Pneumatization Types of Sphenoid Sinus
Even less is known about genetic and environmental factors that may influence the pneumatization process: some authors suggest that nasal airflow and positive air pressure in the nasopharynx can alter the pneumatization of the paranasal sinuses as well as the morphology of the nasal opening. Other theories consider opportunistic expansion of the epithelium versus the structural configuration of the bone: finally, genetic and pathological factors are taken into account, although their weight in determining pneumatization still needs to be determined [24].
In some studies, it was observed that three types of sphenoid sinus pneumatization were defined as sellar, presellar and conchal type. Sellar type pneumatization was classified as the type reaching posterior to the tuberculum sella[5]. In these reviewed studies [9, 25–28], the most common type was reported to be the sellar type, with a prevalence ranging from 58.7–93%.
Degaga et al.[29] reported the conchal, presellar, sellar and postsellar type prevalence as 2%, 25.5%, 50% and 22.5%, respectively. In the study of Battal et al.[30], conchal, presellar, sellar and postsellar type prevalence was reported as 1%, 18.2%, 12.7% and 68.2%, respectively. Tomovic et al.[31] reported that conchal, presellar, sellar, and postsellar type percentage were 1.8%, 7.3%, 47.6%, and 43.3%, respectively.Movahhedian et al.[4] reported the percentages of the conchal, presellar, sellar, postsellar (a), and postsellar (b) types as 1%, 11.5%, 35.5%, 38.9%, and 13.1%, respectively. Our results with a higher prevalence of postsellar type were generally compatible with the literature.
OC Prevalence
In the reviewed studies, the prevalence of OC was reported to be 8-65.3% [4,11–13,16,25, 27,28,32).
In this study, the prevalence of OC was found as 28.7% The difference between these rates is due to the fact that OCs are better detected in studies in which axial sections are examined, whereas OCs can be considered as posterior ethmoid cells in coronal section examinations [28].
Protrusion and Dehiscence of ICA
Movahhedian et al. [4] reported the prevalence of ICA dehiscence as 42.8%. Hewaidi etal.[21]reported that protrusion of ICA was observed in 41% of cases, of whom 22.7% were bilateral, 11.3% were right sided, and 7% were left sided. Dehiscence of ICA was observed in 30% of cases, of whom 10.3% were bilateral, 14.3% were on the right, and 5.3% were on the left. Erdoğan et al.[28] reported that the prevalence of ICA protrusion and dehiscence were 45.8% and 2.5%, respectively. Li et al.[33] reported the unilateral and bilateral protrusion as 8.68% and 20.57%, respectively. In the study of Turna et al.[34], protrusion and dehiscence of ICA were observed in 3% and 24 0.5% of the subjects, respectively. Parvathy et al.[35] reported that protrusion of ICA was found in 23.3% of cases (19M; 16F), of whom 42.9% were bilateral, 34.3% were right sided and 22.9% were left sided. Dehiscence of ICA was seen in 4% of cases (2M; 4F) of whom 50% were bilateral, 16.7% were on the right and 33.3% were on the left. In the study of Anusha et al.[26], the rates of ICA dehiscence and protrusion were 3.0 and 10.0%, respectively. Fadda et al.[9] reported the protrusion and dehiscence of ICA as 26.3% and 0.4%. In 1.1% of the cases, the ICA was dehiscent and protruded simultaneously. In the study of Singh et al.[36], protrusion and dehiscence of ICA was observed in 28% (16% M; 12% F) and 9% (3% M; 6% F) of cases. Dündar et al.[37] reported the prevalence of ICA protrusion as 27.9%. Davoodi et al.[38] reported that the protrusion and dehiscence of ICA in 48.5% and 39% of males, 34.3% and 44.9% of females, respectively. In this study, the prevalence of ICA protrusion and dehiscence was found as 40.7% and 40.7%, respectively.
Protrusion and Dehiscence of ON
In the study of Fadda et al.[9], the protrusion and dehiscence rate of ON were 13% and 1.5%, respectively. Hewaidi et al.[21] reported the prevalence of ON protrusion as 35.7%. Protrusion was seen as bilateral (20.3%), right sided (7%), and left sided (8.3%) of cases, respectively. Dehiscence of ON was noticed in 30.7% of patients, of whom 10% were bilateral, 12.3% were right sided, and 8.3% were left sided. Parvathy et al.[35] reported the prevalence of ON protrusion as 27.3% (24M; 17F), of whom 78%, 14.6% and 7.3% were bilateral, right sided and left sided, respectively. Dehiscence of ON was seen in 4% of cases (5M; 1F) of whom 50%, 33.3% and 16.7% were bilateral, right sided and left sided, respectively.Lupascu et al.[25], Anusha et al. [26], Li et al. [33] and Dündar et al.[37] reported the prevalence of ON protrusion as 65%, 2.3%, 16% and 17.8%, respectively.Movahhedian et al.[4] and Anusha et al.[26] reported the prevalence of ON dehiscence as 64.5% and 7%, respectively. Singh et al.[36] reported the rate of ON dehiscence as 29% (18% M; 11%F). Bilateral dehiscence of ON was more common than unilateral. In this study, the prevalence of ON protrusion and dehiscence was found as 28.7% and 81.3%, respectively.
Davoodi et al.[38] reported that the protrusion and dehiscence of ON in 38% and 28.5% of males, 34.9% and 46% of females, respectively.
The Volume and Surface Area of Sphenoid Sinus and Its Relation to Other Parameters
Singh et al.[36] reported that the average volume and diameterwas 6576.92mm3and 30.48 mm, respectively. The sinus volume was larger in males than in females. Sinus volume was significantly associated with gender and sinus condition. In the study of Sentürk et al.[32], total sinus volume was found to be 15.07 cm3 in cases without OC. They stated that total sinus volume was significantly lower in the cases with bilateral OC than without OC. In unilateral OC cases, a significant reduction in sinus volume was seen only for the side with OC. Similarly, Nomura et al.[39] reported that presence of OC reduces the volume. Li et al.[33] reported that the volume depended upon the protrusion degree in sinus and showed statistical differences. The volume of11.16, 14.2 and 25.03 cm3 was measured in cases without ICA protrusion, with the unilateral protrusion, and the bilateral protrusion, respectively. Gibelli et al.[40] reported that the total sinus volume was 10.005 cm3 and 7.920 cm3 in males and females, respectively. Presellar type showed the least sinus volume while the retrosellar type had the highest volumes.In this study, the sphenoid sinus with postsellar b type had the highest volume while conchal type had the least volume. Similarly, for all types, males showed higher volumes than females in this study.
In the study of Orhan et al.[41], the median sinus volumes were 4.40 cm3 on the right and 4.20 cm3 on the left. This study stated the mean volume and area of sinus were 9949.4 ± 351.0 mm3 and 4570.9 ± 1604.9 mm2, respectively.
Cohen et al.[42] stated that that the volume of sphenoid sinuses decreases with age.Oliveira et al.[43] suggests possible application for gender diagnosis based on the dimorphism of the sphenoid sinuses, although there was no statistically significant differences between males and females in their study. However, Cohen et al.[42] stated sexual dimorphism in sphenoid sinus size. Similarly, in our study, it was observed that there was a decrease in sinus volume and area with increasing age.
Along with the evaluation of sinus wall thickness and protrusion of surrounding noble structures, one of the most relevant information in surgery is the volume of the sphenoid sinuses [44]. However, volume is also one of the most difficult parameters to calculate [40].In recent years, the introduction of automatic and manual segmentation in CT scans has enhanced research in this area, allowing operators to easily obtain 3D models of anatomical structures and calculate volumes and areas[45]. Although semi-automatic segmentation is faster, manual segmentation is widely used in endoscopic surgery for computer and robotic assistance [45, 46].Due to its widespread use, we preferred to use the manual segmentation module in this study.