Sphenoethmoidal Cell Research Articles

Magnetic Resonance Imaging Features of the Sphenoid Sinus in Patients with Non-Functioning Pituitary Adenoma.

Background and Objectives: A magnetic resonance imaging (MRI) scan is part of the diagnostic protocol in pituitary adenoma patients. The goal of the present study is to present and analyse the MRI appearances of the sphenoid sinus (SS) in patients with non-functioning pituitary adenoma (NFPA). Materials and Methods: This is a retrospective case-control study conducted between January 2015 and December 2023 in a tertiary referral hospital. Forty NFPA patients were included in the study group, while the control group consisted of 30 age- and gender-matched cases. Results: The sellar type of SS pneumatization was the most frequently encountered pattern among both groups. The presence of the lateral recess of the SS, mucosal cysts, and sphenoethmoidal cells was similar in both patient groups. The proportion of patients with SS mucosal thickness greater than 3 mm was 42.5% in NFPA group and 3% in the control group, and this difference was statistically significant (p < 0.001). The space between the two optic nerves was significantly larger in the NFPA group as compared to the control group (p < 0.001). Conclusions: Our study was able to establish a statistically significant association between the presence of NFPA and both the thickening of the SS mucosa and increased space between optic nerves.

CT Scans Imaging of Human Ethmoid Sinuses and Gross Anatomical Dissection: a Descriptive, Projective, Comparative, and Dimensional Study

Introduction: The ethmoid air sinus can subdivide into several air cells, which are separated from each other by thin, incomplete bony septa resulting in the formation of three groups of air cells (anterior, middle, and posterior cells). Methods: A randomized sample of 360 human individuals, including 110 cadavers with another 250 CT scan cases, was achieved from February 2020 to November 2021. Results: The agger nasi was the most common type of cell demonstrated by 81.8% in cadaveric cases and 94% in CT cases. The frontal bulla cell presents just above the ethmoidal bulla and may produce convexity on the frontal sinus floor. Its prevalence was 10.9% in cadaveric cases and 22.8% in CT cases. The suprabullar cell is on top of bulla ethmoidalis and represents 7.3% of cadaveric cases and 14.8% of CT cases. Concha bullosa presents as a comprehensive pneumatization in the middle turbinate. Its prevalence was 34.5% in cadaveric cases and 44% in CT cases. The Haller cell reveals as a pneumatized air-filled cell shown at the lower medial side of the orbit. It was in 29% of cadaveric cases and 42% of CT cases. In addition, the sphenoethmoid (Onodi) cell is a posterior ethmoidal cell with a prevalence of 41.8% in cadaveric and 64% in CT cases. Conclusion: This study described the morphologic anatomy of each ethmoid sinus and compared its dimensions by gross anatomy with CT scanning in different age groups. This yields clues to understanding the variations in human races and ethnic groups

A Case of 40-Year-Old Male with Onodi Cell Mucocele

Sphenoethmoidal (Onodi) cells originate from the ethmoid sinus and are located at the posterior and lateral direction. The obstruction of the sinus ostium leads to the accumulation of mucous fluid and eventually leads to the formation of a mucocele. Onodi cell mucoceles can cause visual loss or disturbance due to the adjacency to the orbital apex. Here we report a case of Onodi cell mucocele with a visual field disturbance, where the patient underwent an endoscopic sinus surgery 12 days after the initial symptom. After 21 days of onset, the subjective symptom started to subside. For Onodi cell mucocele patients with visual disturbance, we recommend rapid diagnosis with computed tomography and early marsupialization of the mucocele.

Long-Term Visual Disturbance Affected by Infraorbital Cell Mucocele and Fully Recovered after Surgical Management: A Case Report

Mucocele of the paranasal sinuses is a benign, expansible, and cystic mass filled with mucous collection. Infraorbital cells are extramural ethmoid cells that develop into the roof of the maxillary sinus and the base of the orbital cavity. Although infraorbital cells are asymptomatic in most cases, inflammation or mucocele in those cells may cause various symptoms including facial pain, hypoesthesia, and secondary rhinosinusitis. They sometimes invade the orbital cavity, which may cause ophthalmic symptoms such as visual disturbance, orbital swelling, and orbital pain. Most of the cases with ophthalmic symptoms are related to sphenoethmoidal cell mucocele. Delayed treatment of more than two days is known to have a poor prognosis for visual disturbances caused by acute optic nerve compression. We describe a case of 61-year-old man who complained of visual disturbance related to infraorbital cell mucocele and fully recovered right after surgical management.

Radiologic Analysis of Balloon Sinuplasty in a Human Cadaver Model: Observed Effects on Sinonasal Anatomy.

Balloon sinuplasty is increasingly used in the outpatient clinic for treatment of chronic rhinosinusitis, but radiologic analysis of its effects on sinonasal anatomy is largely uncharacterized in the known literature. The purpose of this study is to examine the anatomic effects of balloon sinuplasty in a cadaveric model. Five fresh cadaver heads underwent sequential endoscopic balloon dilation of maxillary ostia, frontal recess outflow tracts, and sphenoid ostia bilaterally by fellowship-trained rhinologists. Pre- and post-procedural CT imaging was obtained. CT scans were imported into Mimics™ software and sinonasal anatomy was analyzed systematically. Visual confirmation of balloon dilation was achieved in all 3 sites bilaterally in each cadaver. Radiologic analysis demonstrated that the frontal sinus outflow tract was appropriately dilated 60% (6/10 sites) of the time while the agger was inadvertently dilated 30% of the time (3/10). The sphenoid os was successfully dilated 70% (7/10 sites) of the time. In two cases, a posterior sphenoethmoid (Onodi) cell was dilated instead of the sphenoid. Successful dilation of maxillary os was noted 60% of the time (6/10 sites). No significant change in maxillary os was noted after balloon dilation. Normal middle turbinates were significantly medialized following balloon dilation 75% (6/8 sites) of the time. While the goal of balloon sinuplasty is to improve natural sinonasal drainage by dilating existing outflow tracts, as evidenced by radiologic evaluation the procedure appears not to achieve this in all cases, while occasionally creating unintended changes in sinonasal anatomy as well. These unrecognized changes in anatomy may be responsible for the post-procedure change in symptomatology that some patients experience.

A 16-Year Study on Incidence and Progression of Diseased Sphenoethmoidal (Onodi) Cell.

Traumatic operative injury of the optic nerve in an endoscopic sinus surgery may cause immediate or delayed blindness. It should be cautioned when operating in a sphenoethmoidal cell, or known as Onodi cell, with contact or bulge of the optic canal. It remains unclear how frequent progression to visual loss occurs and how long it progresses to visual loss because of a diseased sphenoethmoidal cell. Research to discuss these questions is expected to help decision making to treat diseased sphenoethmoidal cells. From July 2001 to June 2017, 216 patients received conservative endoscopic sinus surgery without opening a diseased sphenoethmoidal cell. We used their computed tomography images of paranasal sinuses to identify diseased sphenoethmoidal cells that could be associated with progression to visual loss. Among the 216 patients, 52.3% had at least one sphenoethmoidal cell, and 14.8% developed at least one diseased sphenoethmoidal cell. One patient developed acute visual loss 4412 days after the first computed tomography. Our results show that over half of the patients have a sphenoethmoidal cell but suggest a rare incidence of a diseased sphenoethmoidal cell progressing to visual loss during the follow-up period.

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

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. 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. 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. 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.

Anatomic Variations of Paranasal Region in Migraine.

To assess the incidence of anatomical variations of the paranasal region on computed tomography in migraine patients compared with control subjects. Paranasal computed tomography scans of 2 groups consisting of 50 migraine patients and 50 control subjects were evaluated, retrospectively. The presence of anatomic variations and the unilateral or bilateral presence of these variations were noted. Appropriate statistical tests were performed to compare the migraine and control groups, using a threshold P value of 0.05 for statistical significance. The migraine group included 39 female and 11 male patients with mean age of 39.9 (range: 18-65) years. The control subject group included 29 female and 21 male patients with mean age of 41.9 (range: 18-73) years. Anatomic variations noted included nasal septal deviation and spur, paradoxical curvature of middle concha, agger nasi cell, infraorbital ethmoidal (Haller) cells, sphenoethmoidal (Onodi) cells, supraorbital ethmoidal air cells, concha bullosa, uncinate bulla, and pneumatized crista galli. Of these variations, only the presence of Haller cells was statistically significantly higher in the migraine group compared with controls (P = 0.007). The unilateral presence of Onodi (P < 0.001), unilateral presence of supraorbital ethmoidal air cells (P = 0.012), and bilateral presence of concha bullosa (P = 0.016) were statistically significantly higher in the migraine group. There was no statistically significant difference between the unilateral or bilateral presence of Haller cells in migraine patients compared with controls (P > 0.05). Radiographic assessment of the paranasal sinuses is useful to elucidate potential points of pathology in migraine patients. The specific contribution of Haller cells to migraine headache symptoms and safe methods for surgical decompression warrant further study.

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

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). 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. 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. 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.

The supreme turbinate and the drainage of the posterior ethmoids: a computed tomographic study.

It is generally acknowledged that the posterior ethmoidal cells drain under the superior nasal turbinate (SorNT) or, rarely, under the supreme nasal turbinate (SmeNT), and the sphenoid ostium (SO) opens to the sphenoethmoidal recess. However, detailed relations between these structures are variable, complex and still not clear. There is no reliable data on the prevalence of SmeNT and drainage of the posterior ethmoidal cells under this structure. The aim of this study was to re-evaluate the anatomy of the aforementioned region. Multiplanar and three-dimensional reconstruction analysis of 100 thin slice paranasal sinus computed tomography scans. SmeNT was identified in 77 subjects (136 sides). It formed the ostium to the posterior ethmoidal cell adjacent to the skull base or orbit in 58 subjects (91 sides). This cell drained independently from the remaining posterior ethmoidal cells. The sphenoethmoidal (Onodi) cell drained to supreme meatus in 41 subjects (54 sides), and to superior meatus in 37 subjects (49 sides). SO was always located medial to the posteroinferior attachment of SmeNT, or SorNT (in absence of SmeNT). Patients with divergent drainage of the posterior ethmoids (with posterior ethmoidal cell draining to the supreme meatus) may require more extensive surgery to avoid persistence or recurrence of inflammatory disease. SmeNT is more common than thought, but due to its posterior and superior location to SorNT, it is rarely seen intraoperatively. If SmeNT is present, SO is always located medial to its posteroinferior attachment. (Folia Morphol 2018; 77, 1: 110-115).

Sphenoethmoid Cell: The Battle for Places Inside of the Nose Between a Posterior Ethmoid Cell and Sphenoid Sinus: 3D-Volumetric Quantification.

Background: Sphenoethmoid cells may be above the sphenoid sinus with/ or without con-tact to optical nerve. Although sphenoethmoid cells are theoretically considered to possibly influence the sphenoid sinus volume, we could not find any study in the literature on this issue.Aims: The aim of our study was to detect sphenoethmoid cells and measure the sphenoid sinus vol-ume using multiplanar computerized tomography and also investigate the correlation between the presence of sphenoethmoid cells and the sphenoid sinus volume.Methods: Retrospectively 141 patients who had available paranasal computerized tomography images were included in this study. The sphenoid sinus volumes of each patient were calculated individually for each side, and the relationship between the presence of sphenoethmoid cell and sphenoid sinus volume was investigated.Results: Sphenoethmoid cells were detected at 106 (37.5%) of the total 282 sides in 141 patients. No gender difference was observed. The total sphenoid sinus volume was significantly lower in the group of patients who had bilateral sphenoethmoid cells than in the sphenoethmoid cell negative group. In patients with a unilateral sphenoethmoid cell, a significant decrease in the sphenoid sinus volume was observed only for the side where the sphenoethmoid cell was located.Conclusion: It was observed that the sphenoethmoid cells caused a significant reduction in the sphe-noid sinus volume on the side where they were located. In the case of low sphenoid sinus aeration, the sphenoethmoid cell should be kept in mind. Further studies with an extended patient series are required to explore this issue.

The Onodi Cell: An Anatomic Illustration.

This anatomic image demonstrates the sphenoethmoidal (Onodi) cell (a variant of the paranasal sinuses), the identification of which is critical to prevent neurovascular injury during endoscopic approaches to the sella and adjacent regions of the skull base.

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

BackgroundThe 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. ObjectiveTo determine the prevalence and types of Onodi cell in CT examination and find the most suitable CT scanning planes to identify it. Material and methodsThree 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. ResultsThe 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. ConclusionThe 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.

A Good View at Proper Diagnosis: Onodi Cell As Rare Cause of Optic Neuritis

The sphenoethmoidal cell (Onodi cell) is a quite posterior ethmoid cell with more cranial and dorsal extension which leads to dorsal displacement of sphenoidal sinus. Onodi cell shows very close proximity (medial, cranial, and caudal) to the optic canal respectively to the optic nerve.

Role of the superior turbinate when performing endoscopic endonasal transsphenoidal approach

This study examined the relationship between the superior turbinate and natural ostium of the sphenoid sinus, as seen during the endoscopic endonasal transsphenoidal approach (EETSA) for sellar lesions and described how to enter the sphenoethmoid cell safely for complete exposure of the sellar floor, including adjacent vital structures such as the prominence of the optic nerve and carotid artery. This study retrospectively reviewed the medical records and operative findings of 154 patients, who underwent EETSA between February 2009 and February 2011. We evaluated the location of the natural ostium of the sphenoid sinus relative to the superior turbinate and revealed the clinical significance of the superior turbinate as a surgical guide to enter into the sphenoethmoid cell during EETSA. The natural ostium of the sphenoid sinus was located medially to the posteroinferior end of the superior turbinate in 151 (98%) patients. In 1 patient, the natural ostia of the sphenoid sinus were located lateral to the superior turbinate bilaterally. Sphenoethmoid cell was encountered in 53 (34%) patients. We could easily enter the sphenoethmoid cell at the point where the superior turbinate was attached to the anterior wall of the sphenoid sinus. The superior turbinate is a good surgical landmark for identifying the natural ostium of the sphenoid sinus and as a guide for the surgical entrance to the sphenoethmoid cell extending to the sphenoid sinus during EETSA.

Analysis of sphenoid sinus in the operative plane of endoscopic transsphenoidal surgery using computed tomography

Recently, the endoscopic transsphenoidal approach for sphenoid sinus or intracranial lesion has gained more popularity and the study of the surgical anatomy and relationships of the sphenoid sinus has gained increased significance. The aim of this study was to clarify the anatomical features of the sphenoid sinus including surrounding structures as seen in the operative view of endoscopic transsphenoidal surgery. The various distances in the sphenoid sinus as well as the relationships between the sphenoid sinus ostium (SO) and important structures such as the optic canal (OC) and carotid artery (CA) according to the presence of Onodi cell (sphenoethmoidal cell; Onodi group vs. non-Onodi group) were assessed using multiplanar and three-dimensional model of CT scans in 100 patients. The SO was more inferior in Onodi group and located superior to the lowest point of the sella. The horizontal distance from the SO to sella was approximately 13 or 14 mm depending on the existence of Onodi cells. Regardless of Onodi cell, the whole course of the OC in the sinus ran superolaterally to inferomedially in the endoscopic view. However, Onodi cell made the angles from the SO to OC larger. In Onodi group, the CA was located from the SO in a superolateral direction, but in non-Onodi group, the CA was located from the SO in the inferolateral direction. This study provides anatomical information about the sphenoid sinus, with important surgical distances between the SO and surrounding structures measured, which is essential to avoid complications during transsphenoidal surgery.

Radiologic reporting for paranasal sinus computed tomography: A multi‐institutional review of content and consistency

To optimize clinical care, radiologic reporting should consistently include clinically pertinent information. The purpose of this study was to: 1) determine the current satisfaction of otolaryngologists with paranasal sinus computed tomography (CT) radiologic reporting and 2) evaluate the comprehensiveness of paranasal sinus CT radiologic reporting. Two parts: 1) A national survey of all practicing otolaryngologists in Canada and 2) a retrospective review of paranasal sinus CT scan radiologic reporting. A national survey of all Canadian otolaryngologists was conducted in September 2011. Questions were focused on eliciting the current satisfaction with sinus CT radiologic reporting. At two major centers (Alberta Health Services-Calgary Zone and the Ottawa Hospital), all sinus CT scans performed over a 2-year period were identified (9,739), and 100 from each center were randomly selected for analysis. The radiology reports were scrutinized to determine if seven critical and 11 noncritical items were mentioned. Many (22%) otolaryngologists are dissatisfied with current sinus CT radiologic reporting, and the majority (67%) would like more clinically useful information. All predefined sinus CT items were inconsistently reported. Anterior ethmoid artery anatomy, ethmoid skull base integrity, and sphenoethmoidal cell were the most infrequently reported critical items. This study has demonstrated that important information is inconsistently reported for sinus CT, and most otolaryngologists would like to see more clinically relevant content in radiology reports. Optimizing the reporting of sinus CT scans will improve communication between the radiologist and other clinicians managing patients with sinonasal disease. 2b.

Chinook Wind Barosinusitis: An Anatomic Evaluation

Chinook, or föhn, is a weather phenomenon characterized by a rapid influx of warm, high-pressured winds into a specific location. Pressure changes associated with chinook winds induce facial pain similar to acute sinusitis. The purpose of this study was to determine the relationship between sinonasal anatomy and chinook headaches. Retrospective computed tomography (CT) sinonasal anatomy analysis of 38 patients with chinook headaches and 27 controls (no chinook headaches). The chinook headache status was blinded from the CT reviewer. Forty-one sinonasal anatomy variants, Lund-Mackay status, and sinus size (cm(3)) were recorded. There were three statistically significant sinonasal anatomy differences between patients with and without chinook headaches. The presence of a concha bullosa and sphenoethmoidal cell (Onodi cell) appeared to predispose to chinook headaches (p = 0.004). Chinook headache patients had larger maxillary sinus size (right, p = 0.015, and left, p = 0.002). The Lund-Mackay score was higher in the control patients (p = 0.003) indicating that chronic sinusitis does not play a role in chinook headaches. Chinook winds are a common source of facial pain and pressure. This is the first study to show that sinonasal anatomic variations may be a predisposing factor. Anatomic variants may induce facial pain by blocking the natural sinus ostia, thus preventing adequate pressure equilibrium.

Influence of anatomic variations of the middle nasal meathus on sinonasal diseases

The most common anatomic variations of the structures of the middle nasal meatus are variations of agger nasi cells, variations of the middle turbinate, variations of uncinate process, variations of the ethmoidal bulla, deviations and deformations of nasal septum in the region of the middle nasal meatus, Haller's cell (orbitoethmoidal) and Onodi's cell (sphenoethmoidal cell). In 1997, the Otorhinolaryngology-Head Neck Surgery, Task Force on Chronic Rhinosinusitis defined chronic sinusitis and nasal disease initially by including sinusitis and rhinitis with one term-chronic rhinosinusitis. This was done because it was apparent to many that nasal disoders often affected the sinuses, and vice versa. Also they established baseline parameters, major and minor signs and symptoms, for definition of rhinosinusitis. Two major factors or one major factor and two minor factors constitute a strong history for rhinosinusitis. The following methods were used in the study: 1. Anamnestic data processing about: disease symptoms that were recognized by American Academy for ENT as major and minor criteria in diagnosing nosinusitis; the duration of symptoms; the kind of sinonasal disorder and the secondary disorders. 2. Data processing obtained by anterior/posterior rhinoscopy. 3. Data processing obtained by endoscopic examination. 4. Data processing obtained by CT of paranasal cavities and the nose. The data about anatomic variations were statistically processed by Eives's correlation coefficient that indicates the degree of correlation between sinonasal disorders and anatomic variation. By analyzing the obtained data in the examined patients with sinonasal disorders, anatomic variations were present in over 50% of the patients and are defined by percentage. 1. The deviation of nasal septum in 83.33% patients. 2. The variations of the form of the middle nasal chonha in 58.92% patients. 3. The presence of agger nasi cells in 50% patients. 4. Variations of the form of ethomoidal bulla in 50% patients. Eives's correlation coefficient i.e. the degree of correlation between sinonasal disorders and the presence of anatomic variation statistically significantly correlate at r > or = 0.05 of anatomic variation of the middle nasal chonha (r = 0.23) and the presence of deviation/deformation of nasal septum (r = 0.6) with sinonasal disorders. Anatomic variations of the structures of the middle nasal meatus can additionally complicate the anatomy of the lateral nasal wall and the conditions of the ostiomeatal unit. Therefore we must view these variations as factors predisposing to more rapid and frequent appearance and persistence of chronic inflammations. Also, familiary with the variations in sinonasal anatomy is a prerequisite to safe and effective surgical treatment of sinonasal disease. Recognition of this anatomic variation should minimize catastrophic violation of vital structures such as orbit or skull base.

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

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