinus.|
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| Results|| |
The variations in normal anatomical shapes of the maxillary sinus on axial CT slides seen in this study were five distinct shapes. These were; Irregular in 2 subjects (0.77%); (right = 1 and left = 1), Oval in 3 subjects (1.15%); (right = 2 and left = 1), Quadrangular in 3 subjects, (1.15%); (right = 2 and left = 1), Spherical in 61 subjects (23.46%); (right = 30 and left = 31), and Triangular 191, (73.46%); (right = 95 and left = 96). There was no significant relationship between males and females, in the number of subjects who had a particular sinus shape [Table 1], [Table 2]. The predominant shape of the maxillary sinus in the studied population was triangular.
|Table 1 The relationship between observed anatomical shapes of the maxillary sinus and sinus location with respect to right or left sides|
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|Table 2 The relationship between symmetry or asymmetry of the maxillary sinus and sex of subjects used in the study|
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With respect to the incidence of symmetry and asymmetry between the right and the left sides, in the shapes of subjects’ maxillary sinus, this study found that, 111 subjects (85.38%), accounting for 64 males, (49.23%) and 47 females, (36.15%), had symmetrical sinus shapes, while sinus asymmetry was found in 19 subjects (14.62%), in which 15 (11.54%) were males and 4 (3.08%) were females. There was a statistically significant relationship between sinus shapes and gender, P < 0.05 [Table 2].
| Discussion|| |
The several findings regarding the complex nature of maxillary sinus anatomy emanating from different studies is a reflection of the influential effects of human variability and the different degrees of pneumatisation., In this study, five distinct shapes of normal human maxillary sinus were observed on axial CT scans with the predominant shape being triangular. This favorably agrees with the report of Gunay et al., although, in another report, shape classification of the maxillary sinus was unsuccessful , possibly because, they aimed at classifying only the medial wall of the sinus using dried crania. The reasons for these differences are unknown, however, these may be due to the influence of environmental, genetic, ethnic or racial factors.Several other authors have classified the shapes of the maxillary sinus into other natural shapes like the leaf, scapular, renal and solids of evolution, for comparison and resemblances.,,
In this study, the occurrence of shape symmetry or asymmetry, between the right and left sides, showed that, the maxillary sinus among Northwestern Nigerians were frequently symmetrical (85.38%). This result is in agreement with the findings of Maryam. However, Amusa et al. reported sinus asymmetry in 100% of the 24 dried human skulls from Southwestern Nigeria. These differences could also possibly have resulted from the differences in the methods that were applied, environmental, ethnic, or genetic factors.
Clinically, this information is valuable, and could be applied in preoperative assessment to determine a safer and easy access to the pterygopalatine fossa through the maxillary sinus.
| Conclusion|| |
CT examination of the maxillary sinus is valuable, and supportive in investigating variations of the maxillary sinus for a wide range of surgical, clinical and anthropological significance. From this study, five normal, but distinct shapes of the maxillary sinus were identified, the triangular type was predominant, while these sinus shapes were frequently symmetrical between the right and left sides.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2]