Olfactory Fossa and New Angle Measurements: Lateral Lamella-Cribriform Plate Angle

The Effects of Nasal Septal Deviation on Anterior Skull Base Parameters

Introduction  Functional endoscopic sinus surgery and endoscopic skull base surgery are frequently performed surgeries today. Nasal septal deviation is a common finding and can affect the surgical area. Therefore, it is important to examine the effect of this deviation on other anatomical structures. Objectıve  The aim of the present study was to determine whether there is a relationship between the degree of nasal septal deviation and anterior skull base structures using computed tomography (CT). Methods  A total of 312 patients (aged 18 to 65 years old) whose paranasal sinus CT images were available were included in the study. Measurements were obtained on images retrieved from Picture Archiving and Communication System (PACS) and Horos image archive systems in the bone window in the coronal and axial plane. Results  The mean age of 312 patients was 33.00 years old (standard deviation [SD] 11.22 years). The presence of septal deviation was not associated with changes in olfactory fossa (OF) depths, Keros degrees, and the angle between the lateral lamella and the cribriform lamella. However, OF depths and Keros degrees on the deviated side of the septum were found to change at a significant level ( p  < 0.05). No significant association was observed between the degree of septal deviation and cribriform lamella-lateral lamella angle. Conclusion  The study showed significantly increased OF depth and Keros degree on the deviated side of the nasal septum. Performing CT scans before endoscopic sinus surgery and endoscopic skull base surgery is important to increase the chances of a successful surgical outcome and to reduce complications.

Anatomic Parameters and Growth of the Pediatric Skull Base: Endonasal Access Implications

Objectives: Endoscopic endonasal anterior skull base surgery has expanding use in the pediatric population, but the anatomy of pediatric patients can lead to limitations. This study aims to characterize the important anatomical implications of the pediatric skull base using computed tomography (CT) scans. Design: Retrospective analysis Setting: Tertiary academic medical center Participants: 506 patients aged 0-18 who had undergone maxillofacial and or head CTs between 2009-2016. Methods: Measurements included piriform aperture width, nare to sella distance (NSD), sphenoid pneumatization, olfactory fossa depth, lateral lamella cribriform plate angles, and intercarotid distances (ICD) at the superior clivus and cavernous sinus. These patients were then subdivided into 3 age groups adjusting for sex. ANCOVA models were fit comparing between all age groups and by sex. Results: Piriform aperture width, NSD, sphenoid sinus pneumatization as measured using lateral aeration and anterior sellar wall thickness, olfactory fossa depth, and ICD at the cavernous sinus was significantly different among all age groups (P<0.0001). Our results show that mean piriform aperture width increased with each age group. The mean olfactory fossa depth also had consistent age dependent growth. In addition, ICD at the cavernous sinus showed age dependent changes. When comparing by sexes, females consistently showed smaller measurements. Conclusion: The process of skull base development is age and sex dependent. During preoperative evaluation of pediatric patients for skull base surgery piriform aperture width, sphenoid pneumatization in both the anterior posterior and lateral directions, and ICD at the cavernous sinus should be carefully reviewed.  

Ethmoid roof morphometric measurements of a pediatric population using computed tomography

OBJECTIVE

To reveal the anatomical relationships of the ethmoid roof on CT in pediatric case group.

METHODS

We measured the depth of olfactory fossa (DOF), the width of olfactory fossa (WOF), the angle between lateral lamella and cribriform plate (LLCPA), the width of the olfactory cleft (WOC), the length of lateral lamella (LLL), orbital roof fovea to ethmoidal distance (ORFED) and orbital roof to cribriform plate distance (ORCPD) and we determined Keros and LLCPA types from paranasal sinus CT of subjects under 16 years of age retrospectively.

RESULTS

The incidence of Keros type I was higher in females and Keros Type II in males. The ORCPD, DOF and LLL values were found to be higher in 13-16 years age group and WOF and LLCPA in 4-6 years age group. The prevalence of Keros type II was higher in the 13-16 age group, and Keros type I was higher in other age groups. LLCPA type A was the most frequent in all age groups and in both sexes. There was a positive correlation between age and ORCPD, DOF, LLL, and a negative correlation with ORFED, WOF, LLCPA. Olfactory fossa width and depth had a negative correlation. LLCPA had a positive correlation with WOF and a negative correlation with DOF. There was a positive correlation between LLCPA and LLL. DOF and LLL had a positive correlation too.

CONCLUSIONS

Paranasal sinus CT provides useful information about frontal skull base anatomic relations before sinus surgery in pediatric cases.

The important adjacent structures for anterior ethmoidal artery in FESS: Anterior ethmoidal artery canal angle, supraorbital ethmoid cells and Keros classification

OBJECTIVES

This study investigated the visualization of the anterior ethmoidal artery (AEA) as notch, canal and sulcus, its relationship between supraorbital ethmoid cells (SOECs) and the Keros classification of the olfactory fossa on paranasal sinus computerized tomography (PNSCT).

METHODS

In this retrospective study, the paranasal sinus computerized tomography (PNsCT) images of 204 patients (103 males and 101 females) were analyzed. AEA canal, notch and sulcus, SOECs, the distance between AEA notch and ethmoid roof, AEA canal angle and Keros classification of the olfactory fossa were evaluated.

RESULTS

AEA notch in all patients and AEA canal (37.6 to 45.6%) and AEA sulcus (53.5 to 61.2%) were visualized. In the AEC canal and sulcus visualized patients, the Keros classification revealed higher. AEA notch and ethmoid roof distance increased in patients with higher Keros types. The presence of SOECs was significantly higher in males (41.7%) than females (19.8%) on the left side. There was a positive correlation between SOEC presence and Keros classification. In patients with SOEC, bilateral AEA canal and sulcus visualized more; and bilateral AEA notch and ethmoid roof distance increased. On the right side, the AEA canal angle of the males was significantly higher than that of the females. In patients with SOEC, the left AEA canal angle also increased.

CONCLUSION

When detected SOECs and higher Keros types, the AEA was detected away from the skull base, AEA notch-ethmoid roof distance increased; and the AEA canal angle increased. To avoid intracranial penetrations, PNSCT should be evaluated carefully during the preoperative period.

Radiological Evaluation of Olfactory Fossa with Cone-Beam Computed Tomography

Objectives

The aim of this retrospective study was to evaluate the morphology of the olfactory fossa in the Turkish population using cone-beam computed tomography according to Keros classification and to investigate the effect of age, gender and nasal septum deviation on the olfactory fossa.

Material and Methods

Olfactory fossa (OF) were analysed in coronal sections on cone-beam computed tomography images of 385 individuals. Nasal floor (NF), medial ethmoid roof point (MERP), cribriform plate (CP) heights, CP depth and width, OF width, lateral lamella-cribriform plate angle (LLCPA), and nasal septum deviation angle (NSDA) were measured. Keros and Gera classifications were made according to the measurements.

Results

According to the Keros classification, 137 of 770 OFs were type I (17.8%), 554 (71.9%) were type II, and 79 (10.3%) were type III. The most common combination was Keros type II and Gera type II (45.6%). There was a positive correlation between CP depth and LLCP angle, NF, MERP and CP heights (P ≤ 0.05). NF, MERP, and CP heights, CP depth and LLCP angle were statistically significant differences according to Keros classification (P ≤ 0.05). Only the right LLCP angle showed a statistically significant difference according to the NSD sides (P = 0.014).

Conclusions

The study shows that the lateral lamella-cribriform plate angle increases as the cribriform plate depth increases. This result suggests that it may moderate the risk during endoscopic sinus surgery. Also, according to the nasal septum deviation sides, the dimensions of the olfactory fossa did not change significantly, except for the lateral lamella-cribriform plate angle.

The Radiological Evaluation of the Crista Galli and Its Clinical Implications for Anterior Skull Base Surgery

INTRODUCTION

Crista galli is extremely important in the endoscopic transcribriform approaches and some extradural approaches. Because of its clinical significance, the morphometric properties of crista galli should be well known. In this study, it was aimed to examine the morphometry and the pneumatization incidence of the crista galli in cone beam computed tomography (CBCT) images.

MATERIAL AND METHODS

In this retrospective study, the length and width of the crista galli were measured in CBCT images of 300 healthy individuals. Besides, the presence of crista galli pneumatization was examined.

RESULTS

The length and width of the crista galli were determined to be as 14.03 ± 2.93 mm and 3.73 ± 1.48 mm, respectively. Pneumatized crista galli was detected in 53 out of 300 individuals (17.67%). There was no statistical difference between the presence of pneumatization and both length and width values of the crista galli (P = 0.876 and P = 0.478, respectively). In addition, no relationship was determined between age and the presence of pneumatization (P = 0.167).

CONCLUSION

In this study, it is seen that the length (range: 6.00-23.40 mm) and width (range: 1.40-8.00 mm) of crista galli are in a very wide range. Besides, it is seen in the literature that the incidence of crista galli pneumatization is in a very wide range (2.4% to 66.6%). Based on the available data, it will not be possible to determine a specific range of values for crista galli morphometry. Therefore, the authors think that CT imaging is extremely important in preoperative evaluation.

Anatomic Variations of Ethmoid Roof and Risk of Skull Base Injury in Endoscopic Sinus Surgery: Statistical Correlations

BACKGROUND

Recent developments in endoscopic sinus surgery (ESS) have increased the need to investigate the complex anatomic variations in the ethmoid roof and skull base, to inform the surgeon about the risk of damaging these crucial areas during ESS.

OBJECTIVE

To offer a detailed description of sinus anatomy focusing on the key surgical landmarks in ESS and frontal recess surgery to standardize a systematic approach during the preoperative sinuses imaging evaluation.Methodology: A total of 220 computed tomography (CT) scans were reviewed to obtain six sets of measurements: the depth of the cribriform plate (CP); the length of the lateral lamella of the cribriform plate (LLCP); the angle formed by the LLCP and the continuation of the horizontal plane passing through the CP; the position of the anterior ethmoidal artery (AEA) at the skull base; the extent of frontal sinus pneumatization (FSP); the type of superior attachment of the uncinate process (SAUP).

RESULTS

The length of the LLCP was statistically significantly correlated with the different Keros classification types, the angle formed by the LLCP with the continuation of the horizontal plane passing through the CP, and with the AEA position at the skull base. The depth of the olfactory fossa was correlated with FSP.

CONCLUSIONS

According to the Keros and Gera classifications, the data obtained from these evaluations allow the assessment of anatomic-radiological risk profiles and can help identify those patients who are high risk for ethmoid roof injury.

Radiological Anatomy of the Olfactory Fossa: Is Skull Base Anatomy Really Ever “Safe”?

Objective Computed tomography (CT) is a powerful tool for delineating the anatomy of the anterior skull base. The goal of this study is to further characterize the relevant anatomical features of this area, along with other parameters important for endoscopic sinus surgery.

Design Retrospective case review.

Setting Tertiary care hospital.

Participants Thirty patients who had CT scans of the paranasal sinuses.

Main Outcome Measures The following features were assessed using image analysis software: olfactory fossa depth, the length and angle of the lateral lamella, fovea ethmoidalis length and shape, ethmoid roof height and slope, and the position and course of the anterior ethmoid artery. Statistical analysis was performed assessing for differences in the above parameters.

Results The mean olfactory fossa depth of the anterior and posterior skull base was 3.4  ± 1.1 and 2.4  ± 0.9 mm, respectively (p < 0.05). The mean lateral lamella length was 3.6  ± 0.9 mm, which did not demonstrate significant variability. The angle of the lateral lamella varied significantly by skull base position, measuring 63.1 ± 17.8 degrees anteriorly, and 39.1 ± 17.9 degrees posteriorly (p < 0.05). In scans classified as a Keros type I, 25.3% had lateral lamellae longer than 4 mm. Furthermore, 43.7% had lateral lamellae with angles less than 45 degrees. Moving anteriorly, the posterior skull base sloped downward in 46.7% of patients.

Conclusion Thorough preoperative assessment of CT scans is crucial to understanding the inherent variability of skull base anatomy. Even “safe” anatomy can still contain features such as long and acutely angled lateral lamella, which may predispose patients to iatrogenic injury.

The Relationship of High Septal Deviation, the Depth of Olfactory Fossa, and Gera Angle: Is High Septal Deviation Associated With Any Anatomic Abnormalities in the Anterior Skull Base?

OBJECTIVE

To investigate the association of high septal deviation with the olfactory fossa depth and Gera angle.

METHODS

Fifty-four computed tomography scans of patients with high septal deviation were evaluated. The olfactory fossa depth and Gera angle were measured. The values of the deviated and nondeviated sides were compared.

RESULTS

No association between high septal deviation and the olfactory fossa depth and Gera angle was found.

CONCLUSION

High septal deviation does not affect the olfactory fossa depth and Gera angle. In other words, the olfactory fossa depth and Gera angle have no association with the high septal deviation.