Protrusion of the optic nerve into the ethmoid and sphenoid sinus: prospective study of 150 CT studies

Do Anatomical Variations of Sphenoid Sinus Influence Sella Exposure and Residual Disease in Pituitary Surgery? - A Study in an Indian Population

Introduction  Endoscopic transsphenoidal surgery (ETS) is the standard practice in pituitary surgeries. The sellar exposure becomes the main factor which determines the residual disease in ETS. Not many studies can be found in the literature on the influence of anatomical variations of the sphenoid on intraoperative sella exposure. Objective  The aim of the current study is to ascertain whether sphenoid sinus variations play a role in sellar exposure and residual tumor volume. Methods  This is a prospective study conducted in a south Indian tertiary care center between June 2020 to June 2022, with 21 study participants who were scheduled to have ETS. The relation of preoperative computed tomography (CT) and magnetic resonance imaging (MRI) parameters with the intraoperative area of sellar exposure and residual tumor volume was evaluated. Results  Sphenoid sinus dimensions, like presellar width (mean = 1.89 ± 0.51 cm), maximum width (mean = 2.94 ± 1.09 cm), presellar depth (mean = 1.14 ± 0.55 cm), suprasellar depth (mean = 1.08 ± 0.24 cm), infrasellar depth (mean = 2.36 ± 0.92 cm), presellar height (mean = 2.22 ± 0.47 cm), or the 9 internal carotid artery (ICA)-related measures, did not have any correlation with the mean intraoperative area of sellar exposure (0.57 ± 0.28 cm 2 ). Also, the adequacy of sellar exposure did not relate to the residual tumor. Preoperative tumor volume was found to be higher (20.2 [55.3-13.2] cm 3 ) in patients with residual tumor compared with those with no residual tumor (5.9 [6.8-5.2] cm 3 ). Tumor extension had a significant association with the residual tumor volume. Conclusion  According to the present study, anatomical variations of the sphenoid sinus do not influence the adequacy of sellar exposure. Further studies need to be undertaken concerning residual tumor volume as well as preoperative tumor volume and extension.

Type IV optic nerve and Onodi cell: is there a risk of injury during sphenoid sinus surgery?

Objective

This study aims to determine the prevalence and types of Onodi cells through computed tomography and investigate the relationship between Onodi cell and the surrounding structures, paying particular attention to the risky proximity to the optic nerve canal.

Methods

In this study, 430 computed tomography scans of paranasal sinuses were analysed to establish the prevalence and different types of Onodi cells. Furthermore, the relationship between Onodi cell and different patterns of sphenoid sinus pneumatisation and surrounding structures were investigated. Special attention was paid to the relationship between Onodi cell and the optic nerve canal, particularly in cases when the optic nerve canal was bulging by more than 50% into the Onodi cell (Type IV).

Results

The Onodi cell was detected in 21.6% of cases, with the most common being Type I (48.5% right, 54.3% left). Type IV bulging of the optic nerve canal into the Onodi cell was observed in 47.1% of cases on the right side, 41.2% on the left side and bilateral in 11.7% of cases.

Conclusions

In our series, we observed a high prevalence of Type IV optic nerve bulging into the Onodi cell. For this reason, we suggest that clinicians should always try to identify it in a pre-operative setting with computed tomography to avoid catastrophic consequences during endoscopic sinus surgery approaching the sphenoid area.

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.

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.

Anatomical Study of Ethmoidal Foramina and Optic Canal in Endoscopic Trans-Nasal Approach to Anterior Skull Base

BACKGROUND

Surgery to anterior skull base is challenging since complex structures are involved. Injury of olfactory fila and optic nerve may result in postoperative complications. In our study, the authors aim to use computer topographic image to provide a comprehensive anatomical information of anterior skull base and set up a new classification of optic canal (OC) in ethmoid sinus by the degree of bony defect, so as to help surgeons in endoscopic transnasal approach to anterior skull base.

METHOD

Computer topographic angiography images of 112 individuals were reviewed, the measurement was performed on coronal, sagittal, and axis planes after the multiplanar reformation. Nostril and mid-sagittal lines were used to locate the anterior, middle, and posterior part of ethmoidal foramina and orbital opening of OC. Further, the authors classified OC in ethmoidal sinus into 4 types by the degree of the bony defect.

RESULT

Distance between nostril to anterior, middle, and posterior part of ethmoidal foramina and OC are 6.23 ± 0.21, 6.62 ± 0.26, 7.29 ± 0.25, and 7.76 ± 0.41 mm, respectively. Angle between line from nostril to ethmoidal foramina and horizontal plane are 47.50° ± 1.03°, 41.67° ± 1.33°, 37.20° ± 1.34°, respectively. For the 4 types of OC, the percentage is 15.6%, 11.6%, 31.3%, and 41.5%, respectively.

CONCLUSIONS

Our findings provide anatomical information of ethmoidal foramina and OC during endoscopic transnasal approach to anterior skull base, on the basis of some fixed anatomical landmarks. So as to enhance the surgical safety of this procedure and aid in the choice of the appropriate endoscopic equipment for the procedure.

Cone Beam Computed Tomography Analysis of Sphenoid Sinus Pneumatization and Relationship with Neurovascular Structures

Background

The sphenoid sinus is considered as the most variable pneumatized structure of the skull.

Purpose

The aim of the present study was to determine the prevalence of the Onodi cell as well as to evaluate the relationship between the sphenoid sinus type of pneumatization and the presence of surrounding neurovascular protrusion using cone beam computed tomography (CBCT).

Methods

The CBCT images of 500 patients/996 sides [203 males (40.6%) and 297 females (59.4%)] were analyzed in this study. The type of sphenoid sinus pneumatization, prevalence of internal carotid artery (ICA) and optic nerve (ON) protrusion and dehiscence, and also the frequency of Onodi cell were assessed.

Results

The percentages of the conchal, presellar, sellar, postsellar (a), and postsellar (b) types of pneumatization were 1%, 11.5%, 35.5%, 38.9%, and 13.1%, respectively. The more the sphenoid sinuses pneumatized, the greater the frequency of ON and ICA protrusion and dehiscence of their wall to the sinus. The prevalence of Onodi cell was 38.8%. A significant correlation was found between ON dehiscence and the presence of Onodi cells.

Conclusion

The present study demonstrated a significant relationship between the sinus type and frequency of neurovascular protrusions. Therefore, the sphenoid sinus extent of pneumatization might be useful in predicting the risk of iatrogenic damage to the surrounding structures.

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.

Is there a relationship between Onodi cell and optic canal?

OBJECTIVES

We investigated the relationship between Onodi cells and optic canal by paranasal sinus computed tomography (PNSCT).

METHODS

In this retrospective study, 508 PNSCT (265 males and 243 females) was examined. Onodi cell presence, pneumatization types, optic canal types; and also sphenoid sinusitis and anterior clinoid process pneumatization were evaluated.

RESULTS

The prevalence of Onodi cells was 21.2% of the patients. Onodi cells were observed 40.7% on the right side and 25.9% on the left side. In 33.4% of the patients, bilateral Onodi cells were present. Male/Female ratio was 24.5%/17.6%. Onodi cell types were detected as Type I > Type II > Type III bilaterally. There was a positive correlation between the right and left Onodi cell types (p < 0.05). Optic canal types were detected as Type IV > Type I > Type II > Type III. bilaterally. There was a positive correlation between right and left optic canal types. Onodi cell presence and ACP pneumatization were found as statistically significant (p < 0.05). In 65.5% of the patients, Onodi cells and ACP pneumatization were absent. ACP pneumatization was present in 35.4% of the cases. In nine cases, bilateral Onodi cells and ACP pneumatization were detected. Sphenoid sinusitis was detected in 11.4% of Type I and 13.8% of the Type II Onodi cells on the right side. On the left side, it was detected in 12.9% of the Type I and 19.0% of Type II Onodi cells.

CONCLUSION

Identification of Onodi cell is very important clinically because of its proximity to optic nerve canal. We concluded that type IV Onodi-optic canal relationship was the most common finding in our study. Onodi cell presence and their patterns of pneumatization must be evaluated on PNSCT preoperatively to avoid optic canal damage.

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.

The prevalence of the Onodi cell - Most suitable method of CT evaluation in its detection

BACKGROUND

The Onodi cell (sphenoethmoidal air cell) is an anatomic variant of the most posterior ethmoid cell that pneumatised superiorly and laterally to the sphenoid sinus, and is in close relation to the optic nerve. The proper identification of the Onodi cell is essential during a pre-operative computer tomography (CT) examination, as the presence of that ethmoid cell variant makes sphenoid sinus surgery more risky. The bulging of the optic nerve to the ethmoid cell wall is well visualized during endoscopic examination, but there are no clearly defined criteria for a potentially dangerous Onodi cell type in CT examinations.

OBJECTIVE

To determine the prevalence and types of Onodi cell in CT examination and find the most suitable CT scanning planes to identify it.

MATERIAL AND METHODS

Three plane (axial, coronal and sagittal) reconstructions of 196 paranasal sinuses were analyzed. The most posterior ethmoid cell was classified into four types, according to its position in relation to the sphenoid sinus and the optic nerve canal bulging into the lumen of the sphenoethmoid cell.

RESULTS

The Onodi cell was detected in 39.8% of cases, although in 55.6% of cases a direct contact between the most posterior ethmoid cell and the optic nerve was present. Bulging of the optic nerve canal was seen in 25% of cases. In two cases two posterior ethmoid cells were in direct contact with the optic nerve canal.

CONCLUSION

The prevalence of the Onodi cell was higher than previously reported. Pre-operative paranasal sinuses CT examination should be evaluated in all three planes (axial, coronal and sagittal) to avoid missing or over-detection of the Onodi cell. Axial and sagittal planes are preferable for the detection of the Onodi cell.

Optic Nerve Canal Relation to Posterior Paranasal Sinuses in Indian Ethnics: Review and Objective Classification

INTRODUCTION

Posterior paranasal sinuses consisting of posterior ethmoid and sphenoid sinuses show varying pneumatization and relationship to Optic Nerve Canal (ONC). Most commonly ONC is superolateral to sphenoid sinus, however varied protrusion of ONC into the sinuses may occur. Rarely it may pass completely through the sinus. Optic Nerve (ON) is covered by a thin bony layer or by periosteum and sinus mucosa without bone. Extensive pneumatization of sphenoid sinus and bony dehiscence predisposes to ON injury. The posterior ethmoid cell namely the Onodi cell is of great surgical importance when the ON is along its lateral wall and surrounds the nerve. These varied relations imply that a detailed knowledge of the intimate relationship of ONC with the posterior paranasal sinuses is necessary to avoid unintentional complications during the surgeries involving the ONC region.

AIM

To assess relationship of ONC to the posterior paranasal sinuses in Indian Ethnic study group.

MATERIALS AND METHODS

Retrospective review of 100 paranasal sinus Computed Tomography (CT) scans were done using 64 row Multi Detector Computed Tomography (MDCT). Multiplanar reformation images were assessed for ONC relation to posterior ethmoid and sphenoid sinuses, wall dehiscence, and Pneumatization of Anterior Clinoid Process (PACP).

RESULTS

200 optic nerve canals were assessed and grouped into four types based on the modification of Delano et al., classification. The most common OCN was Type-1 (60%), followed by Type-2 (15%), Type-3 (14%) and Type-4 (11%). Dehiscence was seen in 35(17.5%) mostly in Type-3 canals. PACP was seen in 30 (15%).

CONCLUSION

Knowledge of ON relationship to posterior paranasal sinuses will reduce the devastating complications during sinus surgeries. Our modified ONC classification is based on the bony canal morphology and the degree of protrusion into sinuses. As with other reported studies worldwide, Type-1 ONC is the commonest among the Indians also. Type-2 and 3 ONC with sinus wall dehiscence and PACP are the most important anatomical variations which may potentially predispose to risk of surgical injury to the optic nerves.

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.

Markers of increased aeration in the paranasal sinuses and along the skull base: association between anatomic variants

BACKGROUND

There may be substantial variation in paranasal sinus pneumatization across patients and between right and left sides. Patients with extensive sinus aeration, especially of the sphenoid sinus and along the skull base, often have protrusion of critical structures into the pneumatized sinus cavities, which potentially places these structures at risk during sinus surgery.

OBJECTIVE

To evaluate associations between anatomic markers of increased paranasal sinus aeration along the skull base and to determine whether the presence of certain markers predicts other critical anatomic variants.

METHODS

Submillimeter axial computed tomography (CT) scans and associated triplanar reconstructions from 100 subjects were reviewed for the presence of 22 anatomic variants by two separate evaluators. Twelve of these variants were selected as markers of increased pneumatization. Average numbers of markers were compared with t-tests; associations between markers were evaluated by logistic regression analyses. The Holm-Bonferroni method was used to correct for multiple tests.

RESULTS

Five anatomic variants were associated with increased paranasal sinus pneumatization, as defined by total number of markers of pneumatization: anterior ethmoid artery below the skull base, dehiscent/protruding internal carotid artery (ICA), dehiscent/protruding optic nerve (ON), pneumatized pterygoid recess, and middle turbinate (MT) concha bullosa (all p < .02). Significant associations were found between pneumatized pterygoid recesses and dehiscent or protruding ONs (odds ratio [OR] 3.06, p = .0120), dehiscent or protruding ICAs (OR 6.64, p < .0001), and anterior ethmoid arteries below the skull base (OR 2.65, p = .0189). Significant association was also found between dehiscent or protruding ONs and dehiscent or protruding ICAs (OR 3.57, p = .0047).

CONCLUSION

The markers of increased pneumatization and anatomic associations identified in this study have important implications for surgeons planning and undertaking operative approaches in and around the sinuses.

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

The sphenoid sinus, one of the posterior groups of sinuses, has long been regarded as a 'neglected sinus' due to the anatomical location, poor understanding and poor accessibility, till the advent of endoscopes and modern imaging techniques. Increasing knowledge and greater understanding of this sinus has permitted an evolution in surgical practices and boundaries. Various literatures of the past report a great variety of rates of pneumatization, rates of optic nerve protrusion and dehiscence, as well as internal carotid artery (ICA) protrusion and dehiscence. One similarity noted among these studies is that the rates vary according to the ethnicity of the patients. Recommendations have also been made along the way with regard to modified surgical techniques. This review aims to describe the pneumatization of sphenoid sinus and the topographical relation of the optic nerve and ICA in different populations.

Risks and medico-legal aspects of endoscopic sinus surgery: a review

The aim of this study was to perform a systematic literature review of risks and medico-legal aspects of endoscopic sinus surgery. The development of sophisticated technologies and instruments for endoscopic sinus surgery (ESS) has caused a dramatic increase in the number of otolaryngologists performing sinus surgery and the number of cases performed. This expansion was accompanied by an increase in malpractice lawsuits. Over the past 20 years, rhinology claims represented 70 % of the total indemnity compensation for otolaryngology claims and ESS was the surgical procedure most often involved. Only then will a careful analysis and assessment of the possible and potential risk factors of ESS, which may mislead the surgeon, allow a correct clinical risk management, with activities and procedures aimed at reducing the possibility of complications that may expose the physician to a malpractice suit.

Anatomical variation of the extracranial course of the optic nerve in the floor of the sphenoid sinus: first reported case

OBJECTIVE

We report a unique case of anatomical variation of the extracranial course of the optic nerve running in the floor of the sphenoid sinus.

METHOD

Clinical and radiological findings are presented.

RESULTS

A 39-year-old woman with Turner syndrome presented with severe headache associated with visual disturbances. Magnetic resonance imaging revealed a mass presumed to be a sella meningioma. Computed tomography of the paranasal sinuses was undertaken to help plan surgical removal via an endoscopic trans-sphenoidal approach; this scan revealed an atypical extracranial course of the optic nerve, running in the floor of the sphenoid sinus.

Analysis of pneumatization and neurovascular structures of the sphenoid sinus using cone-beam tomography (CBT)

BACKGROUND

The sphenoid sinus is a frequent target of paranasal sinus surgery. Because of the high risk of injuring the surrounding structures (e.g. internal carotid artery, optical nerve) a preoperative imaging is absolutely necessary.

PURPOSE

To analyze the possibilities of cone-beam computed tomography (CBCT), which is especially quite a new technique in ENT, in the evaluation of the sphenoid sinus, its surrounding structures, and the corresponding anatomical variations.

MATERIAL AND METHODS

This was a retrospective, single-centre study of 580 patients (1160 sides = cases). The Accu-I-Tomo-F17 was used. Pneumatization of sphenoid sinus, course of internal artery, course of optical nerve, and dehiscence of the bony canals were evaluated.

RESULTS

In the case of pneumatization a type I (completely missing or minimal sphenoid sinus) was found in two patients (0.3%), type II (posterior wall of sphenoid sinus is in front of the anterior wall of the sella) in 38 patients (6.6%), type III (posterior wall is between anterior and posterior wall of sella) in 332 patients (57,2%), type IVa (posterior wall is behind the posterior wall of sella without air dorsal the sella) in 104 patients (17.9%), and type IVb (similar to type IVa but with air dorsal the sella) in 104 patients (17.9%). In 1025 cases (89.5%) a smooth course of the internal carotid artery was found whereas a free course could be detected in 120 cases (10.5%). Defects of the bony canal of the optical nerve were found in 16.7% and of the internal carotid artery in 2.7% of the cases. The optical nerve showed a free course through the sphenoid in 151 cases (13.7%) and a smooth course in 1007 cases (87.0%).

CONCLUSION

CBCT could evaluate all relevant anatomic structures and answer the questions of different anatomical variants. A modified classification of the pneumatization of the sphenoid sinus could be described. Frequencies of anatomical variations are in accordance with the current literature of CT research.

[Complications from sinonasal surgery]

Endoscopic sinonasal surgery is the main procedure in sinonasal pathology. Complications are rare but potentially severe given the close relationship between the nasal cavities and sinuses and the orbit, skull base and carotid arteries. The different types of surgeries along with the mechanisms of injury, presenting signs and symptoms, and imaging features of the different surgical complications will be reviewed. We will also review the anatomical variants increasing the surgical risk that radiologists should describe on preoperative imaging studies.

Morphometric analyses of the development of nasal cavity in human fetuses: an anatomical and radiological study

OBJECTIVE

It was aimed to research the morphometric development of the nasal cavity with dissection and radiological scanning methods and to detect anatomical variations.

DESIGN

Retrospective study.

SETTING

Departments of Anatomy and Radiology, Meram Medical Faculty, Selcuk University.

PATIENTS

Dissection stage was performed on 80 spontaneously aborted fetuses (40 males and 40 females) (63 second trimesters and 17 third trimesters) between 13 and 40 weeks of gestation. Radiological scanning stage was carried out on 40 spontaneously aborted fetuses (19 males and 21 females) (12 second trimesters and 28 third trimesters) with multi-detector computed tomography.

METHODOLOGY

One hundred and sixty nasal cavities and related structures were examined by means of bilateral dissection. Reference images were obtained in the axial plane with 3-mm collimation using multi-detector computed tomography (MDCT; Sensation 64, Siemens, Erlangen, Germany). These reference images were sent to the workstation (Leonardo, Siemens, Germany) and three-dimensional (axial, sagittal, and coronal) reformatted images with 1mm thickness were obtained via multiplanar imaging method.

RESULTS

In the dissected fetuses 16 suprema nasal conchae were determined. Six (15%) NSDs (four towards the left and two towards the right) were detected on radiological sections. The angle between the virtual line from sphenoidal sinus ostium through limen nasi and the horizontal plane was 32.72+/-3.3 degrees on average.

CONCLUSION

It was thought that some anatomic variations (e.g. suprema nasal concha, nasal septum deviation) occur in the fetal period; however, other certain differences (e.g. Onodi, Haller, and Agger nasi cells, concha bullosa) might be with effects of environmental factors (trauma and chronic infections) in postnatal period.

Prevention and management of complications in sphenoidotomy

Endoscopic sphenoidotomy is a common surgical procedure that often accompanies routine sinus surgery. Safe completion of a sphenoidotomy depends on a thorough understanding of the surrounding anatomy, reviewing preoperative imaging, and maintaining intraoperative orientation. Intraoperative complications include local hemorrhage, catastrophic hemorrhage caused by internal carotid injury, optic nerve injury, and CSF leak. Postoperative complications tend to be less severe and include postoperative stenosis and mucocele formation. Regarding surgery of the sphenoid sinuses, the best management of complications truly is prevention, making pre- and intraoperative vigilance vital to a successful outcome.

Anatomical variations of neurovascular structures adjacent sphenoid sinus by using CT scan

The aim of this research was to study of the relationship between anatomical variations of neurovascular structures adjacent sphenoid sinus with sex and position of appearance by using CT scan. In this retrospective study paranasal sinuses CT scan has been taken from 399 patients (210 male, 189 female) that referred to Imam Khomeini and Apadana Hospitals, Ahwaz, Iran. Furthermore, protrusion and dehiscence of Internal Carotid Artery (ICA), Maxillary Nerve (MN), Vidian Nerve (VN) and Optic Nerve (ON) into the sphenoid sinuses cavity have been investigated by using CT scan results. In 210 male patients the protrusion of interested variables were noticed as: ICA in 102 (48.5%) cases, ON in 80 (38%) cases, MN in 74 (35.5%) cases, and VN in 60 (28.5%) cases, respectively. Also in 189 female patients group the protrusion of ICA, ON, MN, VN were noticed in 65 (34.3%), 66 (34.9%), 62 (32.8%) and 43 (22.7%) cases, respectively. The statistical analysis show significant difference (p = 0.001) of protrusion of ICA between male and female groups. In 210 male patients the dehiscence of ICA, ON, MN, VN were noticed in 82 (39%), 60 (28.5%), 60 (28.5%) and 66 (31.4%) cases, respectively. Also in 189 female patients the dehiscence of interested variables were noticed as: ICA in 85 (44.9%), ON in 87 (46%), MN in 69 (36.5%), VN in 71 (37.5%) cases, respectively. The statistical analysis show significant difference (p = 0.03) of dehiscence of on variable in male and female groups. In order to increase the risk of intra-operative complications detailed preoperative investigation of neurovascular structures in sphenoid sinuses by use of CT scan images should be done properly.

Anatomic Variation of Sphenoid Sinus and Related Structures in Libyan Population: CT Scan Study

Background

Sphenoid sinus is the most inaccessible paranasal sinus, enclosed within the sphenoid bone and intimately related to numerous vital neural and vascular structures. Anatomic variation of the sphenoid sinus is well documented and may complicate surgery in such a place.

Objective

To outline the surgically risky anatomic variants of the sphenoid sinus as well as the variable relationships between the sinus and related neurovascular structures, for the safe removal of intrasphenoid and pituitary lesions.

Materials and Methods

We undertook a prospective review of 300 paranasal sinus CT scans of Libyan patients; coronal CT scans were obtained by special parameter techniques. We assessed pneumatization of pterygoid process (PP), anterior clinoid process (ACP), and greater wing of sphenoid (GWS); we also examined protrusion and dehiscence of internal carotid artery (ICA), optic nerve (ON), maxillary nerve (MN), and vidian nerve (VN) into the sphenoid sinus cavity.

Results

Pneumatization of PP, ACP, and GWS were seen in 87 (29%), 46 (15.3%), and 60 patients (20%), respectively. Protrusion of ICA, ON, MN, and VN were noticed in 123 (41%), 107 (35.6%), 73 (24.3%), and 81 patients (27%), respectively; dehiscence of these structures was encountered in 90 (30%), 92 (30.6%), 39 (13%), and 111 patients (37%), respectively. Statistically, there was a highly significant association between ACP pneumatization and ICA protrusion, ACP pneumatization and ON protrusion, PP pneumatization and VN protrusion; and GWS pneumatization and MN protrusion (p-value < 0.001).

Conclusion

The sphenoid sinus is highly variable; this variability necessitates a comprehensive understanding of the regional sphenoid sinus anatomy by a detailed CT scan sinus examination before surgery in and around the sinus. This study indicates the possibility of a racial anatomical variation of the sphenoid sinus in the Libyan population.

Anatomical variations in pneumatization of the anterior clinoid process

OBJECT

An anterior clinoidectomy can provide enormous benefits, facilitating the management of paraclinoid and upper basilar artery lesions, but it also carries the potential risk of cerebrospinal fluid leaks. The aim of this study was to assess the variation in the pneumatization of the anterior clinoid process (ACP) in an attempt to reduce the complications associated with an anterior clinoidectomy.

METHODS

The authors analyzed the anatomical variations in the pneumatization of the ACP and optical strut (OS) in 600 sides of 300 consecutive patients by using multidetector-row computed tomography (CT). Computed tomography scans with a 0.5-mm thickness were obtained, and coronal and sagittal reconstructions of the images were displayed in all cases. Pneumatization of the ACP was found in 9.2% of all sides. The origin of pneumatization was the sphenoid sinus in 81.8% of all the sides, the ethmoid sinus in 10.9%, and both of these sinuses in 7.3%. Pneumatized patterns were divided into three groups according to the route: 74.5% were Type I, in which pneumatization occurred via the OS; 14.5% were Type II, pneumatization via the anterior root (AR); and 10.9% were Type III, pneumatization via both the OS and the AR. The origin of pneumatization and the pneumatization pattern showed statistical dependence (p < 0.001). Pneumatization of the OS beyond its narrowest point was found in 6.8% of all sides.

CONCLUSIONS

An awareness of the different variations in pneumatization can prevent destruction of the mucous membrane and facilitate orientation during reconstruction with cranialization. During an anterior clinoidectomy, preoperative CT assessments are necessary to evaluate pneumatization of the ACP.

The "yo-yo" technique to prevent cerebrospinal fluid rhinorrhea after anterior clinoidectomy for proximal internal carotid artery aneurysms

OBJECTIVE

Resection of the anterior clinoid process is important for the exposure of aneurysms on clinoidal and supraclinoidal segments of the internal carotid artery. Cerebrospinal fluid (CSF) rhinorrhea can complicate anterior clinoidectomy when the optic strut is pneumatized and its removal communicates the subarachnoid space with the sphenoid sinus. We present a technique for repairing this defect and preventing CSF rhinorrhea.

METHODS

A suture is secured around a strip of temporalis muscle, which is then pushed through the opening in the optic strut completely into the sphenoid sinus. The ends of suture that trail the muscle are used to retract the muscle from the sphenoid sinus back into the optic strut. The suture is trimmed and the repair is covered with sealant or fibrin glue.

RESULTS

During an 8-year period in which 127 patients with proximal internal carotid artery aneurysms that required anterior clinoidectomy were treated, pneumatized optic struts were encountered in 14 patients (11%). Four patients were treated with the "yo-yo" technique, none of whom experienced CSF rhinorrhea. Before using this technique, 10 patients were managed with standard packing techniques (wax, muscle, and gel foam) and four of these patients subsequently experienced CSF rhinorrhea (40%). In these four patients, all required reoperation with either craniotomy and packing with pericranium (one patient), Couldwell-Luc procedure (one patient), or endoscopic transnasal obliteration of the sphenoid sinus with fat (two patients).

CONCLUSION

The "yo-yo" technique of tightly wedging a muscle plug into the optic strut proved to be simple, fast, and effective, preventing CSF rhinorrhea in all patients in whom it was applied. Although experience with this technique is limited, reversing the direction of packing and pulling muscle from the sphenoid sinus into the optic strut eliminated a complication that occurred in 40% of patients with standard packing techniques.

Risky anatomic variations of sphenoid sinus for surgery

We searched for the surgically risky anatomic variations of sphenoid sinus and aimed to compare axial and coronal tomography in detection of these variations. Fifty-six paranasal tomography images (112 sides) were evaluated for coronal, axial and both coronal and axial images. Tomographic findings including bony septum extending to optic canal or internal carotid artery; protrusions and dehiscences of the walls of internal carotid artery, optic nerve, maxillary nerve and vidian nerve; extreme medial course of internal carotid artery; patterns of aeration of the anterior clinoid process; and Onodi cells were evaluated. The results were classified as "present, absent, suspicious-thin (only for dehiscence) or no-consensus". The results of each plane were compared with that of the result of the both planes together. Kappa coefficient and Chi-square tests were used to compare both planes. Twelve cadaveric dissections were performed to reveal the proximity of sphenoid sinus to surgically risky anatomic structures. Endoscopy was applied to five cadavers. 18 evaluations were classified as 'no-consensus'. We detected 34, 35, 34 and 40 protrusions of internal carotid artery, optic nerve, maxillary nerve, vidian nerve, respectively. Dehiscences were present in 6, 9, 4 and 8, and suspicious-thin in 8, 10, 16 and 25 in canals of internal carotid artery, optic nerve, maxillary nerve and vidian nerve, respectively. Bony septum to internal carotid artery and optic nerve was observed in 30 and 22 cases. We observed 9 extreme medial courses of internal carotid artery, 27 aerated clinoid process and 9 Onodi cells. Axial images were superior in detection of bony septum to internal carotid artery and Onodi cells; while the coronal images were more successful in detection of protrusion of optic nerve and vidian nerve, and dehiscense of maxillary nerve and vidian nerve (P<0.05). In cadaveric dissections, the septa were inserted into the bony covering of the carotid arteries in two sinuses (8.3%). Detailed preoperative analysis of the anatomy of the sphenoid sinus and its boundaries is crucial in facilitating entry to the pituitary fossa and reducing intraoperative complications. Coronal tomography more successfully detects the sphenoid sinus anatomic variations.

Orbital complications of functional endoscopic sinus surgery: MR and CT findings

AIM

To describe the radiological findings of ophthalmic complications during functional endoscopic sinus surgery (FESS) and correlate them with the clinical manifestations and mechanisms of injury.

METHODS

This was a retrospective review of the clinical and cross-sectional imaging findings of 9 patients with orbital complications during FESS.

RESULTS

The most common site of entry into the orbit during FESS was the lower medial orbital wall (7 of 9), followed by the inferior orbital wall, resulting in injury to the medial rectus (4 of 9) and, less frequently, the inferior rectus (2 of 9) or superior oblique muscles (1 of 9). Extensive scarring on imaging (3 of 9) was associated with global ocular motility dysfunction. In contrast, localized scarring (3 of 9) or extraocular muscle trauma (6 of 9) resulted in disturbance of eye movement in the direction of gaze from the injured site.

CONCLUSIONS

Orbital magnetic resonance and computed tomography findings correlate very well with the abnormal eye movements clinically observed, and can assist in clarifying the cause of injury and guide surgical corrective management of patients suffering orbital complications from FESS. Radiologists should be familiar with the recent developments in FESS instrumentation as well as with the most commonly injured structures within the orbit.

Software-enabled CT analysis of optic nerve position and paranasal sinus pneumatization patterns

OBJECTIVE

Delineate the relationships among the optic nerve (CN II), the sphenoid sinus, and the sphenoethmoid cell.

STUDY DESIGN

High-resolution CT scans of 64 frozen human cadavers were obtained on a Siemens VolumeZoom CT scanner (Munich, Germany) and transferred to a CBYON Suite Doctor Station version 2.6 (CBYON, Mountain View CA) for standardized review.

RESULTS

Pneumatization around CN II was categorized into 5 types: no adjacent pneumatization (type 0), pneumatization adjacent to CN II (type 1), adjacent pneumatization with indentation (type 2), pneumatization of <50% CN II circumference (type 3), and pneumatization of >50% CN II circumference (type 4). The prevalence of types 0 to 4 CN II position relative to the sphenoid sinus was 4.7%, 25.8%, 39.8%, 14.1%, and 15.6%, respectively. The prevalence of sphenoethmoid cells was 28.1%. The prevalences of types 0, 1, 2, 3, and 4 CN II positions relative to the sphenoethmoid cell was 5.6%, 58.3%, 25%, 2.8%, and 8.3% respectively.

CONCLUSIONS

Software-enabled CT review facilitated precise study of the anatomic relationships of CN II. Caution must be exercised during sinonasal surgery to minimize the risk of inadvertent CN II injury.

EBM RATING

D.

Remarkable anatomic variations in paranasal sinus region and their clinical importance

With the advent of functional endoscopic sinus surgery (FESS) and coronal computed tomography (CT) imaging, considerable attention has been directed toward paranasal region anatomy. Detailed knowledge of anatomic variations in paranasal sinus region is critical for surgeons performing endoscopic sinus surgery as well as for the radiologist involved in the preoperative work-up. To be in the known anatomical variants with some accompanying pathologies, directly influence the success of diagnostic and therapeutic management of paranasal sinus diseases. A review of 512 (1024 sides) paranasal sinus tomographic scans was carried out to expose remarkable anatomic variations of this region. We used only coronal sections, but for some cases to clear exact diagnosis, additional axial CT scan, magnetic resonance imaging (MRI) and nasal endoscopy were also performed. In this pictorial essay, rates of remarkable anatomic variations in paranasal region were displayed. The images of some interesting cases were illustrated, such as the Onodi cell in which isolated mucocele caused loss of visual acuity, agger nasi cell, Haller's cell, uncinate bulla, giant superior concha bullosa, inferior concha bullosa, bilateral carotid artery protrusion into sphenoid sinus, maxillary sinus agenesis, bilateral secondary middle turbinate (SMT) and sphenomaxillary plate. The clinical importance of all these variations were discussed under the light of the literature. It was suggested that remarkable anatomic variations of paranasal region and their possible pathologic consequences should be well defined in order to improve success of management strategies, and to avoid potential complications of endoscopic sinus surgery. The radiologist must pay close attention to anatomical variations in the preoperative evaluation.

Relação anatômica do nervo óptico com o seio esfenoidal: estudo por tomografia computadorizada

O seio esfenoidal entre os seios da face é certamente o mais negligenciado quanto ao diagnóstico. A abordagem cirúrgica requer conhecimento anatômico detalhado, levando-se em conta as graves complicações decorrentes de lesões de estruturas vitais adjacentes a esta região. OBJETIVO: O objetivo do nosso estudo é avaliar a relação anatômica do canal do nervo óptico com o seio esfenoidal utilizando a tomografia computadorizada. FORMA DE ESTUDO: Análise de série. MATERIAL E MÉTODO: Os autores apresentam a análise retrospectiva de 202 tomografias computadorizadas de seios da face de indivíduos de ambos os sexos com idade igual ou superior a 14 anos. Os exames foram avaliados observando o trajeto do canal do nervo óptico obtido pelo grau de projeção na parede do seio esfenoidal. Foi utilizada a classificação modificada de Delano. Foi avaliada a ausência de atenuação óssea (deiscência) do canal do nervo óptico no seio esfenoidal. O grau de pneumatização do seio esfenoidal foi analisado, sendo empregado a classificação de Hammer's adaptada por Guerrero, além da pneumatização do processo clinóide anterior e pterigóide e a presença da célula de Onodi. RESULTADOS: A maioria dos pacientes (78.96%) apresentou o canal do nervo óptico com trajeto do tipo 1, o tipo 2 foi observado em 16.83%, o tipo 3 em 3.47% e o tipo 4 em 0.74%. A presença de deiscência do nervo óptico na parede do seio esfenoidal foi evidenciada em 21.29% dos casos. Em relação à pneumatização, notamos que o tipo pré-selar foi observado em 6.44%, o tipo selar em 39.11%, o tipo selar em 54.45%, e o tipo apneumatizado não foi observado em nossos casos. A pneumatização do processo clinóide anterior foi constatado em 10.64% enquanto do processo pterigóide em 21.29% dos casos, a célula de Onodi foi verificada em 7.92% dos casos. CONCLUSÃO: A presença de deiscência do canal do nervo óptico está relacionado com o grau de pneumatização dos processos clinóide anterior e processo pterigóide, a presença de célula de Onodi e os tipos de trajeto 2, 3 e 4 da relação do nervo óptico com o seio esfenoidal.

Ophthalmic complications of endoscopic sinus surgery

The intimate anatomical relationship between the orbit and the paranasal sinuses places the orbit and its contents at risk of harm from primary pathologic processes of the sinuses. In the absence of ophthalmic signs or symptoms, ophthalmologists are not routinely involved in the management of patients with sinus disease. Occasionally, some patients may develop ophthalmic complaints after surgical intervention. The orbit, optic nerve, extraocular muscles, and lacrimal drainage system are susceptible to injury during endoscopic sinus surgery. The risk of injury is related to the skill of the sinus surgeon, history of previous surgery, extent and severity of disease, and anatomic variation. Furthermore, recent advances in endoscopic sinus surgery, in particular the use of powered cutting instruments, has resulted in a novel mechanism of injury to the ocular structures.

Radiation dose to the lenses in CT of the paranasal sinuses

The radiation dose to the lens during CT of the paranasal sinuses was measured in 20 patients. In 10 patients, a "standard" technique with axial and coronal sections was used. In the remaining 10 patients, overlapping axial sections for bidimensional reconstruction were obtained. Radiation dose was measured using thermoluminescent dosimeters. The mean dose was 22 mGy in patients who underwent "standard" CT and 42 mGy in those who underwent CT with overlapping sections. Dose was dependent on the total number of slices and of transorbital axial sections. Coronal sections did not statistically increase the radiation dose to the lenses. Although these doses were significantly below the critical dose for cataracts, CT with overlapping sections gives a considerably higher radiation dose. We recommend the bidimensional reconstruction technique only for selected cases (e.g. preoperative assessment of the roof of the ethmoid sinuses or in patients who can or should not maintain the hyperextended position required for coronal views.