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.

Risk Factors for Anterior Skull Base Injury in Endoscopic Sinus Surgery

Objectives This retrospective study aimed to investigate the relationships between the Keros classification, the Gera classification, the vertical height of the posterior ethmoid roof (ER), and anterior ethmoidal artery (AEA) types in Japanese patients. Methods We investigated the computed tomography (CT) slices of paranasal sinuses (120 sides) of 60 patients; measured the cribriform plate (CP) depth, lateral lamella CP angle (LLCPA), and vertical height of the lateral ER from the hard palate (LERHP) at the coronal plane of the posterior ethmoidal artery (PEA); and reviewed the AEA types, whether floating or non-floating. Results CP depth was positively correlated with LLCPA (r=0.63; p<0.01) and the height of LERHP (r=0.19; p<0.05). The height of the LERHP in females was significantly lower than that in males. With increased CP depth, floating AEAs became prevalent (p<0.001). Conclusion In females, low height of the posterior ethmoid sinus roof, where cerebrospinal fluid (CSF) leaks occurred while penetrating the basal lamella, often existed; the heights positively correlated with the Keros classification in Japanese patients. The Keros and Gera classifications, AEA type, and posterior ER height do not individually constitute a complete risk assessment but may correlate, preventing major complications, such as CSF leak and orbital hemorrhage.

Review of olfactory cleft roof anatomy

Progress in skull-base endoscopic surgery has improved our knowledge of olfactory cleft (OC) anatomy. This article presents a review of current knowledge concerning the OC roof: descriptive anatomy, radiological exploration, and endoscopic observation. The OC is a narrow area in the most superior part of the nasal cavity. Its roof is the thinnest structure separating the nasal cavities from the brain; it comprises three superimposed tissues: nasal mucosa, ethmoid cribriform plate (ECP), and dura mater. The ECP comprises the anterior ECP containing the ethmoidal slit (ES) medially and the cribroethmoidal foramen (CEF) laterally; and the posterior ECP, comprising the olfactory foramina. The OC roof is bordered anteriorly by the nasal bone roof, laterally by the lateral ethmoid masses, and posteriorly by the jugum and anterior wall of the sphenoid sinuses. Imaging is crucial for analyzing this wall, providing precise detailed information on conformation and anatomic relations with adjacent structures such as the anterior ethmoidal artery. Understanding OC roof anatomy and correct interpretation of imaging are essential for safety in present-day functional endoscopic sinus surgery and anterior skull-base oncologic surgery.

Anterior Skull Base Abnormalities in Congenital Anosmia

INTRODUCTION

The structures of the skull and the brain are related to each other. Prior work in individuals with isolated congenital anosmia (ICA) showed that these individuals were characterized by olfactory bulb (OB) defects. The aim of this study was to compare the morphological pattern of the anterior skull base surrounding the OB between individuals with ICA and normosmic controls. We meant to investigate whether these features can help distinguish abnormalities from normal variation.

METHODS

We conducted a retrospective study to acquire T2-weighted magnetic resonance images from individuals diagnosed with ICA (n = 31) and healthy, normosmic controls matched for age and gender (n = 62). Between both groups, we compared the depth and width of the olfactory fossa, the angle of the ethmoidal fovea, as well as the angle of the lateral lamella of the cribriform plate. Within the ICA group, we further performed subgroup analyses based on the presence or absence of the OB, to investigate whether the morphology of the anterior skull base relates to the presence of OBs. The diagnostic performance of these parameters was evaluated using receiver operating characteristic analysis.

RESULTS

Individuals with ICA exhibited a flattened ethmoid roof and shallower olfactory fossa when compared to controls. Further, the absence of the OB was found to be associated with a higher degree of flattening of the ethmoid roof and a shallow olfactory fossa. We reached the results in the following areas under the receiver operating characteristic curves: 0.80 - angle of fovea ethmoidalis, 0.76 - depth of olfactory fossa, 0.70 - angle of lateral lamella of the cribriform plate for significant differentiation between individuals with ICA and normosmic controls.

CONCLUSION

Individuals with ICA exhibited an unusual anterior skull base surrounding the OB. This study supports the idea of an integrated development of OB and anterior skull base. Hence, the morphological pattern of the anterior skull base surrounding the OB helps distinguish individuals with ICA from normosmic controls and may therefore be useful for the diagnosis of ICA, although it is certainly not an invariable sign of congenital anosmia.

Management of Traumatic and Non-Traumatic Cerebrospinal Fluid Rhinorrhea-Experience from Three Southeast Asian Countries

BACKGROUND

Cerebrospinal fluid (CSF) rhinorrhea requires proper management to avoid disastrous consequences. The objectives of this study were to ascertain the patient characteristics, etiologies, sites of defect, skull base configurations, methods of investigation, and management outcomes of CSF rhinorrhea.

METHODS

A retrospective study was performed over 4 years involving three surgeons from Malaysia, Singapore, and Thailand. Hospital records were reviewed to determine the patients' characteristics, the causes and sites of leaks, methods of investigation, skull base configurations, choices of treatment, and outcomes.

RESULTS

A total of 15 cases (7 traumatic and 8 non-traumatic) were included. Imaging was performed in all cases. The most common site of leakage was the cribriform plate (9/15 cases). The mean ± SD of the Keros heights were 4.43 ± 1.66 (right) and 4.21 ± 1.76 mm (left). Type II Keros was the most common (60%). The mean ± SD angles of the cribriform plate slope were 51.91 ± 13.43 degrees (right) and 63.54 ± 12.64 degrees (left). A class II Gera configuration was the most common (80%). All except two patients were treated with endonasal endoscopic surgical repair, with a success rate of 92.3%. A multilayered repair technique was used in all patients except one. The mean ± SD postoperative hospital stay was 9.07 ± 6.17 days.

CONCLUSIONS

Non-traumatic CSF rhinorrhea outnumbered traumatic CSF rhinorrhea, with the most common site of leak at the cribriform plate. Imaging plays an important role in investigation, and Gera classification appears to be better than Keros classification for evaluating risk. Both conservative and surgical repairs are practiced with successful outcomes. Endonasal endoscopic CSF leak repair is the mainstay treatment.

Olfactory Fossa Evaluation as a Maxillary Sinus Development Using Cone Beam Computed Tomography

In our study, we aimed to evaluate the risk of skull base perforation during endoscopic sinus surgery in individuals with hypoplasic maxillary sinuses using Cone Beam Computed Tomography (CBCT). We included 52 patients with bilateral maxillary sinus hypoplasia and 52 patients with normal maxillary sinus in the study. Reviewing paranasal CBCT scans, we noted the olfactory fossa depths and lateral lamella lengths of all the groups and compared between the hypoplasia groups and the control group. Compared the maxillary hypoplasia sinus individuals with the control group, both the olfactory fossa depths and the lateral lamina length were different in the maxillary hypoplasic individuals. In individuals with hypoplasic maxillary sinus, the olfactory fossa depth and the lateral lamina length values are higher, which increases the risk of complications in endoscopic sinus surgery.

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.

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.

Lateral Lamella of Cribriform Plate (LLCP): A Computed Tomography Radiological Analysis

Spectrum of disease involves nasal passage and paranasal sinuses termed as sinonasal disease. CT is superior to other imaging modalities in the assessment of the paranasal sinuses (PNS) pathology. Functional Endoscopic Sinus Surgery (FESS) is the common modality of treatment for diseases of nose and PNS. Coronal CT images closely correlates with the surgical approach. Therefore, CT is the preferred study before FESS. The lateral lamella of cribriform plate (LLCP) is the thinnest bone in the anterior skull base and most vulnerable parts of the skull base for iatrogenic complication during FESS. Therefore, preoperative evaluation of LLCP is importance in a successful FESS. The study focused on the vertical height of the LLCP and the angulation of LLCP with CP. This study was performed retrospectively on CT images of 600 adult subjects. Chi square test and pearson correlation were used for data analysis. Type II is most prevalent type of Kero's type. There is a significant correlation between Kero's classification and Gera's classification. A positive correlation found between the vertical height of LLCP with its angle formed by CP and the correlation was found to be significant. Assessment on LLCP in its 2 aspect both vertical height of LLCP and its sloping with CP certainly gives a map to the surgeon during FESS and to improve the safety profile of the procedure.

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.

Anterior and Central Skull Base Tumors: Key Points for the Radiologist to Analyze Prior to Endoscopic Approaches

Initially developed as a minimally invasive technique to approach inflammatory conditions, transnasal endoscopic surgery has progressively expanded its anatomic targets and clinical indications. Consequently, numerous surgical approaches to the anterior and central skull base were developed, referred to as extended endonasal approaches (EEA). The intrinsic advantage of EEA is the exploitation of a natural corridor provided by sinonasal airspaces, with no need for skin incision and osteotomy and limited soft tissue damage. In this context, imaging plays essential role, demonstrating the relevant anatomic relationships of the lesion, the proper surgical corridor, the anatomic variants that may increase the surgical risk.

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 Importance of Cribriform-Lamella Angle in Endoscopic Sinus Surgery

The aim of this study is to evaluate cribriform-lamella (CL) angle and length of lateral lamella (LL) on CT scan and to correlate CL angle with LL length and Keros classification. Retrospective study analyzing 500 CT scans of PNS was performed at a tertiary care hospital. The CT scan anatomy of anterior cranial base was evaluated for Keros, CL angle and LL length. The relationship between these measurements was studied. Keros type I (75.2%) was the commonest finding in our study. Males have increased depth of olfactory fossa but there were no differences between the sides. Type A angle of CL (66.1%) was the commonest with females having an increased CL angle as compared to males. The LL length was 3.6 mm (± 0.8). There were no significant difference between sex/side of LL. Keros was found to be strongly correlated with the LL length whereas it has mild negative correlation with CL angle. There was no correlation between CL angle and LL length. Keros classification is the commonest criteria used to assess the risk of injury to anterior cranial base. However, we have found that the CL angle has an important role to play in the angulation/slope/level of anterior cranial base during endoscopic sinus surgery. CL angle needs to be considered as an important factor during endoscopic sinus surgery.

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.

A new radiological classification for the risk assessment of anterior skull base injury in endoscopic sinus surgery

Keros and Gera classifications are widely used to assess the risk of skull base injury during endoscopic sinus surgery. Although, both classifications are useful preoperatively to stratify risk of patients going for surgery, it is not practical to measure the respective lengths during surgery. In this study, we aimed to propose a new radiological classification (Thailand-Malaysia-Singapore (TMS)) to assess the anatomical risk of anterior skull base injury using the orbital floor (OF) as a reference. A total of 150 computed tomography images of paranasal sinuses (300 sides) were reviewed. The TMS classification was categorized into 3 types by measuring OF to cribriform plate and OF to ethmoid roof. Most patients were classified as TMS type 1, Keros type 2 and Gera class II, followed by patients classified as TMS type 3, Keros type 1 and Gera class 1. TMS has significant correlation with Keros classification (p < 0.05). There was no significant correlation between Keros and Gera classifications (p = 0.33) and between TMS and Gera classifications (p = 0.80). The TMS classification has potential to be used for risk assessment of skull base injury among patients undergoing ESS. It serves as an additional assessment besides the Keros and Gera classifications.

Double-blind, randomised controlled trial on the efficacy of saline nasal irrigation with sodium hyaluronate after endoscopic sinus surgery

Objective

There is a growing interest in sodium hyaluronate for the clinical management of patients who undergo functional endoscopic sinus surgery for chronic rhinosinusitis, because of the mucosal regenerative properties of this macromolecule. However, its role in post-operative care is still debated. This study aimed to evaluate the effect of sodium hyaluronate administered via nasal irrigation with saline, in the post-operative period, after functional endoscopic sinus surgery.

Methods

A multicentric, prospective, randomised, double-blind, parallel group study was conducted on 56 consecutive patients who underwent functional endoscopic sinus surgery for chronic rhinosinusitis without polyps. Group 1 received the standard therapy of normal saline; group 2 received saline plus sodium hyaluronate.

Results

Both objective and subjective measurements, in terms of endoscopic appearance and patient-reported satisfaction, were significantly better in group 2 compared to group 1.

Conclusion

Sodium hyaluronate may be a useful adjunct to nasal saline irrigation in the early post-operative period following functional endoscopic sinus surgery.