Anatomical variations of the sphenoid sinus and its adjacent structures: a review of existing literature

Anatomical variation in the sphenoidal sinuses in patients with chronic rhinosinusitis: A CT scan study

Computerized tomography (CT) of the skull base region has become an indispensable tool for endoscopic sinonasal surgery.

Objectives

Fundamental knowledge of the sinus anatomy is crucial for preoperative surgical planning. The aim of this research was to evaluate associations between the anatomical variations sphenoidal sinuses and chronic rhinosinusitis (CRS) by using CT.

Methods

A descriptive study was performed on patients with CRS, who were referred to the department of radiodiagnosis and imaging for CT scanning. Parameters were compared between the study and control groups.

Results

Among the anatomical variations, the presence of bilateral accessory septa within the sphenoidal sinus, and dehiscence and protrusion of the internal carotid artery and optic nerve (ON), were high in men and women in the case group compared with the control group. Among the anatomical variations in the sinonasal region of the male participants, a significant association (p < 0.05) was observed with ON protrusion and ON dehiscence. ON protrusion (OR = 2.168) in men was associated with elevated risk of CRS in the study population.

Conclusion

Knowledge of the anatomical variations in the sphenoid sinuses enables better understanding of the limits of surgical dissection during the treatment of sphenoid sinus surgeries.

Tips and Tricks to Safely Perform an Endoscopic Endonasal Trans-Sphenoidal Pituitary Surgery: A Surgeon's Checklist

The authors aimed to develop an extensive preoperative checklist of CT scan findings during endoscopic access to the ventral skull base and implement it in clinical practice. A comprehensive literature review was conducted to identify the radiological landmarks crucial to endoscopic skull base surgery. Four electronic databases were searched: PubMed, MEDLINE, EMBASE, and Google Scholar using search terms/keywords such as "radiological landmarks," "endoscopic skull base surgery," "CT scan," "pituitary surgery," "anatomical variations," "internal carotid," "optic nerve," "sphenoid sinus," "pneumatization," "dehiscence," and "protrusion". Inclusion criteria were limited to original articles and systematic reviews published in English, between the years 2000 and 2021, which pertained to the radiological landmarks to be identified during endoscopic skull base surgery. Full-text articles were retrieved and collated into a narrative review focused on a 12-item checklist the authors agreed upon. The mnemonic "O ROAD TO SELLA" was used to represent the checklist and include the following landmarks: Sphenoid Ostium, Sphenoid Rostrum, Onodi cells, Anatomic variations of the sphenoid sinus, Distance between the carotids, Tumor characteristics, Optic nerve dehiscence/protrusion, Septation/insertion of the sphenoid sinus, Entrance to the sellar floor, Lateral recess of the sphenoid sinus, cLinoid process pneumatization, and internal carotid Artery dehiscence/protrusion. The checklist is designed to be used by attending physicians, fellows, and residents and the authors intend to implement it into electronic medical records at the institution's medical center to monitor the outcomes of EEPS after implementation.

An artificial intelligence algorithm for the classification of sphenoid sinus pneumatisation on sinus computed tomography scans

BACKGROUND

Classifying sphenoid pneumatisation is an important but often overlooked task in reporting sinus CT scans. Artificial intelligence (AI) and one of its key methods, convolutional neural networks (CNNs), can create algorithms that can learn from data without being programmed with explicit rules and have shown utility in radiological image classification.

OBJECTIVE

To determine if a trained CNN can accurately classify sphenoid sinus pneumatisation on CT sinus imaging.

METHODS

Sagittal slices through the natural ostium of the sphenoid sinus were extracted from retrospectively collected bone-window CT scans of the paranasal sinuses for consecutive patients over 6 years. Two blinded Otolaryngology residents reviewed each image and classified the sphenoid sinus pneumatisation as either conchal, presellar or sellar. An AI algorithm was developed using the Microsoft Azure Custom Vision deep learning platform to classify the pattern of pneumatisation.

RESULTS

Seven hundred eighty images from 400 patients were used to train the algorithm, which was then tested on a further 118 images from 62 patients. The algorithm achieved an accuracy of 93.2% (95% confidence interval [CI] 87.1-97.0), 87.3% (95% CI 79.9-92.7) and 85.6% (95% CI 78.0-91.4) in correctly identifying conchal, presellar and sellar sphenoid pneumatisation, respectively. The overall weighted accuracy of the CNN was 85.9%.

CONCLUSION

The CNN described demonstrated a moderately accurate classification of sphenoid pneumatisation subtypes on CT scans. The use of CNN-based assistive tools may enable surgeons to achieve safer operative planning through routine automated reporting allowing greater resources to be directed towards the identification of pathology.

Morphometry and Intracranial Relations of the Sphenoid Sinus in Context to Endoscopic Transnasal Transsphenoidal Surgery

Introduction Due to the variable degree of pneumatization, the shape and size of the sphenoid sinus are irregular. An endoscopic intranasal transsphenoidal approach is made in sphenoid sinus pathologies, sphenoid sinusitis, and sellar and parasellar diseases. A diagnostic approach to the sphenoid sinus is also done to get a better MRI scan of the pituitary. The present study aims to describe the variant types of sphenoid sinus, morphometry, anatomy, and relations of sphenoid sinus, which will be helpful to surgeons during an endoscopic approach to the sphenoid sinus. Materials and methods We studied 76 cadaveric sphenoid sinuses that were exposed by taking a sagittal section of 38 formalin-fixed cadaveric heads. After examining the inter-sphenoidal septum, it was removed to observe the inside aspect of the sphenoid sinus. Different dimensions of the sinus were noted down. The bulges inside the sinus due to neurovascular structures in relation to the sinus were observed. Results  The most prominent type found was the sellar in 68.4% of cases preceded by the postsellar in 23.7% of cases. Presellar type of pneumatization was seen only in 7.9% of cases and the conchal type was absent. Intersphenoid septum was seen in 92,1% of cases, out of which 11.4% of septums were deficient on the posterior aspect. An internal carotid artery bulge in the sphenoid sinus was seen in 46% of cases. In 27.6% and 19.7% of sphenoid sinuses, bulging of the optic and vidian nerves, respectively, were seen. Some of these structures were dehiscent in the sphenoid sinus. Conclusions To get more space in the sphenoid sinus, the septa in the sinus are removed by surgeons, which may damage the walls of the sphenoid sinus. Knowledge of the relations of neurovascular structures with the sphenoid sinus will be helpful to surgeons during the transsphenoidal endoscopic approach to avoid any injury to these structures.

Association of accessory sphenoidal septum with protrusions of sphenoid sinus

PURPOSE

Accessory sphenoidal septum (ASS) is a septal variation that exists in addition to the primary septum of the sphenoid sinus and can be found in or near anatomically essential structures. This study aimed to investigate the relationships between protrusions of vital structures around the sphenoid sinus and the ASSs.

METHODS

This cross-sectional retrospective study is based on the analysis of CBCT scans of 314 patients in axial, coronal, and sagittal planes with 0.2-0.3 slice thicknesses. Optic nerve (ON), internal carotid artery (ICA), both ON and ICA, maxillary nerve (MN), vidian canal (VN) and ASSs were detected, and the relationship between protrusions of these vital anatomical structures and ASS was evaluated.

RESULTS

Statistically significant relationship was observed between the right Type 1 ON protrusion (p < 0.05) and left Type 1 ON protrusion (p = 0.001); left Type 3 ON protrusion (p < 0.05); right Type 4 ON protrusion (p < 0.05) and ASS. Statistically significant relationship was also observed between the right ICA protrusion and ASS (p < 0.05). The right Type 1 VN protrusion (p = 0.001); left Type 2 VN protrusion (p < 0.001); right and left Type 3 VN protrusions (p < 0.001) were found to be significantly associated with the ASS.

CONCLUSIONS

ASSs have significant associations with some protrusions, and they tend to cause potentially severe complications in endoscopic sinus surgery. This variability requires a comprehensive understanding of regional sphenoid sinus anatomy with detailed three-dimensional tomographic imaging.

Surgical anatomic findings of sphenoid sinus in 1009 Iranian patients with pituitary adenoma undergoing endoscopic transsphenoidal surgery

OBJECTIVE

The most common surgical technique for the management of pituitary adenomas is the endoscopic endonasal transsphenoidal approach (EEA). preoperative neuroimaging along with detecting surgical landmarks of the sphenoid sinus during surgery is important for making a successful operation.

METHOD

This study includes 1009 patients with pituitary adenomas who underwent EEA between 2013 and 2020. We evaluated the anatomical features of the sphenoid sinus through a panel of items obtained from imaging and intra-operative findings.

RESULTS

Our result includes 57.38% nonfunctional, 8.42% cushing, 12.39% prolactinoma, and 21.8% acromegaly patients who had undergone endoscopic endonasal transsphenoidal surgery. The mean age of the patients was 45 with a male to female ratio of 1.2:1. Sellar sphenoid type was the most common (91.8%) with only 12% symmetrical inter sphenoid septa, Internal carotid artery dehiscence was found in 1.7% of the cases. Apoplexy was present in 6.3% of patients, which was found more prevalent in nonfunctional adenomas (9.67%, Odds ratio: 4.85, 95% CI 2.24-11.79) and further investigation revealed a significant association between apoplexy and sphenoid mucosal edema and hemorrhage (Odds ratio: 43.0, 95% CI 22.50-84.26), and between apoplexy and cystic lesions (OR = 4.14, 95% CI 1.87-8.45, P-value < 0.0001). Acromegaly is associated with the increased number of lateral recces (Odds ratio: 11.41, 95% CI 7.54-17.52), septation of the sphenoid sinus (Marginal mean: 3.92, 95% CI 3.69-4.14), edematous sinonasal mucosa (Odds ratio: 6.7; 95% CI 4.46-10.08), and higher bony (OR: 4.81, 95% CI 2.60-8.97, P-value < 0.001) and cavernous (OR: 1.7, 95% CI 1.13-2.46, P-value < 0.01) invasion.

CONCLUSION

The present study provides anatomical data about the sphenoid sinus and its adjacent vital structures with adenomal specific changes that are necessary to prevent complications during endoscopic advanced transsphenoidal surgery.

Development of the Sphenoid Sinus in Japanese Children: A Retrospective Longitudinal Study Using Three-Dimensional Computed Tomography

Background: The sphenoid sinus (SS) is located close to vital structures, such as the pituitary gland, and it has significant clinical relevance. This study aimed to clarify the growth pattern of the SS in Japanese children using three-dimensional computed tomography (CT). Methods: Seventy-eight participants with congenital, acquired, or external auditory canal cholesteatoma were recruited and underwent CT more than twice during their treatment. Using the volume-rendered images, the size and volume of the SS were measured. Furthermore, on the scout image, the morphological measurements of the cranial base were determined. Results: The size and volume of the SS increased with age, and peaked at the mean age of 15 years. For males, the volume of the SS was smaller than that of females aged <5 years. The growth rate of the SS was significantly higher in males than in females. The maximum growth rate was detected at the age of 12 years for males and 10 years for females. For females, the increase in the length of the anterior cranial base ceased at approximately 10 years of age and remained constant thereafter. In contrast, for males, the length of the anterior cranial base increased gradually until 15 years of age. Conclusions: Considering the similarity of the periods between the adolescent growth spurt and the maximum growth rate of the SS, changes in the size of the SS may be used as an indicator of the physical growth spurt.

Racial, Ethnic, and Gender Variations in Sinonasal Anatomy

BACKGROUND

Complications during endoscopic sinus surgery often result from unfavorable anatomy. The prevalence rates of such anatomic findings vary tremendously in the literature, in part due to the small, homogenous populations previously studied.

OBJECTIVE

To characterize the prevalence of sinonasal anatomic variants among ethnic groups and genders seen at an academic medical center.

METHODS

This is a retrospective cross-sectional study of adult subjects who underwent CT imaging of the sinuses from January 2019 to November 2020 at a tertiary academic setting. CT scans were analyzed systematically by 3 trained study personnel for the presence of critical sinus anatomic variants that endoscopic sinus surgeons typically evaluate for preoperatively. Chi-squared tests and analyses of variance were conducted to detect differences in the prevalence of structural findings between genders and races/ethnicities.

RESULTS

A total of 489 subjects (57% female) were included: 44 Asian, 14 Black/African American, 101 Hispanic/Latino, 203 White, 127 Other. The prevalence of the following anatomical variants differed by race/ethnicity: Haller cells, Type 3 optic nerve, Onodi cells, maxillary septations, sphenoid lateral recess, anterior clinoid process pneumatization, and carotid artery dehiscence. Asian subjects had higher rates of Haller cells (48% vs 16%, P < .001) and Type 3 optic nerve (18% vs 4%, P = .022) compared to Hispanic subjects, as well as a higher prevalence of Onodi cells (39% vs 17%, P = .003) compared to White subjects. Males had a higher prevalence of mesenteric anterior ethmoid arteries (62% vs 45%, P < .001) and dehiscent carotid arteries (30% vs 21%, P = .024).

CONCLUSION

Certain sinonasal anatomic variants, which have direct implications for complications during endoscopic sinus surgery, were found to be significantly more prevalent in some demographic groups. Surgeons should be aware of these differences in their review of preoperative imaging for safe surgical planning.

Risky anatomical variations of sphenoid sinus and surrounding structures in endoscopic sinus surgery

Purpose

This study aimed to examine the relationship between the sphenoid sinus (SS) and surrounding vital structures such as the internal carotid artery (ICA) and optic nerve canal (ONC) as well as the types of attachment of the sphenoidal septa onto these structures.

Methods

In total, 230 computed tomography (CT) scans were reviewed to study the type of sphenoid sinus pneumatization (SSP), the protrusion and dehiscence of the ICA and ONC, the relationship between the sphenoidal septa and surrounding vital structures as well as pterygoid recess pneumatization (PRP).

Results

The most common SSP was sellar type (58.7%). The rates of protrusion and dehiscence of the ICA were 26.3 and 0.4%, and for the ONC, they were 13 and 1.5%, respectively. The ICA and ONC were most protruded and dehiscent in more extensive SSP. In 21.6% of patients, the intersphenoidal septa (IS) were attached to the wall of the ICA and in 8.6% they were attached to the wall of the ONC. The attachment of IS to the ICA correlated statistically significantly (p < 0.0001) with protrusion of the ICA. Accessory septa were detected in 30.4% of cases with various sites of attachment.

Conclusion

To reduce the risk of injury and complications during endoscopic sinus surgery (ESS), surgeons should consider using CT to identify possible bulging and dehiscence of the ICA/ONC and their relationship to the extent of SSP and also to establish the presence of deviation of the sphenoid septum, and the presence of accessory septa.

Relationships of sphenoid sinus pneumatization with internal carotid artery characteristics

Objective

We explored the clinical significances of the relationships among sphenoid sinus aeration, intersphenoid sinus septum (ISS), and internal carotid artery (ICA).

Methods

We retrospectively reviewed the preoperative paranasal sinus computed tomography scans and the medical charts of 490 patients who were treated by the endoscopic endonasal transsphenoidal approach. We analyzed sphenoid sinus pneumatization, number of ISS, and positional relationships between the ICA and ISS (including ICA prominence and the thickness of surrounding bone).

Results

ISS were often present in the ICAs of patients with presellar pneumatization (36.2%; p = 0.042). Sphenoid sinus pneumatization status significantly differed according to number of ISS (p < 0.001), ICA prominence (p < 0.001), ISS insertion into the ICA (p = 0.042), and distance from ISS to ICA (p = 0.004). When sphenoid sinus aeration was poor, the ICA was not prominent, and the ISS were attached to or lay close to the paraclival ICA.

Conclusions

Patients with presellar pneumatization exhibited less prominent ICAs, and more ISS attached to or near the paraclival ICA, than did other patients. Therefore, particular caution is required when using the endoscopic endonasal transsphenoidal approach to treat patients with poor sphenoid sinus aeration.

Pediatric Paranasal Sinuses- Development, Growth, Pathology & Functional Endoscopic Sinus Surgery

The paranasal sinuses (maxillary, frontal, ethmoid, and sphenoid sinuses) are complex anatomical structures. The development and growth of these have been investigated utilizing a number of different methods ranging from cadaveric analysis to modern cross sectional imaging with 3D modeling. An understanding of normal pediatric paranasal sinus embryology and development enables us to better determine when pathology may be affecting the normal developmental process. Cystic fibrosis, chronic sinusitis, deviated nasal septum and cleft lip and palate are some of the conditions which have been shown to effect paranasal sinus development to varying degrees. Functional endoscopic sinus surgery (FESS) is becoming increasingly common and an understanding of sinus anatomy together with when periods of rapid growth occur during childhood is important clinically. Although concerns have been raised regarding the impact of FESS on facial growth, there is limited evidence of this in regards to either changes in anthropomorphic measurements or clinical assessments of symmetry post operatively.

Bilateral Visual Loss Caused by Pneumosinus Dilatans: Idiopathic Cases are not Always Reversible

Purpose

To report a rare case of primary pneumosinus dilatans (PSD) and to specify the cardinal imaging findings associated with this condition.

Methods

A 20-year-old patient presented with bilateral profound visual loss as a result of primary PSD. A detailed review of clinical findings and presumed pathophysiological basis of vision loss was performed.

Results

Other than undiagnosed primary hypothyroidism, no other abnormalities were found. With the diagnosis of PSD, the patient underwent optic nerve decompression through transnasal sphenoidotomy. However, after nine months of follow-up, no improvement in the patient's vision was attained.

Conclusion

Unlike previous reports of favorable visual results after sphenoidotomy and bilateral decompression of the optic nerves, vision recovery was not achieved in this case.

Assessment of variations in sphenoid sinus pneumatization in Indian population: A multidetector computed tomography study

Background and Purpose:

The purpose of our study was to assess the prevalence of variations in the extent of sphenoid pneumatization in the Indian population and compare with existing literature.

Materials and Methods:

This retrospective study included 500 patients who underwent CT of the paranasal sinuses. The multiplanar reformations of paranasal sinus were assessed for the type of pneumatization of the sphenoid sinus and type of clival, lateral recess, lesser wing, and anterior recess extensions.

Results:

The conchal, presellar, incomplete sellar, and complete sellar types comprised 0%, 1.2%, 22.2%, and 76.6% of patients. The extensions of pneumatization subtypes in the study population were clival in 76.6% subjects; lateral recess, lesser wing, and anterior recess in 59.7%, 20.4%, and 20.4% of sinuses, respectively. The pure forms were seen in 25.4% and combined forms in 61% of sinuses. The presellar type (1.2%) was less common and sellar type (98.8%) being common in our population compared to the Caucasian and East Asian population. The sphenoid sinuses were extensively pneumatized in our population compared to the Chinese and Caucasian population, the prevalence being 76.6%, 68%, and 44.5% for clival; 59.7%, 46%, and 28.3% for lateral recess; 20.4%, 32%, and 12% for lesser wing extension, respectively. The pure forms were relatively less common and combined forms being more common compared to the Chinese and Caucasian population in our study.

Conclusion:

The extent of pneumatization of the sphenoid sinus has clinical and surgical implications in sellar and central skull base lesions, and variability in different populations confirms that ethnicity influences the differences in prevalence.

Morphometric characteristics of the sphenoid sinus and potential influencing factors: a retrospective assessment using cone beam computed tomography (CBCT)

The present study aimed to evaluate the morphological characteristics of the sphenoid sinus (SS), and the impact of potential influencing factors on the morphometric features using CBCT imaging. CBCT scans of 148 patients, aged between 15 and 85 (32.88 ± 15.33) years were retrospectively evaluated. DICOM files from the CBCT scans were imported into semi-automatic software and the SS of each patient was assessed for the morphological characteristics including configuration, symmetry, extension, shape, septation, volume, and maximum diameter. Furthermore, potential influencing factors such as age, gender, side, and sinus condition were analysed. A significant association was observed between sinus extension and age. Septation was also found to be significantly associated with age, gender and sinus condition. Besides, sinus volume was significantly associated with gender and sinus condition. No significant influence of shape and side on the morphometric features was noticed. The average volume and diameter of the SS were 6576.92 ± 3748.12 mm³ and 30.48 ± 9.28 mm, respectively. In conclusion, the present findings indicate that age, gender and sinus condition have a significant impact on the morphometric characteristics of the SS. Mature sinuses exhibit a post-sellar extension pattern until middle age. In addition, males, and sinuses with healthy sinus condition have larger volumes compared to females and pathological sinuses.

The pneumatization of the sphenoid sinus, its variations and relations with surrounding neurovascular anatomic structures: A computerized tomography study

INTRODUCTION AND OBJECTIVES

The wide range of variability of SS pneumatization and relation with surrounding structures can result in serious complications; seeing that, the assessment of regional anatomy is essential for both surgeons and radiologists. We mainly aim to reveal the possible correlation between the SS pneumatization types and protrusion/dehiscence of the adjacent neurovascular structures in a larger population by using computerized tomography (CT) images.

METHODS

The type of SS pneumatization (I-IV), pneumatization of anterior clinoid process (ACP), greater wing of sphenoid (GWS), and pterygoid process (PP) was evaluated. Protrusion and dehiscence of ICA, ON, MN, and VN was noted.

RESULTS

1003 patients were included into the study. ICA, ON, and MN protrusions were not seen in patients with the type I or II SS on both sides. These protrusions were most frequently seen along with the type IV SS on both sides (p < 0.05). ICA, ON, MN, and VN dehiscence was not found in any patients with the type I SS. The rate of ICA protrusion increased with presence of GWS and PP; ICA dehiscence was found to be positively correlated with ACP, GWS, and PP pneumatization.

CONCLUSIONS

Variations, either amount or the extent, of the pneumatization of the SS are related with the presence of protrusion/dehiscence of ICA, ON, MN and VN. Knowing and reporting these relations can decrease the rate of complications during skull base surgery.

Sphenoid Bone Pneumatisation on Lateral Cephalograms of Patients With Neurofibromatosis Type 1

BACKGROUND/AIM

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary disease that causes tumors and many developmental disorders, e.g., cranial dysplasia. The purpose of this retrospective study was to analyse the pneumatisation of the sphenoid bone in NF1.

PATIENTS AND METHODS

The anonymised lateral cephalograms of 166 NF1 patients and 166 age- and sex-matched controls were examined for anterior-posterior sphenoid pneumatisation. The patient group analysis considered whether the patients had been affected by a facial plexiform neurofibroma (FPNF).

RESULTS

Sphenoid pneumatisation was significantly lower in NF1 patients than in controls [odds ratio (OR)=0.184; 95%CI=0.11-0.32; p<0.001]. A FPNF statistically significantly reduced sinus formation in patients (OR=0.38; p=0.002).

CONCLUSION

The condition 'NF1' has an effect on sphenoid pneumatisation. The findings are relevant for planning surgical procedures in this region and confirm current concepts to evaluate NF1 as a histogenesis control gene. The examination technique and basis of calculation presented here are easy-to-use and low-irradiation exposure instruments for screening for differences in sphenoid bone pneumatisation in defined populations.

Paranasal sinus development and implications for imaging

Because the paranasal sinuses continue to develop throughout childhood, radiologists encounter significant anatomical variation when confronted with pediatric imaging studies. Knowledge of the stages of sinus growth is vital to differentiate normal development from abnormally large, hypoplastic or malformed sinuses. Understanding how the paranasal sinuses develop and their expected appearance at different patient ages is important for accurate interpretation of diagnostic imaging. To that end, we provide a brief review of paranasal sinus anatomy and discuss the mechanisms by which each paranasal sinus develops, as well as the implications for imaging. We also provide a practical guide for assessing normal paranasal sinuses in children based on the relationship of the sinuses to anatomical landmarks at various stages of development in order to help pediatric radiologists provide accurate interpretation of diagnostic imaging.

Anatomographic Variants of Sphenoid Sinus in Ethiopian Population

Neurosurgeons often neglect the sphenoid sinus due to its deep location and difficulties in accessing during surgical interventions. Disease of the sphenoid sinus is difficult to diagnose since its presenting symptoms are difficult to recognize. Moreover, compared with other paranasal sinuses, the sphenoid sinus is considered the most variable air sinus in terms of its degree of pneumatization, number and position of inter-sinus septa, and its relationship with the surrounding anatomical structures. Anatomical variations of the sphenoid sinus are significant from a neurosurgical point of view. Understanding of these variations and its relationships with surrounding structures such as the internal carotid artery, optic nerve, and pituitary gland are clinically relevant to minimize injuries associated with surgical procedures that involve sphenoid sinus. We implemented principles of imaging using computed tomography to elucidate any anatomical variations of the sphenoid sinus in the Ethiopian population. We conducted a prospective study in 200 patients with ages 18-79, who underwent scans of the sphenoid sinus at the Tikur Anbessa Referral Teaching Hospital in 2017-2018. Our findings revealed an incidence of anatomographical variations in terms of pneumatization that varied between 2-50%. These variants include 2% conchal, 25.5% presellar, 50% sellar, and 22.5% postsellar pneumatization. We also demonstrated anatomographic variants in terms of septation, 77.5% single complete septa, 11.5% single incomplete, 10% double septa, and 1% absence of septa. In summary, the sellar pneumatization was found to be the most clinically relevant anatomographic variant among Ethiopians participating in the study, of which 90% were tomographically single septated. These variants must be taken into consideration during trans-sphenoidal surgery and knowledge of the variations has clinical implication in minimizing injuries during invasive surgical procedures involving the sphenoid sinus.

Morphometric Alterations of the Sphenoid Ostium and other Landmarks in Acromegaly: Anatomical Considerations and Implications in Endoscopic Pituitary Surgery

Background

The sphenoid ostium (SO) is an important landmark for the endoscopic surgeon. Changes in size and position of the SO and variations in other skull base landmarks in acromegalics have not been adequately evaluated.

Aims

The authors evaluated the morphometry and location of the SO and other landmarks in acromegaly and compared these findings with those in nonfunctioning pituitary adenomas (NFPAs).

Methods

In this retrospective case-control study, the dimensions and location of the SO and other skull base landmarks were radiologically evaluated in 18 patients with growth hormone (GH)-secreting adenomas. These findings were analyzed in relation to preoperative GH levels and compared with 18 age- and sex-matched controls with NFPAs.

Results

The dimensions of the SO were significantly larger in the GH-adenoma group (P < 0.05). The SO was further from the midline (P = 0.04) and closer to the sphenopalatine foramen (SPF) (P = 0.02) in the GH-adenoma group, and this finding correlated with increasing preoperative GH levels. Acromegalics demonstrated larger intracavernous carotid diameters (P = 0.05) and smaller intercarotid distances than the patients with NFPAs (P = 0.02).

Conclusion

The SO is larger and located higher up in the sphenoid face and closer to the SPF in patients with GH adenomas. Increasing GH levels in these patients correlate with the upward and lateral displacement of the SO. These patients demonstrate larger intracavernous carotid diameters and smaller intercarotid distances than patients with NFPAs. These morphological alterations are of particular relevance to the pituitary surgeon.

Prevalence of accessory septations of sphenoid sinus in pediatric population: Applications to endoscopic sinus surgery

Sphenoid sinus accessory septations and their possible insertion on internal carotid artery (ICA) may represent a risk for endoscopic sinus surgical procedures. However, scarce data on this variant for children are available so far. This retrospective study included 220 maxillofacial CT-scans equally divided among males (13.4 ± 2.1 years) and females (13.9 ± 2.2 years). On each CT-scan, prevalence of accessory septations, number of septations in sphenoid sinuses, and their possible insertion onto ICA bone walls were recorded. Significant differences in protrusion and insertion of septations onto the ICA bone walls according to sex were assessed through Chi-square test (p < .05). Possible correlations between the prevalence of accessory septations, ICA insertion, and number of accessory septations and age were assessed by means of Pearson's regression (p < .05). On average, 66% of males and 71% of females had at least one accessory septation, without significant differences according to sex or age (p > .05): septal insertion on ICA was found in 13% of subjects, without any significant difference for sex or age (p > .05). The number of septations was significantly increased with age (p < .05). The present study showed that the prevalence of accessory septations and insertion onto the ICA are independent of age and these results are similar to those reported in adults. Results will be useful for the management of endoscopic sinus surgery.

Preoperative Computed Tomography Imaging of the Sphenoid Sinus: Striving Towards Safe Transsphenoidal Surgery

Introduction  Preoperative high-resolution computed tomography (HRCT) is essential in patients undergoing transsphenoidal surgery to identify potential high-risk anatomic variations. There is no consensus in the literature, as to which grading system to use to describe these variants, leading to inconsistent terminology between studies. In addition, substantial variability exists in the reported incidence of anatomic variants. In this study, we performed an institutional imaging analysis and literature review with the objective of consolidating and clearly defining these sphenoid sinus anatomical variations. In addition, we highlighted their surgical implications and propose a checklist for a systematic assessment of the sphenoid sinus on preoperative CT. Methods  Review of the literature and retrospective analysis assessing several imaging parameters in 81 patients who underwent preoperative HRCT imaging for endoscopic transsphenoidal tumor resection from January 2008 through July 2015 at Rush University Medical Center. Results  The most common sphenoid pneumatization patterns were sellar (45%) and postsellar (49%) types. Anterior clinoid process (ACP) pneumatization was seen in 17% of patients with high concordance of ipsilateral optic nerve (ON) protrusion. ON protrusion and dehiscence was present in 17 and 6% of patients, respectively. Internal carotid artery (ICA) protrusion and dehiscence was present in 30 and 5% of patients, respectively. Dehiscence rates from local bone invasion overlying the ICA and ON occurred in 17 and 4% of cases, respectively. Conclusions  Our study highlights and reviews the key variants that have potential to impact surgical complications and outcomes in a heterogeneous patient population. The proposed preoperative CT checklist for patients, undergoing transsphenoidal surgery, consistently identifies these higher risk anatomical variants.

The impact of sphenoid sinus pneumatization type on the protrusion and dehiscence of the adjacent neurovascular structures: A prospective MDCT imaging study

RATIONALE AND OBJECTIVES

Sphenoid sinus (SS) pneumatization is greatly variable. Precise determination of the pattern of SS pneumatization and its relationship to the vital neurovascular structures will provide a more comprehensive understanding of the regional SS anatomy to avoid the risk of potentially serious neural and vascular injury. We aimed to study the relationships among SS pneumatization type, extent of pneumatization, and protrusion/dehiscence of adjacent neurovascular structures using the multi-detector computed tomography.

MATERIALS AND METHODS

One hundred seventy healthy patients were prospectively examined by multi-detector computed tomography of the head. The type of pneumatization of the SS was determined. The protrusion/dehiscence of the internal carotid artery, optic nerve, vidian nerve, and maxillary nerve into the SS cavity was evaluated. The relationships between the SS pneumatization type and the extent of protrusion/dehiscence of the examined variables were statistically analyzed.

RESULTS

We had 70 patients with no protrusion/dehiscence, 37 patients with unilateral protrusion/dehiscence, and 63 patients with bilateral protrusion/dehiscence. The presellar type was dominant (61.4%) in the group with no protrusion/dehiscence, the sellar type was dominant (56.8%) in the group with unilateral protrusion/dehiscence, and the postsellar type was dominant (55.6%) in the group with bilateral protrusion/dehiscence. The protrusion rates of the internal carotid artery, optic nerve, vidian nerve, and maxillary nerve in the postsellar type were 50.6%, 52.3%, 56.9%, and 54.1%, respectively (p< 0.001).

CONCLUSION

The prevalence of protrusion/dehiscence of the neurovascular structures is significantly related to the type of SS and increases as the degree of SS pneumatization increases.

The Whole Lateral Type of the Sphenoethmoidal Cell and Its Relevance to Endoscopic Sinus Surgery

BACKGROUND

The sphenoethmoidal cell and the sphenoid sinus (SS) show great similarity in endoscopy and imaging. Hence, it is important to accurately identify the sphenoethmoidal cell preoperatively to prevent injury of the nerve and artery during endoscopic surgery. The aim of the present study was to investigate a special type of sphenoethmoidal cell.

METHODS

A total of 365 inpatients whose paranasal sinus computed tomography (CT) was collected and reviewed from May 2018 to September 2019 were included. The anatomical imaging characteristics of the sphenoethmoidal cell were observed.

RESULTS

A special type of the sphenoethmoidal cell was found on 9 sides in 730 sides (1.3%), according to its extension to the SS. Unlike Onodi cell (49.6%) and Jinfeng cell (1.3%), this cell simultaneously extends toward the superolateral, lateral, and inferolateral regions of the SS and is simultaneously closely attached to the optic canal and the maxillary nerve. Presently, this cell is named as the whole lateral type of the sphenoethmoidal cell, and the SS is located at the medial or inferomedial of it.

CONCLUSIONS

When evaluating the paranasal sinus CT preoperatively, attention must be paid to the possibility of the whole lateral type of sphenoethmoidal cell appearing, not just Onodi cell, extending into the SS.

Relation between volume of sphenoid sinuses and protrusion of Vidian nerve: possible applications to Vidian neurectomy

PURPOSE

Vidian neurectomy is a surgical procedure applied to different pathological conditions, including chronic rhinitis and sphenopalatine neuralgia. The choice of the correct surgical approach depends upon the possible protrusion of Vidian nerve into the sphenoid sinuses. The present study analyzes the possible relationship between protrusion of Vidian nerve and volume of sphenoid sinuses.

METHODS

In total, 320 maxillofacial CT-scans were retrospectively assessed. Subjects equally divided among males and females (age range 18-94 years) were divided into three groups according to the profile of Vidian nerve protrusion: type 1: Vidian nerve inside the sphenoid corpus; type 2: partially protruding into the sphenoid sinus; and type 3: entirely protruding into the sphenoid sinus through a stalk. Volume of sphenoid sinuses was extracted through the ITK-SNAP-free software and automatically calculated. Possible statistically significant differences in prevalence of the three types between males and females were assessed through Chi-squared test (p < 0.05). Differences in volume of sphenoid sinuses in subjects included within the three types were assessed through one-way ANOVA test (p < 0.05), separately for males and females.

RESULTS

Type 2 was the most prevalent (46.5%), followed by type 1 (38.8%) and type 3 (14.7%), without significant differences according to sex (p > 0.05). Volume significantly increased passing from type 1 to type 3 both in males (p < 0.01) and in females (p < 0.01).

CONCLUSIONS

The results prove the existence of a strict relationship between sphenoid sinuses pneumatization and protrusion of the Vidian canal and give a contribution to the knowledge of this important anatomical variant in endoscopic surgery.

Morphometric Analysis of Sphenoid Sinus in Patients With Nasal Septum Deviation

This retrospective study aimed to assess the association of the volume and types of the sphenoid sinus with deviated nasal septum by analyzing multislice computed tomography images. A total of 93 patients with a deviated nasal septum and 70 healthy controls were included in the study. Patients with sinonasal morbidities other than deviation were excluded. Three-dimensionally reconstructed computed tomography images of the study participants were acquired. A total of 326 sphenoid sinus volumes from the patient and control groups were obtained and compared between the groups. Sphenoid sinus volumes and the angle of the deviation were measured for standardization and assessment of the severity. Deviated nasal septum was found on the right in 49.5% (n = 46) and on the left in 50.5% (n = 47) of the study participants. Deviation angles were in the range from 7.2° to 22.4° and the mean value was 13.2° ± 5.0°. The measured volumes were in the range from 1.8 cm to 9.6 cm with a mean of 4.8 ± 1.5 cm. In the control group, the median values for the sphenoid sinus volumes were 4.40 cm (0.80-8.90 cm) on the right and 4.20 cm (0.90-8.70 cm) on the left. In the study group, sphenoid sinus volumes were found to be statistically significantly different between those on the ipsilateral and contralateral side of the septal deviation. Sphenoid sinus volumes were significantly smaller on the same side with septal deviation compared with those on the contralateral side. There was no statistical relationship between the presence of septal deviation, age and gender, and the type of sphenoid sinus.

Relationship between sphenoid sinus volume and accessory septations: A 3D assessment of risky anatomical variants for endoscopic surgery

Sphenoid sinus accessory septations involve serious complications during their removal for the injury of the internal carotid artery (ICA) and the optic nerve (ON). The relationships of this anatomical variant with sphenoid size still remain unclear. In the present study, 260 patients (equally divided among sexes, aged between 18 and 92 years) were retrospectively assessed. Number of accessory septations and their relationship with ICA and ON were recorded. The 3D model of sphenoid sinuses was extracted. Pearson's coefficient was calculated to assess correlations between the volume of sphenoid sinuses and the number of septations (P < 0.05). Sex-related differences in prevalence of septations inserted onto ICA or ON were assessed through chi-square test (P < 0.05). Differences in volume between patients with and without ICA or ON septal insertions were assessed through Mann-Whitney test (P < 0.05). In most of the cases, two septations were found (24.6%), whereas only 21.9% of patients did not show any septum. ICA and ON septal insertions were found in 20.8% and 7.7% of cases, respectively. Number of septations significantly increased with sinus volume, independently from sex (P < 0.001). Moreover, volume was significantly higher in patients with ICA septal insertion (P < 0.001), whereas no difference was found between subjects with and without ON septal insertion (P > 0.05). The present study first proved that septations and probability of ICA insertion are related with sphenoid volume. On the other side, ON insertion does not depend upon sphenoid sinuses size. Anat Rec, 303:1300-1304, 2020. © 2019 American Association for Anatomy.

Posterior ethmoid cell expansion towards the inferolateral region of the sphenoid sinus: a computed tomography study

OBJECTIVE

The aim of this study was to investigate the anatomical imaging characteristics of posterior ethmoid cells (PEs) expanding towards the inferolateral region of the sphenoid sinus (SS).

METHODS

This study included a total of 278 inpatients (556 sides) whose paranasal sinus computed tomography (CT) scans were reviewed and collected from May 2018 to February 2019. The anatomical imaging characteristics of PEs expanding towards the inferolateral region of the SS were observed.

RESULTS

PEs expanding towards the inferolateral region of the SS formed an inferolateral spheno-ethmoid cell (ISEC). ISECs were observed on three sides (0.54%; 3/556) in three cases (1.08%; 3/278). All of the ISECs were present unilaterally on the right side of the SS. The ISECs originated from the most posterior ethmoid cell; they were first located at the medial aspect of the orbital apex, pneumatized continually backward to the inferomedial wall of the orbital apex, and then extended into the lateral region of the SS. The ISECs further extended laterally, inferiorly and posteriorly beyond the sphenoid body into the greater wing and/or pterygoid process.

CONCLUSION

An ISEC is a rare variation of ethmoid air cells. Preoperative recognition of ISECs is essential to achieve safe and effective endoscopic sinus surgery because of the important anatomical location.

Relationship between sphenoid sinus volume and protrusion of internal carotid artery and optic nerve: a 3D segmentation study on maxillofacial CT-scans

PURPOSE

Anatomy of sphenoid sinuses has acquired a growing importance with the diffusion of transsphenoidal surgical procedures. A common risk in these practices is the damage of internal carotid artery (ICA) and optic nerve (ON), which may protrude into the sphenoid air cavities. This study aims at analysing the relationships between sphenoid sinuses volume and protrusion of ICA and ON.

METHODS

260 head CT-scans were retrospectively analysed (equally divided among males and females, age range 20-92 years). Volume was segmented through ITK-SNAP software. In addition, the subjects were classified into four groups: no protrusion of any structure (group 1), protrusion of ICA (group 2), protrusion of ON (group 3), protrusion of both ICA and ON (group 4). Possible statistically significant differences in prevalence of the four groups according to gender were assessed through Chi-squared test (p < 0.05). Differences in volume between the four groups were assessed through one-way ANOVA test (p < 0.05), separately for males and females.

RESULTS

Group 1 was the most frequent (40.0%), followed by group 4 (27.7%) and group 2 (18.5%), without any difference according to gender. For what concerns volume, cases of ICA and concomitant ICA + ON protrusion had significantly larger sinuses, whereas isolated ON protrusion did not modify sinus volume.

CONCLUSIONS

Results show that protrusion of ICA is positively related with the volume of sphenoid sinuses, whereas the same relation was not verified for ON: surgeons should accurately consider possible ON protrusion in each case, as it may occur independently from sphenoid sinuses volume.

Rhinogenous optic neuritis with full recovery of vision - The role of endoscopic optic nerve decompression and a review of literature

BACKGROUND

Optic neuritis resulting from paranasal sinusitis is an infrequently described but clinically important and treatable entity. The role of optic nerve decompression has been well established in atraumatic optic neuropathies which are compressive in origin. However, its role in optic neuritis and other infective or inflammatory processes is lacking, and the role for early surgical intervention remains controversial.

CASE REPORT

In this case report, we describe a patient who presented with sudden onset of right vision loss secondary to optic neuritis from pansinusitis. He was treated with systemic antibiotics and steroids along with an urgent endoscopic sinus surgery with optic nerve decompression. Full restoration of his vision was recorded within 24 h of surgical decompression.

CONCLUSION

Optic neuritis secondary to paranasal sinusitis is a clinically important entity and timely diagnosis and decompression is key to vision restoration.

Neurovascular Surgical Keys Related to Sphenoid Window: Radiologic Study of Egyptian's Sphenoid

OBJECTIVES

The anatomic variations of the sphenoid sinus and its relation to the surrounding neurovascular structures are a subject of interest. The purpose of this study was to radiologically assess the frequency of protrusion/dehiscence of key neurovascular landmarks surrounding the Egyptians' sphenoid.

METHODS

This is a cross-sectional descriptive study of sinonasal computed tomography of the sphenoid sinus in 500 adult Egyptians, conducted at Mansoura University Hospitals; Egypt, over a period of 1 year. Two archives were used for collecting the data; the hard archive and the electronic archive. Variables of interest included the extent of sphenoid sinus pneumatization; intersphenoid septation pattern; protrusion/dehiscence of the internal carotid artery, optic nerve, maxillary nerve, and vidian nerve; and detection of the Onodi cell.

RESULTS

Population of this study included 265 women and 235 men. Their ages ranged from 18-68 years. The bilateral sellar-type pneumatization was shown as the most common pneumatization type (96.8%). Pneumatizations of the pterygoid process, anterior clinoid process, and greater wing of the sphenoid were identified in 9.3%, 8.9%, and 31.8% consequently. A single intersphenoid septum was detected in 85.2%, whereas multiple intersphenoid septums were noted in 11.6%. Protrusion of the internal carotid artery, optic nerve, vidian nerve, and maxillary nerve was recorded in 8.5%, 9.1%, 6.6%, and 3.4% consequently, while dehiscence was reported in 7.2%, 15%, 11.9%, and 4.2% consequently as well. Onodi cell was recognized in 18%.

CONCLUSIONS

This radiologic study highlights significant variations of surgically important anatomic structures related to the sphenoid sinus in Egyptians.

A bony defect of the sphenoid air sinus found in male cadaver: a case report

The sphenoid sinus one of the posterior group of sinus, considered one of the most difficult sinuses due to its deep location in the skull. The interest in the understanding of the anatomy of the sphenoid sinus increased markedly during the last decades due to the development of endoscopic transsphenoidal approaches to the intracranial structures. The important anatomical relations of the sphenoid sinus make it one of the difficult and challenging structures for the surgeons. In this case report, we present one of the anatomical variations that was found during cadaveric dissection of the head. In this case we found abnormal bony defect in the lateral wall of the sinus, the defect closed just by the lining mucosa of the sinus and the dura from its intracranial side. A point may be of clinical importance to the related nearby structures.

Calculation of an Optic Nerve Injury Risk Profile Before Sphenoid Sinus Surgery

OBJECTIVES

Our objective was to analyze variations in the optic nerve (ON) course and surrounding structures in an effort to construct an optic nerve injury risk profile before endoscopic intranasal sphenoidal, or endoscopic endonasal transphenoidal, skull-base surgery, and eventually to construct and formulate a common classification by combining the known classes. The authors used computed tomography (CT) toward this end.

METHODS

The authors retrospectively reviewed 200 consecutive CT scans (400 sides) of the paranasal sinuses. The pneumatization of the anterior clinoid process, the relationships of the ONs to the sphenoidal sinuses, and ON dehiscence were evaluated. The authors then created a formula by which risk profiles can be constructed for patients for whom sphenoid or parasellar surgery is planned.

RESULTS

Pneumatization of the anterior clinoid process was evident in 28.25%. Dehiscence of the bony wall of the ON was evident in 9.5%. The ON course lay adjacent to the sphenoidal sinus, causing sinus wall indentation, in 23%. Cumulative optic nerve injury risk scoring showed that, radiologically, surgery on 8.5% and 1.5% of sphenoid sinuses described here carried severe or critical risk of ON injury, respectively.

CONCLUSIONS

Head-and-neck surgeons and neurosurgeons should be aware of variations in ON course. The authors composed an optic nerve injury risk classification category based on the sum of individual weights of each of these classes. Reductions in ON injuries require careful evaluation of potential variant anatomies. Preoperative CT scans must be meticulously reviewed to avoid ON injury.

An Analysis of Anatomic Variations of the Sphenoid Sinus and Its Relationship to the Internal Carotid Artery

Introduction  The sphenoid sinus (SS) has a high variability; its anatomical relations and variations must be well understood prior to the expanded endoscopic surgery (EES) at the skull base via the endonasal transsphenoidal approach. A feared complication is injury to the internal carotid artery (ICA).

Objective  To evaluate the anatomic variations of the SS and its relationship to the ICA using computed tomography (CT).

Methods  Cross-sectional retrospective study. Analysis of 90 patients' CT scans on axial, coronal and sagittal planes with 1 mm slices, evaluating lateral and posterior extensions of pneumatization of the SS, deviation of the sphenoid septum, presence of septations and their relationship to the parasellar and paraclival segments of the internal carotid artery (psICA and pcICA, respectively).

Results  The association between the protrusions of the psICA and the pcICA was statistically significant ( p  < 0.001), as was the association between the lateral extension of pneumatization of the SS and the protrusion of the psICA ( p  = 0.014). The presence of the posterior extension of pneumatization of the SS and protrusion of the pcICA occurred in 46% of the cases. Deviation of the sphenoid septum in the direction of the pcICA was present in 14% and dehiscence of the pcICA was seen in 3.6% of the cases.

Conclusion  Using the CT scan to recognize the type of extensions of pneumatization of the SS, the deviation of the sphenoid septum, and the presence of septations is beneficial to identify accurately the ICA and to reduce the risk of injury to it.

Radiological sinonasal anatomy. Exploring the Saudi population

OBJECTIVES

To assess the prevalence of common radiological variants of sinonasal anatomy among Saudi population and compare it with the reported prevalence of these variants in other ethnic and population groups. 

METHODS

This is a retrospective cross-sectional study of 121 computerized tomography scans of the nose and paranasal sinuses of patients presented with sinonasal symptoms to the Department of Otorhinolarngology, King Fahad Hospital of the University, Khobar, Saudi Arabia, between January 2014 and May 2014. 

RESULTS

Scans of 121 patients fulfilled inclusion criteria were reviewed. Concha bullosa was found in 55.4%, Haller cell in 39.7%, and Onodi cell  in 28.9%. Dehiscence of the internal carotid artery was found in 1.65%. Type-1 and type-2 optic nerve were the prevalent types. Type-II Keros classification of the depth of olfactory fossa was the most common among the sample (52.9%). Frontal cells were found in 79.3%; type I was the most common.  

CONCLUSIONS

There is a difference in the prevalence of some radiological variants of the sinonasal anatomy between Saudi population and other study groups. Surgeon must pay special attention in the preoperative assessment of patients with sinonasal pathology to avoid undesirable complications.

Sphenoid sinus barotrauma in diving: case series and review of the literature

About 50% of scuba divers have suffered from barotrauma of the ears and about one-third from barotrauma of paranasal sinuses. The sphenoid sinuses are rarely involved. Vital structures, as internal carotid artery and optic nerve, adjoin the sphenoid sinus. Thus, barotrauma could lead to serious neurologic disorders, including blindness. After searching the literature (Medline) and other sources (Internet), we present some cases of sphenoid sinus barotrauma, because these injuries may be underreported and misdiagnosed due to the lack of awareness and knowledge. Therefore, information is provided, e.g. on anatomical and pathophysiological features. Divers and physicians should have in mind that occasional headache during or after diving sometimes signals serious neurological disorders like vision loss. We show that injuries can develop from both negative and positive pressures in the sinuses. Because visual recovery depends on prompt diagnosis and proper therapy, physicians like otolaryngologists, ophthalmologists and neurologists need to closely collaborate.

Onodi cell mucocele: Case report and review of the literature

Onodi cell mucoceles are rare entities that can cause devastating ocular complications if not treated promptly. Delays in the diagnosis are possible because of the wide range of differential diagnoses of unilateral retrobulbar optic neuropathy. We describe a new case of Onodi cell mucocele in a 39-year-old woman, and we present a comprehensive review of the literature on this entity. To the best of our knowledge, no review of Onodi cell mucoceles has been previously published. Our review found that 69% of patients with an Onodi cell mucocele experienced an improvement in vision after surgical decompression. The vast majority of these patients underwent endoscopic decompression; the timing of surgical decompression did not appear to affect outcomes in terms of vision. Onodi cell mucocele requires a high degree of clinical suspicion for diagnosis and a multidisciplinary approach to management that involves primary care physicians, ophthalmologists, and otolaryngologists. Early surgical treatment via an endoscopic approach is recommended for most patients, regardless of the duration of their ophthalmologic signs and symptoms.

Detailed Anatomical Analysis of the Sphenoid Sinus and Sphenoid Sinus Ostium by Cone-Beam Computed Tomography

The aim of this study is the evaluation of the anatomical structures of sphenoid sinus ostium used as a reference point for transsphenoidal surgery by cone beam computed tomography. The authors' study was performed using the cone-beam computed tomography images of 16 to 82-year old 200 (112 female, 88 male) patients (Newton 5G, Verona, Italy). Septum deviation of sphenoid sinus and the distance between 2 ostia were evaluated by coronal and axial sections, respectively. Pneumatization degree of sphenoid sinus, diameter of sphenoid sinus ostium, and distance lower edge of superior turbinate to sphenoid sinus ostium were measured by using sagittal sections. The sellar type was the most common pneumatization type of sphenoid sinus in authors' study. While the C-type septum deviation was observed as the most common, T-type deviation was the least type. Sphenoid sinus ostium was bilaterally in 71.5% of individuals, and it was not found in 10% of individuals included in the study. A significant decrease was determined in diameter of the left sphenoid sinus ostium with aging. The distances between 2 sphenoid sinus ostia were 7.30 ± 2.77 mm for women and 6.09 ± 2.58 mm for men, respectively. No statistical differences were found in women and men in terms of distances between the lower edge of the right and left superior turbinate and sphenoid sinus ostium on their sides. Consequently, making detailed preoperative radiological evaluation of anatomic variations of sphenoid sinus and sphenoid sinus ostium is important in terms of guiding the surgeon in the process of a successful transsphenoidal surgery.

Anatomical variants of sphenoid sinuses pneumatisation: a CT scan study on a Northern Italian population

Sphenoid bone may be affected by different variants of pneumatisation, which have a relevant importance from a clinical and surgical point of view. The description of such variants in different populations may give useful information. However, few articles describe the variability of sphenoid pneumatised structures and none of them focuses on Northern Italian population. Variants of pneumatisation of sphenoid bone were described in a sample of 300 Northern Italian patients who underwent a CT scan. More than fifty-seven percent of patients showed a form of anatomical variant: the most common form was the pneumatised pterygoid processes (39.6%), followed by dorsum sellae (32.9%) and clinoid processes (20.3%), without statistically significant differences between males and females (p > 0.01). In 26.3% of patients, a combined pneumatisation of these three structures was observed, being the combination pterygoid processes-dorsum sellae the most frequent (11.3%). In 9.3%, all the three sphenoid structures were affected. This article is the first description of the prevalence of different variants of pneumatisation in a Northern Italian population: the occurrence of such forms has to be acknowledged for their possible clinical and surgical consequences.

Protrusion of the Infraorbital Nerve into the Maxillary Sinus on CT: Prevalence, Proposed Grading Method, and Suggested Clinical Implications

BACKGROUND AND PURPOSE

The infraorbital nerve arises from the maxillary branch of the trigeminal nerve and normally traverses the orbital floor in the infraorbital canal. Sometimes, however, the infraorbital canal protrudes into the maxillary sinus separate from the orbital floor. We systematically studied the prevalence of this variant.

MATERIALS AND METHODS

We performed a retrospective review of 500 consecutive sinus CTs performed at our outpatient centers. The infraorbital nerve protruded into the maxillary sinus if the entire wall of the infraorbital canal was separate from the walls of the sinus. We recorded the length of the bony septum that attached the infraorbital canal to the wall of the maxillary sinus and noted whether the protrusion was bilateral. We also measured the distance from the inferior orbital rim where the infraorbital canal begins to protrude into the sinus.

RESULTS

There was a prevalence of 10.8% for infraorbital canal protrusion into the maxillary sinus and 5.6% for bilateral protrusion. The median length of the bony septum attaching the infraorbital canal to a maxillary sinus wall, which was invariably present, was 4 mm. The median distance at which the infraorbital nerve began to protrude into the sinus was 11 mm posterior to the inferior orbital rim.

CONCLUSIONS

Although this condition has been reported in only 3 patients previously, infraorbital canal protrusion into the maxillary sinus was present in >10% of our cohort. Identification of this variant on CT could help a surgeon avoid patient injury.

Anatomical variants of surgically important landmarks in the sphenoid sinus: a radiologic study in Southeast Asian patients

PURPOSE

Failure of a surgeon to understand the local variations of the anatomical landmarks of the sphenoid sinus is a potential risk factor to cause damage to the optic nerve (ON) or internal carotid artery (ICA) that lies on the walls of the sphenoid sinus. The aim of this study was to identify the anatomical variants of the sphenoid sinus and its related surrounding structures among the Southeast Asian (SEA) population, based on computed tomography (CT) scans.

MATERIALS AND METHODOLOGY

This cross-sectional study analyzed 300 CT scans of the brain, paranasal sinuses (PNS), and head and neck (H&N) at a tertiary referral centre in Malaysia utilizing the Osirix software. The images were reconstructed into 1 mm cuts on bone window. Demographic details and scan findings were documented in a standardized data collection sheet.

RESULTS

The rates of ON dehiscence, ICA dehiscence and ICA protrusion in the SEA population were 7.0, 3.0 and 10.0 %, respectively. The rate of ON protrusion was 2.3 %. There was no statistically significant relationship (p > 0.05) noted on Chi-square test, between anterior clinoid process (ACP) pneumatization and ON protrusion. The rate of Onodi cells in our population was 14.3 %. The average vertical distance of the ostia from the roof of the posterior choanae was 1.42 cm (±0.32). The horizontal distance of the ostia from the anterior end of the superior turbinate was 1.58 cm (±0.41) and the oblique distance of the ostia from the anterior nasal spine was 5.35 cm (±0.48). Independent t tests showed that there is a statistically significant difference between the means of each of these parameters (p < 0.001) and their international averages.

CONCLUSION

The rate of ON protrusion is lower in the SEA population, whereas the rates of ON dehiscence, ICA dehiscence and ICA protrusion fall within the range of international averages. In our population, ACP pneumatization is not related to ON protrusion. The distance of the ostia from given landmarks was significantly shorter than in other studies.