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Table of Contents
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 2  |  Page : 74-77

Prevalence of different types of sphenoid sinus pneumatization in the Indian population: A noncontrast computed tomography-based study


1 Department of Radiodiagnosis, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
2 Department of Pathology, Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India

Date of Web Publication18-Nov-2019

Correspondence Address:
Dr. Arshed Hussain Parry
Department of Radiodiagnosis, Sher-i-Kashmir Institute of Medical Sciences, Srinagar - 190 011, Jammu and Kashmir
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ami.ami_29_19

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  Abstract 

Background: Trans-sphenoidal approach for various surgical interventions of sella and suprasellar pathologies is fraught with the risk of injuring vital neurovascular structures which lie nearby. Preoperative knowledge of the pattern of sphenoid sinus pneumatisation is of paramount importance to anticipate and simultaneously undertake appropriate precautions to avert any complication. Objective: To determine the prevalence of different types of sphenoid sinus pneumatisation in our population. Materials and Methods: NCCT head images of 613 patients were analysed retrospectively to determine the type of sphenoid sinus pneumatisation. Individuals in the age range of 20 to 75 years were included in the study. Individuals with age less than 20 years (pneumatisation incomplete), previous surgery involving skull base/sphenoid sinus and trauma causing hemo-sinus/fractures around skull base or having space occupying lesions around skull base/sphenoid sinus were excluded from the study. Results: The age range of evaluated patients was 20 to 75 years with mean age of 45.67 years of which 368 (60.03%) were males and 245 (39.97%) were females. There was no significant statistical difference in the prevalence of various types of sphenoid sinus pneumatisation between male and female subjects (P-value >0.05). The commonest type of sphenoid sinus pneumatisation was post-sellar type (82.71%) followed by sellar (14.68%) and pre-sellar (2.45%) type. Conchal type was extremely rare. Conclusions: Preoperative computed tomographic (CT) evaluation of sellar region is a requisite whenever trans-sphenoidal surgery is contemplated to determine the location and extent of sphenoid sinus walls to shorten operative time and to minimize morbid consequences.

Keywords: Conchal, postsellar, presellar, sellar, sphenoid sinus pneumatization


How to cite this article:
Wani AH, Parry AH, Feroz I, Choh NA, Gojwari TA. Prevalence of different types of sphenoid sinus pneumatization in the Indian population: A noncontrast computed tomography-based study. Acta Med Int 2019;6:74-7

How to cite this URL:
Wani AH, Parry AH, Feroz I, Choh NA, Gojwari TA. Prevalence of different types of sphenoid sinus pneumatization in the Indian population: A noncontrast computed tomography-based study. Acta Med Int [serial online] 2019 [cited 2019 Dec 14];6:74-7. Available from: http://www.actamedicainternational.com/text.asp?2019/6/2/74/264366


  Introduction Top


Transsphenoidal approach for various surgical interventions of sella and suprasellar pathologies has witnessed an enormous rise with the advent of sophisticated endoscopic armamentarium.[1] The transsphenoidal route is currently employed for the endoscopic interventions for a host of sellar and suprasellar diseases. However, given the tricky location of sphenoid sinus at the base of the skull where it is nestled between various vital neurovascular structures, injuries to these vital structures is a peril of transsphenoidal surgeries. Leaking of cerebrospinal fluid is the most common reported complication. Injury to the optic nerve, cavernous sinus, internal carotid artery, or pituitary dysfunction are other commonly encountered complications.[2],[3],[4] Thus, preoperative knowledge of the pattern of sphenoid sinus pneumatization is of paramount importance to anticipate and simultaneously undertake appropriate precautions to avert such complications. Multiple classifications of the types of sphenoid sinus pneumatization exist. Many authors usually describe three types of sphenoid sinus pneumatization; conchal, presellar, and sellar.[5] Lang added the fourth type and named it postsellar where extension of the pneumatization was posterior to the sella turcica.[6] Noncontrast computed tomography (NCCT) with its ability to provide multiplanar reformations with sharp algorithms is now a reference standard for visualization of different types of sphenoid sinus pneumatization preoperatively. We undertook this study to determine the prevalence of various types of sphenoid sinus pneumatization in our population.


  Materials and Methods Top


This was a retrospective observational study where we analyzed the NCCT head images of 613 patients acquired in our accident and emergency computed tomography (CT) section for various indications between July 2017 and July 2018. Institutional Ethical Committee Clearance was obtained for the study. Individuals in the age range of 20–75 years were included in the study. Individuals with age <20 years (pneumatization incomplete), previous surgery involving skull base/sphenoid sinus, trauma causing hemosinus/fractures around the skull base, or having space-occupying lesions around skull base/sphenoid sinus were excluded from the study. On the CT workstation after retrieval of data from picture archiving and communication system (PACS), multi-planar coronal, sagittal, and axial reconstructions were performed. Reconstruction parameters were slice thickness 1.5 mm, recon increment 1.3 mm, the field of view 223 mm × 223 mm, window: osteo and kernel as H70s sharp FR (head 70 smooth sharp fast reconstruction). Analysis of CT images was done on a PACS workstation monitor by an experienced radiologist. For classifying sphenoid sinus pneumatization, vertical lines were drawn along the anterior and posterior walls of the sella. Conchal type was defined as absent pneumatization or pneumatization >10 mm anterior to the anterior wall of sella. In presellar type, the posterior margin of pneumatization was anterior to the anterior wall. In sellar type, the posterior margin of pneumatization extended beneath the sella but anterior to the posterior wall of sella. The posterior margin of pneumatization extended posteriorly to the posterior wall of sella in complete sellar or postsellar type.[7]

Statistical analysis

The data were analyzed using statistical software SPSS v 20 (statistical package for social sciences and STATA v 11 (statistics and data). Categorical variables were described in terms of frequency and percentage, and the continuous variables in terms of descriptive statistics such as mean and standard deviation. The value of P < 0.05 indicated a statistical significant difference in the Chi-square test.


  Results Top


We evaluated 613 head NCCTs retrospectively. The age range was 20–75 years with the mean age of 45.67 ± 15.44 years, of which 368 (60.03%) were male and 245 (39.97%) were female. There was no statistical significant difference in the prevalence of various types of sphenoid sinus pneumatisation between male and female participants (P > 0.05). The most common type of sphenoid sinus pneumatization in this study was postsellar type (82.71%) in both males (83.97%) as well as females (80.82%) [Figure 1]a, [Figure 1]b and [Figures 2]. Sellar type of sphenoid sinus pneumatization was the second-most prevalent type of pneumatization in the present study (14.68%) [Figure 3]. It was seen in 13.86% of males and 15.92% of females in this study. Presellar type of pneumatization was less common in this study (2.45%) [Figure 4]. It was seen in 2.17% of male participants and 2.86% of female participants. Conchal type was extremely rare. We came across only one case of the conchal type of sphenoid sinus pneumatization (0.16%) [Figure 5].
Figure 3: Sagittal noncontrast computed tomography images showing sellar type of sphenoid sinus pneumatization

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Figure 4: Sagittal noncontrast computed tomography images showing presellar type of sphenoid sinus pneumatization

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Figure 5: Sagittal noncontrast computed tomography images showing conchal type of sphenoid sinus pneumatization

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  Discussion Top


Sphenoid sinus pneumatization is hardly apparent at birth with early imaging evidence of pneumatization seen in children on NCCT as early as 2 years.[8] Pneumatization usually extends inferiorly and postero-laterally as age progresses with posterior-most limit up till spheno-occipital synchondrosis. Pneumatization progresses slowly and attains maturity usually by 20–25 years of age.[9] The volume of the pneumatized sphenoid sinus starts decreasing after the fourth decade reducing to two-thirds of its maximum volume by the seventh decade of life.[10] A widely used classification divides sphenoid sinus pneumatization into conchal, presellar, and sellar type.[11] This classification is helpful in planning the surgical tract to be used in transsphenoidal surgeries. Lang added the fourth type and named it postsellar where extension of pneumatization was posterior to the sella turcica.[6] It is similar to the classification by Güldner et al. who divided the sellar type into an incomplete and complete type based on the posterior extent of aeration beyond the posterior wall of sella.[12] All these classifications concentrate on the posterior extent of pneumatization and the ease of accessibility of the sellar floor during skull base surgeries. Rapid advances in the transsphenoidal sinus surgeries and its usefulness in accessing masses involving foramen magnum and the retroclival region has renewed the interest in studying the sphenoid sinus pneumatization patterns. Detailed preoperative NCCT imaging of sphenoid sinus and the sellar region is now a sine qua non for proper surgical approach to the skull base and prevent complications.[13] The postsellar type of pneumatization was the most common in this study seen in 82.71% of the participants followed by the sellar type seen in 14.68% of the population. Together these two patterns accounted for 97.39%. The reported incidence of the sellar type of sphenoid sinus pneumatization ranges in the literature from 59% to 86%.[9],[11],[14],[15] The present study is in concordance to the world literature; however, the incidence of postsellar pneumatization was higher than the world literature in this study (P < 0.05). The incidence of presellar pneumatization was 2.45%, which was significantly less than the percentage reported in the world literature (P < 0.005).[9],[13],[14],[15],[16] We came across only one case of the conchal type of pneumatization in this study. Conchal pneumatization was considered unfavorable for a transsphenoidal approach to the parasellar area. With the availability of high-speed drills, it is not now considered a contraindication for the transsphenoidal approach. Availability of intraoperative navigation after documentation of surgical landmarks on preoperative imaging makes access to sella safe.[17],[18] No bulge of the sellar floor into sphenoid sinus occurs in presellar type.[19] The anterior wall of sella can be easily approached, but in order to expose the base of sella, clivus has to be drilled. Pneumatization extends beyond the sellar region into the sphenoid body reaching up to clivus in sellar and postsellar types. This makes removal of posterior wall easy allowing complete exposure of sellar base during transsphenoidal surgeries.[9] Pneumatization can be extreme in sellar and postsellar types extending laterally to the carotid canals and optic nerve. Further studies are needed to fully elucidate the nature of overlying covering of these vital neurovascular structures (whether thin bone or absent covering) to carefully plan transsphenoidal surgeries and prevent any catastrophe.[20]

Summarizing, the preoperative CT evaluation of the sellar region is a requisite whenever transsphenoidal surgery is contemplated to determine the location and extent of sphenoid sinus walls, to shorten the operative time, and to minimize morbid consequences. The extent of pneumatization of sphenoid sinus should be included in routine reporting templates of head CT in patients where the transsphenoidal approach is mulled over. This study also shows a significantly higher incidence of postsellar pneumatization of sphenoid sinus in our population, thereby suggesting ethnic variation in sphenoid sinus pneumatization being a rule rather than an exception. Further studies are also needed to determine the prevalence and degree of the lateral extension of sphenoid sinus pneumatization to minimize injuring vital neurovascular and glandular structures during transsphenoidal surgeries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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[PUBMED]  [Full text]  
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Carter LC, Pfaffenbach A, Donley M. Hyperaeration of the sphenoid sinus: Cause for concern? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88:506-10.  Back to cited text no. 9
    
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Yonetsu K, Watanabe M, Nakamura T. Age-related expansion and reduction in aeration of the sphenoid sinus: Volume assessment by helical CT scanning. AJNR Am J Neuroradiol 2000;21:179-82.  Back to cited text no. 10
    
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Hammer G, Radberg C. The sphenoidal sinus. An anatomical and roentgenologic study with reference to transsphenoid hypophysectomy. Acta Radiol 1961;56:401-22.  Back to cited text no. 11
    
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Güldner C, Pistorius SM, Diogo I, Bien S, Sesterhenn A, Werner JA. Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT). Acta Radiol 2012;53:214-9.  Back to cited text no. 12
    
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Zada G, Agarwalla PK, Mukundan S, Dunn I, Golby AJ, Laws ER Jr. The neurosurgical anatomy of the sphenoid sinus and sellar floor in endoscopic transsphenoidal surgery. J Neurosurg2011;114:1319-30.  Back to cited text no. 17
    
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Nomikos P, Fahlbusch R, Buchfelder M. Recent developments in transsphenoidal surgery of pituitary tumors. Hormones (Athens) 2004;3:85-91.  Back to cited text no. 18
    
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Kayalioglu G, Erturk M, Varol T. Variations in sphenoid sinus anatomy with special emphasis on pneumatization and endoscopic anatomic distances. Neurosciences (Riyadh) 2005;10:79-84.  Back to cited text no. 19
    
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]



 

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