Olfactory fossa depth: CT analysis of 1200 patients

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.

A Detailed Assessment of Variations of Ethmoid Roof, Olfactory Fossa, and Anterior Ethmoidal Artery on CT Scan of Paranasal Sinuses of 200 Patients

To study and analyse the variations in ethmoid roof anatomy and estimate the anatomical location and variations of AEA on CT scans. The study is conducted on 200 patients for detailed analysis of the olfactory fossa (OF) depth, supraorbital pneumatisation, and AEA location and distance from the skull base. In our study, Keros type II was predominant type seen followed by type I. Asymmetry was noted in 32/200 subjects (16%). The anterior ethmoidal artery (AEA) canal was seen in 341/400 sides (85.2%). We found Keros type II was the most common type in our study. We also found grade I anterior ethmoidal artery as the most common variant and the dangerous grade III anterior ethmoidal artery was least common type found in this study, and there was a significant association of Keros type II with increasing anterior ethmoidal artery grading.

Implications of the olfactory fossa anatomy in intracranial complications of inferomedial orbital decompression

Two patients with thyroid eye disease underwent inferomedial orbital decompression complicated by a cerebrospinal fluid (CSF) leak. One of the cases developed a postoperative pneumocephalus resolved with conservative measures. In the second case, the CSF leak was managed intraoperatively. In both patients, a computed tomography (CT) scan revealed a pronounced slope of the lateral lamella of the cribriform plate, forming an obtuse angle with its lateral bony extension. When this anatomical disposition of the olfactory fossa (OF) is present, the course of the anterior ethmoidal artery (AEA) is usually embedded in the skull base, and its foramen should not be taken as the upper limit of the transconjunctival ethmoidectomy. The shape and relative height of the olfactory fossa and fovea ethmoidalis, and the course of the AEA should always be assessed before transconjunctival medial decompressions.

Examination of ethmoidal roof regarding Keros and Yenigun classifications in a Turkish population: a computerized tomography study

PURPOSE

Understanding ethmoid roof morphology is crucial to prevent complications in endoscopic sinus surgery. This study aimed to evaluate the morphological properties of the ethmoidal roof regarding gender and age differences using Keros and Yenigun classifications on high-resolution computed tomography images.

METHODS

We retrospectively analyzed 891 high-resolution computed tomography paranasal sinus study images and measured the depth of the cribriform plate in coronal sections and the anterior-posterior length in axial planes. The study retrospectively examined CT images of paranasal sinuses of patients living in the eastern Anatolian region of Turkey.

RESULTS

In both Keros and Yenigun Classifications, the most common class was type 2, and the least common class was type 3. According to Keros et al.'s method, no significant difference was observed between men and women (p = 0.698). However, according to Yenigun et al., the average values of women in terms of the anterior-posterior distance of the ethmoid roof were significantly higher than men (p = 0.001). When examined according to age, a very low, negative correlation was revealed regarding Keros and Yenigun classifications (p = 0.047 and p < 0.001 retrospectively). According to Keros and Yenigun's classification, there was no significant difference between the left and right sides (p = 0.488 and p = 0.919, respectively).

CONCLUSION

The morphological properties of the ethmoidal roof have importance to be considered for preoperative planning. Studying larger patient groups and meta-analyses that gather various research results about this subject might help better understand the ethmoidal roof morphology among populations.

Analysis of the Correlation of the Lamina Papyracea-to-Midline Distance with the Location of Anterior Ethmoidal Artery and Keros Classification

The aim of the study was to investigate the relations between anatomical structures that are susceptible to inadvertent injuries during the surgery using preoperative computed tomography (CT) scans. 153 CT scans were reviewed and the distance from the lamina papyracea (LP) to the midline and the distance of the anterior ethmoidal artery (AEA) to the skull base were measured bilaterally. Also, the depth of olfactory fossa was measured and categorized using the Keros classification. The measurements were analyzed to determine whether LP-to-midline distance was correlated with the distance between the AEA and the skull base and Keros classification. Additionally, correlation of Keros classification with the distance from the AEA to the skull base was investigated. In a total of 306 measurements, 26 (%8.49) were classified as Keros type I, 200 (65.35%) as Keros type II and 80 (25.14%) as Keros type III. Statistically, LP-to-midline distances on the right and left sides were significantly associated with the distance from the AEA to the skull base on the same side (R:p < 0.001, L:p = 0.01) and the Keros classification on the same side (R:p < 0.001, L:p = 0.004). Also, a significant association was found between the Keros classification and the distance from the AEA to the skull base (R:p < 0.001, L:p = 0.02). The locations of anatomical structures are defined in relation to each other during the development of maxillofacial bones. CT scans should be examined and anatomical structures and relations among them reviewed very carefully before ESS. Otherwise, some accidental injuries may arise during the surgery while trying to avoid complications.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03931-x.

Computed tomographic assessment of risk of anterior skull base injury of adult patients in tertiary care centre: a cross-sectional study

Background and objectives

Functional endoscopic sinus surgery (FESS) carries the risk of anterior skull base injury. Understanding computed tomography of the paranasal sinuses (CT PNS) and anatomical variations is crucial before surgery. Several classifications, including Kero's, Gera's, and Thailand-Malaysia-Singapore (TMS), assess the risk of skull base injury. The objective was to determine the risk of anterior skull base injury using CT PNS in adult patients.

Methods

A study of 188 patients with head and paranasal sinus pathologies used CT scans to measure olfactory fossa depth, the angle between lamina papyracea and horizontal plane, and the distance from the orbital rim to the cribriform plate. Variations were classified using Kero's, Gera's, and TMS classifications.

Results

The study involved 188 individuals aged 18-85, with OF depths ranging from 0.1 to 0.52 cm. Kero's Class I was observed in 82.44% and 81.38% of individuals, while distances from orbital floor to cribriform plate and ethmoidal roof ranged from 1.37 to 2.93 cm. TMS Type I was observed in all individuals, and the angle between lateral lamella of the cribriform plate and cribriform plate ranged from 34° to 85°. Gera's Class II was observed in 77.12% and 84.57% of individuals.

Conclusion

CT PNS provides important anatomical information for assessing the risk of skull base injury during FESS. Kero's, Gera's, and TMS classifications can be utilized to evaluate this risk. The study findings provide insights into the variations in olfactory fossa depth, distance measurements, and angle, which can aid in preoperative planning and reducing complications during FESS in Nepalese populations.

Anatomy and Pathology of the Skull Base: Malignant and Nonmalignant Lesions

The skull base (SB) is the osseous foundation of the cranial vault. It contains many openings that allow communication between the extracranial and intracranial structures. This communication is crucial in normal physiologic processes yet may also arrow spread of disease. This article provides a comprehensive review of SB anatomy including important landmarks and anatomic variants relevant to SB surgery. We also illustrate the diverse pathologies affecting the SB.

Multidetector CT of the Nasal Cavity and Paranasal Sinuses Variations in 73 Patients

Detailed knowledge of the anatomy of the nasal cavity and paranasal sinuses is very important in the diagnosis of pathological processes, planning of endoscopic surgery, and radiologic guiding techniques during certain operations. Observational study. Clinic of Neurosurgery, Institute and Department of Anatomy and Pathology, Clinic and Department for Otorhinolaryngology and Maxillofacial Surgery, Faculty of Medicine. Two heads with brains were serially cut in the axial and coronal planes. 73 individuals, who were enrolled among 1848 patients, underwent examination by multidetector computerized tomography. A nasal septal deviation was seen in 65.8%, and septal pneumatization in 11%. Superior concha pneumatization was observed in 1.4% of patients, middle concha bullosa in 30.2%, and its hypoplasia in 1.4%. The lamina papyracea dehiscence was also present in 1.4%. The uncinate process was absent in 1.4%, and it was pneumatized in 4.2%. Agger nasi cells were noticed in 34.3%, and Haller and Onodi cells in 20.7% each. The olfactory fossa was shallow in 9.7%, deep in 31.6%, and very deep in 58.9%. Absence of the frontal sinus was seen in 9.7%. The presellar type of the sphenoidal sinus was present in 11%, the sellar in 35.7%, and the postsellar in 53.5%. Hypoplasia of the maxillary sinus was revealed in 1.4%, and hyperpneumatization in 4.2%. The sinus floor was usually below the level (60.3%), at the same level (20.7%), or above the level of the nasal floor (19.2%). The bony septum within the sinus was seen in 52.1%. The presented data are of a great significance in order to avoid a misdiagnosis of the anatomic variations, to make a proper diagnosis of certain diseases, and for safe endonasal operations.

Three-Dimensional Volumetric Analysis of Frontal Ethmoidal Cells and Evaluation of Influential Factors: A Helical Computed Tomography Study

In the present study, we aimed to assess frontal ethmoidal cells by using segmentation 3D software to establish a possible correlation between volume variation and both gender and age, as well as a relationship with Keros classification. Helical computed tomography images were obtained from 71 patients for analysis, in which the agger nasi cell, supra agger cell, supra agger frontal cell, supra bulla frontal cell, supraorbital ethmoidal cell, supra bulla cell, and frontal septal cell were identified and segmented to obtain their volume. Significant differences in volume were found for age and gender regarding agger nasi cells (p-value = 0.017), supra agger cells (p-value < 0.001), and frontal septal cells (p-value = 0.049). In the frontal septal cells, an increase of one year in age reduced the volume by 0.309, on average. According to Keros classification, the mean volumes were 10.07 and 25.64, respectively, for types II and III, both being greater than that of type I. Extracting volumetric data by using segmentation software in agger nasi cells, supra agger cells, and frontal septal cells may be useful for obtaining additional information related to age, in addition to possibly contributing to elucidating the anatomical variations in the region and an identification forensic tool.

CBCT Assessment of Ethmoid Roof Variations through Keros, Gera, and TMS Classifications

Background

This study is designed to assess the variations of the ethmoid roof through the Keros, Gera, and Thailand-Malaysia-Singapore (TMS) classifications by means of Cone-Beam Computed Tomography (CBCT).

Materials and Methods

372 CBCT scans were reviewed. The depth of the olfactory fossa (OF) was defined by the height of the lateral lamella (LL). The degree of the angle formed by the LL and the continuation of the horizontal plane passing through the cribriform plate was calculated. The risk of injury to the skull base was assessed by TMS classification.

Results

The distribution of Keros types 1, 2, and 3 was 20.43%, 66.26%, and 13.31%, respectively. No significant difference was seen in the Keros classification among males and females, and asymmetry in the depth of the cribriform plate was seen in 33.3% of patients. 29.57% of the cases had type I, 61.42% had type II, and 9.01% had type III of Gera classification. 33.9% of the patients had asymmetry in the Gera classification. There was not significant difference in the Gera classification among males and females. 95.43%, 4.17%, and 0.40% of patients were of types 1, 2, and 3 of TMS classification, respectively.

Conclusion

The most prevalent variations of the ethmoid roof were Keros type II, Gera type II, and TMS type 1. Although the prevalence of the dangerous types (Keros type 3, Gera type III, and TMS type 3) was low, preoperative assessment is essential in reducing surgical complications. CBCT is beneficial in evaluating these variations due to its low radiation dose.

A computed tomography study on the olfactory fossa in dried skulls

PURPOSE

The computed tomography (CT) study investigates the olfactory fossa (OF) morphometry and morphology.

METHODS

Fifty Greek adult dried skulls were macroscopically investigated for the detection of the OF morphological patterns and after a multiplanar CT reconstruction, the OF morphometry was accurately calculated using a digital ruler.

RESULTS

Types I and II surface contour patterns were the most frequently identified (36 and 32%), followed by types III, IV, and V (16, 12, and 4%). Crista galli mean length, height, and width were 19.46 ± 2.34 mm, 12.69 ± 2.7 mm, and 5.18 ± 1.11 mm. The OF mean maximum length was 22.29 ± 2.16 mm on the right and 22.10 ± 2.44 mm on the left side, and symmetry was detected. The OF median values of the maximum depth for its anterior, middle, and posterior third were 4.91 mm, 4.72 mm, and 2.78 mm on the right and 4.55 mm, 4.75 mm, and 2.55 mm on the left side. Symmetry was observed in any third of the OF. The OF median values of the surface maximum width for the anterior, middle, and posterior thirds were 9.29 mm, 11.48 mm, and 13.07 mm. A significant gradual increase of the OF surface maximum width was detected in the anteroposterior direction in the total sample (p < 0.001), with the highest value (23.12 mm) in the posterior third. A significant (p < 0.001) very strong (r_s = -0.798) and a moderate (r_s = -0.524) negative linear correlation in the OF anterior and middle third were, respectively, identified between its maximum depth and width. No gender impact was identified.

CONCLUSIONS

The study helps to familiarize with the calculation of the OF dimensions and simplifies the understanding of its complex anatomy, to reach successful surgical planning and minimize perioperative complications.

Patterns of Pneumatization of the Posterior Nasal Roof

(1) Background: For good surgical performance, sound knowledge of anatomy is required. Although the ethmoid air cells and sphenoid sinuses are subject to a high degree of variation, their possible extensions above the nasal fossa at the posterior end of the cribriform plate of the ethmoid bone (CPEB) were seemingly overlooked. (2) Methods: We retrospectively studied 162 case files from 55 male and 107 female cases, with ages varying from 42 to 80, which were scanned using Cone Beam Computed Tomography. (3) Results: In 56.17% of cases, an unpneumatized CPEB (type I) was found. Nasal roof recesses of ethmoidal origin (type II) were found at the posterior end of the CPEB in 20.37% of cases. Different types of sphenoidal pneumatizations of the posterior end of the CPEB (type III) were found in 22.83% of the cases. Onodi cells projected nasal roof recesses (type IV) in only 10 cases. In all types, nasal roof recesses were found either above the CPEB or within/underneath it. Moreover, such nasal roof recesses were found to be either unilateral, extended contralaterally, or bilateral. (4) Conclusions: As such recesses of the posterior CPEB, previously overlooked, belong to the posterior rhinobase, they should be carefully documented preoperatively to avoid unwanted surgical damage to the olfactory bulb or CSF fistula.

The Relation Between the Metopic Suture Persistence and Frontal Sinus Volume and Olfactory Fossa Depth: A Reliability Study with Semiautomatic Volume Measurement

Objective:

This study aims to investigate the relationship of the persistence of metopic suture (PMS), frontal sinus volume (FSV), and olfactory fossa depth (OFD).

Methods:

Tomography scans of 1,603 patients aged 18-65 years were evaluated for the presence of PMS. In the study, 74 PMS cases and 74 controls were included. The appearance of each individual’s frontal sinus was classified as aplasia, hypoplasia, or normal. Two observers independently measured the lateral lamella length (LLL), OFD, and FSV. Interobserver agreement was evaluated with the intraclass correlation coefficient (ICC) and Cohen’s kappa coefficient (κ).

Results:

The prevalence of PMS was found to be 4.99% [95% confidence interval (CI): 4.03-6.17]. The PMS group had five times higher hypoplasia/aplasia than the controls (52.70%, 95% CI: 41.48-63.66 and 10.81%, 95% CI: 5.58-19.91, respectively; p<0.001). An “almost perfect” agreement was detected among observers for the frontal sinus appearance classification: κ=0.807, p<0.001. The ICC of continuous measurements for OFD, LLL, and FSV, respectively, presented “excellent” reliability: 0.956, 0.958, and 0.981, with p<0.001 for each. LLL was shorter, OFD was shallower, and FSV was smaller in the PMS group than the control group (p<0.001). There was a moderate positive correlation between OFD, LLL, and FSV (r=0.306, r=0.302).

Conclusions:

This study interprets that the presence of PMS is related frontal sinus development and volume. With PMS, a smaller FS, shorter lateral lamella, and shallower olfactory fossa may be expected.

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.

Ambiguous "olfactory" terms for anatomic spaces adjacent to the cribriform plate: A publication database analysis and quest for uniformity

A precise nomenclature and terminology is the foundation of communication in Anatomy and related biomedical sciences. The olfactory bulbs and nerves lie above and below the cribriform plate (CP), respectively. Hence, many anatomical landmarks in this region have names adopting the term "olfactory" as qualifiers. Ambiguous use of these "olfactory" terms exists, with some potential repercussions on patient treatments. We performed a publication database analysis to determine the frequency of misuse of names for seven anatomical "olfactory" spaces close to the CP and nasal cavity. We searched PubMed® publications having the keyword "olfactory" in their title or abstract, plus one of seven other keywords: "groove", "fossa", "recess", "cleft", "vestibule", "sulcus", and "cistern". We reviewed all abstracts for accuracy of these terms relative to accepted norms or customary definitions. By February 2020, we found all these keywords in 1255 articles. For the terms olfactory "groove" and "fossa", the number of relevant articles (and percentage of those inaccurately using these terms) were 374 (1.1%), and 49 (8.2%), respectively. All 52 abstracts containing "olfactory" and "vestibule" were irrelevant, relating to the "nasal vestibule" and olfactory function, instead of "olfactory vestibule". Overall, terms used to describe "olfactory" spaces near the CP are seldom ambiguous or inaccurate, but the terms olfactory "groove" and "fossa" are occasionally misused, We propose several new "olfactory" terms for inclusion in the Terminologia Anatomica, and stress the need for uniform nomenclature leading to greater consistency and accuracy in clinical use of anatomical terms containing the word "olfactory" as a descriptor.

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.

The Risks of Complications During Endoscopic Sinus Surgery in Cystic Fibrosis Patients: An Anatomical and Endoscopic Study

OBJECTIVE/HYPOTHESIS

An increasing proportion of adult cystic fibrosis (CF) patients is being referred to endoscopic sinus surgery (ESS) in order to relieve the symptoms of chronic rhinosinusitis (CRS). Given that CFTR mutations profoundly alter sinonasal development, we want to explore the relationship between their peculiar surgical anatomy and the risk of postoperative complications.

STUDY DESIGN

Retrospective case-control study.

METHODS

Paranasal sinuses CT scans of 103 CF adult patients with CRS were compared to those belonging to a cohort of 100 non-CF adult patients to explore their anatomical differences. Secondly, CF and non-CF patients who received primary/revision ESS were analyzed in order to assess their preoperative CT scan in terms of surgically relevant variants, and according to the CLOSE checklist. Surgical outcomes were statistically compared in order to explore the differences between groups.

RESULTS

CF group presented more frequently with smaller and less pneumatized paranasal sinuses and a higher Lund-Mckay score compared with controls. No anatomical differences emerged in terms of genotype stratification. Non-CF CRS patients undergoing ESS showed a significantly deeper olfactory fossa and a more frequent supraorbital pneumatization compared to CF patients (P < .001 and P = .031, respectively). Whereas this latter group underwent more often aggressive surgical procedures (P = .001), no difference in terms of postoperative adverse events was found (P = .620).

CONCLUSIONS

Despite receiving more often aggressive ESS procedures, adult CF patients do not show an increased risk of postoperative complication and this may be linked to a different proportion of anatomical and surgically-relevant variants.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E2481-E2489, 2021.

Adult and Pediatric Lateral Lamella Cribriform Plate Height: In Need for a Comparative Study

Surgery for sinuses has evolved with the advancement of instruments and modification in techniques. Endoscopes have expanded the surgical roles for lesions in the nose and para-nasal sinuses with reduced rate of complications and cosmetic side effects. Nevertheless sinus surgery in pediatrics patients has its own challenges. Pre-operative imaging is of paramount important especially when embarking on skull base procedures. The differences between adult and pediatric anatomy need to be further studied.