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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.

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PURPOSE: To review the literature on the location of the anterior ethmoidal foramen (AEF) and trauma during transconjunctival medial wall decompression. METHODS: A comprehensive literature search was conducted using the PubMed, Embase, and Scopus databases, combining the terms "olfactory fossa" and "fovea ethmoidalis" with "trauma," "cerebrospinal fluid leak," "pneumocephalus," "orbital decompression," and "anterior ethmoidal artery" (AEA). All cases of cranial base trauma during medial orbital decompression and the anatomical studies on the location of the AEF and the course of the AEA were reviewed. RESULTS: Ninety-four articles were identified, of which 37 were related to the AEF, 41 reported the course of the AEA, and 16 to reported cases of cranial base trauma. Out of these cases, 10 were related to transconjunctival medial orbital decompression, affecting 11 patients. Most AEFs are situated at the frontoethmoidal suture, but up to 38.15% of AEFs are located above the suture on the frontal bone. Most AEFs are adjacent to the roof of the ethmoidal sinus. The distance of the AEF to the cranial base increases in the presence of supraorbital ethmoidal cells (SOEC). CONCLUSIONS: The position of the AEF is variable and should not be considered a safe landmark for all patients.

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This study aimed to investigate the olfactory fossa anatomy (Keros types) and its relationship with changes in adjacent anatomical structures using cone-beam computed tomography (CBCT). In this descriptive-analytical study, the paranasal CBCT of 120 healthy adults over 18 years of age were evaluated. The olfactory fossa depth on both sides and the degree of asymmetry on both sides were reported. Correlation of olfactory fossa depth with the size of adjacent anatomical structures such as middle concha length, maximum orbital height and distance from ethmoid roof to nasal floor and ethmoid roof height to the palate in the anterior and posterior, length, and lateral angle of the lamella and cribriform plate distance. The lower concha junction was examined. The most common olfactory fossae on both sides of the Keros classification were Type II, Type I, and Type III, respectively. The mean dimensions of adjacent anatomical structures on the right and left did not differ significantly. The length and lateral angle of the lamella and the height of the ethmoid roof to the floor of the nose, and the height of the ethmoid roof to the palate in the back, on the right, and left in Type III were greater. The lateral angle of the left lamella was greater in Type III. The relationship between olfactory fossa depth and changes in anatomical structures were not significantly correlated with increasing olfactory fossa depth. Supplementary Information: The online version contains supplementary material available at 10.1007/s12070-023-03538-2.

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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 This study is designed as retrospective analysis. Setting The study setting comprises of tertiary academic medical center. Participants In total, 506 patients aged 0 to 18 who had undergone maxillofacial and or head CTs between 2009 to 2016 were involved. 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 three age groups adjusting for sex. Analysis of covariance (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 were 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.

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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.

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BACKGROUND: The morphology of crista galli (CG) varies from one individual to another and its structure may be pneumatized or compact bone. This study purposed to investigate the morphometry of the CG on cone-beam computed tomography (CBCT) scans, to apply morphological classification based on the characteristics of the CG morphometry and to analyse the association of morphological and morphometric features with sex. MATERIALS AND METHODS: The width, length, and height of the CG were calculated on the CBCT scans of 400 patients (233 females, 167 males). The CG was categorised into three morphological types and the presence of the CG pneumatization and the Keros classification were examined. RESULTS: The average length of the CG was 12.93 ± 2.12 mm, the average width of CG was 4.79 ± 1.54 mm, and the average height of CG was 16.21 ± 2.73. There was no statistical difference between sexes in both height and length values. The mean CG width of female patients was found to be statistically significantly higher than that of male patients. No statistically significant difference was determined between the morphological types of CG and sex. For width only, the area under the receiver-operating characteristic curve was found to be significantly higher than 0.5 and the cutoff value for the width parameter was determined as 4 mm. CONCLUSIONS: The morphologic and morphometric features of CG, presence of pneumatization and relation of the anatomy of olfactory region to CG can be analysed in detail using CBCT. The mean CG width of female patients was found significantly higher than that of male patients. However, further studies with different populations and modalities are needed to evaluate the relationship between morphologic and morphometric features of CG and sex.

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Background Clinical hyposmia and anosmia are commonly seen, most frequently with either post-inflammatory, age-related, or idiopathic causes being most frequent. Actual anatomical abnormalities of the olfactory groove or olfactory bulb are far less common. A recent case report showing a possible link between congenital olfactory bulb agenesis and Wolff-Parkinson-White syndrome suggested that there may be a relationship between cardiac arrhythmia and olfactory bulb development. While Kallmann syndrome (KS) is the classic syndrome involving olfactory bulb agenesis and hypogonadotropic hypogonadism, this case report and a prior report noting isolated hypogonadotropic hypogonadism and the Wolff-Parkinson-White syndrome suggest there may be more rare associations between cardiac arrhythmia and olfactory groove abnormalities. Methods A retrospective study was conducted to attempt to elucidate whether there may be a link between cardiac arrhythmias and olfactory anatomical abnormalities. The olfactory bulb volume (OBV) and olfactory sulcus depth (OSD) of 44 patients with cardiac arrhythmias were compared to 43 healthy control patients. Additionally, 11 patients with acute COVID-19 were also compared in those groups. Patients were seen between September and December 2020. Available MRI images were utilized. Results The average right and left olfactory bulb volume was 29.42±18.17 mm3 and 25.67±15.29 mm3 for patients with cardiac arrhythmia, 40.79±30.65 mm3 and 38.95±21.87mm3 for healthy controls, and 21.30±15.23 mm3 and 17.75±9.63 mm3 for COVID-19 patients. The average right and left olfactory sulcus depth was 7.68±1.31 mm and 7.47±1.56 mm for patients with cardiac arrhythmia, 10.67±1.53 mm and 10.62±1.67 mm for controls, and 7.91±0.99 mm and 8.02±0.88 mm for COVID-19 patients. The right and left olfactory bulb volume difference versus controls was significant for cardiac arrhythmia patients (p=0.028 and p=0.0038) and for COVID-19 patients (p=0.047 and p=0.0029), and the right and left olfactory sulcus depth difference versus controls was significant for cardiac arrhythmia patients (p<0.0001 and p<0.0001) and for COVID-19 patients (p<0.0001 and p<0.0001). Both COVID-19 and cardiac arrhythmia patients were, on average, significantly older than controls. On multivariate analysis, cardiac arrhythmia or COVID-19 diagnosis did not significantly correlate with smaller olfactory bulb volume, but older age, cardiac arrhythmia diagnosis, and COVID-19 diagnosis did significantly correlate with smaller olfactory sulcus depth. On multivariate analysis, older age was significantly correlated with cardiac arrhythmia diagnosis and COVID-19 diagnosis. Conclusions Olfactory bulb volume and olfactory sulcus depth in both cardiac arrhythmia and COVID-19 patients appeared significantly smaller than in controls. Cardiac arrhythmia and COVID-19 patients were significantly older than controls. Age, as well as genetic predisposition, may contribute to a difference in the radiographic olfactory anatomical findings in patients with cardiac arrhythmias and COVID-19.

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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.

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BACKGROUND: Olfactory nerve schwannomas are extremely rare. Their origin is still unclear, since olfactory nerve has no Schwann cells. There are about 70 case reports of olfactory nerve schwannoma in the world literature. Original articles devoted to this issue are currently absent. RESULTS: We present a 55-year-old patient with olfactory nerve schwannoma who underwent surgery at the Federal Center of Neurosurgery in Novosibirsk. MRI revealed extracerebral mass lesion of anterior cranial fossa base with left-sided lateralization resembling meningioma of the olfactory fossa. The patient underwent microsurgical resection of mass lesion of anterior cranial fossa base through left-sided lateral supraorbital craniotomy. The tumor macroscopically resembled schwannoma. Total resection was carried out. Considering morphological structure and immunomorphological characteristics, we verified schwannoma Grade 1. CONCLUSION: Olfactory nerve schwannomas are rare tumors with benign histological structure. Relapses after total resection are unlikely. However, further research of this rare pathology and long-term postoperative follow-up are required.

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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 (rs = -0.798) and a moderate (rs = -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.

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Objective Endoscopic sinus surgery (ESS) is now the most often utilized surgical procedure for treating chronic sinonasal disorders. Therefore, anatomical knowledge of its variations is required to avoid serious postoperative complications. Thus, careful preoperative examination for patients with a paranasal sinus CT scan is necessary. Our study aims to evaluate Keros types and their incidence by evaluating the olfactory fossa (OF) depth according to the Keros classification on paranasal sinus CT scans in the Qassim region. Methods A cross-sectional study was conducted between January 2018 and January 2021 on 148 patients with an average age of 32.59 ± 6.1 who had a non-enhanced paranasal sinus CT scan evaluated by a consultant radiologist using the PACS (picture archiving and communication system) software. Statistical analysis was performed using the statistical software package SPSS version 25 (IBM Corp., Armonk, NY). The chi-square test was used to analyze the relationship between findings and patient characteristics. Also, a p-value of < 0.05 was kept in mind to indicate statistical significance. Results The average depth of the right olfactory fossa (OF) was 5.1 mm with a standard deviation of 1.756 while it was 5.28 on the left side with a standard deviation of 1.66. According to the Keros classification, out of a total of 296 OF, type 1 was found in 84 (28.4%), type 2 in 188 (63.5%), and type 3 in 24 (8.1%). Consequently, the majority of cases were of type 2. Also, we found that type 2 was the most common on both sides in males, whereas, in females, type 2 was the most common on the left side and type 1 on the right side. Conclusion The study of the Keros classification is significantly important to evaluate the anatomy of the anterior skull base and give the surgeon knowledge about the depth of the olfactory fossa. Thus, a preoperative CT scan of the paranasal sinus is critical to ensure that the surgical approach is properly planned and possible surgical complications related to the anatomy of this area can be prevented. Our study showed that Keros type II is the most common, followed by type I and then type III.

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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.

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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.

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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.

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OBJECTIVES: To investigate the olfactory fossa depths and lateral lamella lengths of patients with different types of developmental disorders of paranasal sinuses in comparison with normal controls. STUDY DESIGN: Retrospective, archival, radio-anatomical study. METHODS: We included 58 patients with maxillary sinus hypoplasia, 50 patients with frontal sinus hypoplasia/aplasia, 50 patients with sphenoid sinus hypoplasia/aplasia, and 40 normal controls. Reviewing paranasal computerized tomography 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. RESULTS: Compared with the normal controls, the maxillary hypoplasia group (P < 0.001), frontal hypoplasia/aplasia group (P = 0.004), and sphenoid hypoplasia/aplasia group had significantly deeper olfactory fossa (P = 0.003). The mean lateral lamella lengths in the type 1, type 2, and type 3 hypoplastic maxillary sinus groups were significantly greater compared with that in the control group (P < 0.001). Additionally, the mean lateral lamella lengths in the hypoplastic frontal sinus, aplastic frontal sinus, and hypoplastic sphenoid sinus groups were significantly greater compared with that in the control group (P < 0.001). CONCLUSION: The patients with pneumatization defects of the maxillary, frontal, and sphenoid sinuses had deeper olfactory fossa and longer lateral lamella related to increased risk of skull base injury during endoscopic sinus surgery. LEVEL OF EVIDENCE: 3 Laryngoscope, 129:2458-2463, 2019.

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OBJECTIVES: In the present study, we investigated the relationship between olfactory fossa, cribriform plate, crista galli and nasal Septal Deviation (SD). Keros classification of olfactory fossa was also performed. METHODS: This study was performed retrospectively. Computerized Tomography (CT) images of 200 adult subjects were observed. Unilateral nasal Septal Deviation (SD) cases were included into the study. On coronal CT scans, SD side and location, SD angle, cribriform plate width, olfactory fossa depth (Keros classification) and width, area of the olfactory fossa, crista galli length, width and pneumatization were evaluated. RESULTS: Anterior and anteroposterior deviations were detected mainly. In females, 64.0% and in males, 45.3% of the SDs were located anteriorly. In males, anteroposterior SDs (40.0%) were detected more than females. In anteroposterior SDs, SD angle was higher than anterior SDs. With higher SD angle, crista galli width and height decreased. Cribriform plate width, olfactory fossa height, width and area values of contralateral side were significantly higher than those of the ipsilateral side. For Keros classification, in male group, type 1 (53.3%) and in females, type 2 (57.6%) was detected at ipsilateral side. For contralateral side, type 2 Keros was detected in both genders. Complete crista galli pneumatization was observed in 4.0% and partial pneumatization was detected in 12.0%. In 84% of the patients, there is no Crista galli pneumatization. With the presence of pneumatized crista galli, contralateral Keros values decreased. Crista galli height and contralateral olfactory fossa width showed positive correlation. In older patients, cribriform plate width decreased. CONCLUSION: In our study, there was no Keros type 3 olfactory fossa. In males' contralateral side of SD; and in females both ipsilateral and contralateral side of SD, Keros type 2 olfactory fossa were detected. Therefore, during sinus surgery, surgeons should work carefully not to made intracranial penetration.

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OBJECTIVE: All successful endonasal surgery, including functional endoscopic sinus surgery (FESS), depends on knowledge of both anatomy and the specific variations that can occur between and within patients. Familiarity with these structures is a critical component in preventing complications from these procedures, and failure to understand subtle variation can have disastrous results. The aim of this study was to characterize the anatomical variations (if any) of the cribriform plate using a large cadaveric sample set. Better understanding of the disparities within and between patients may have important implications for surgical planning. METHODS: Whole human skull specimens (31 specimens, 62 sides) were examined to obtain dimensional measurements of the cribriform plate on the right and left sides. RESULTS: The average length of the cribriform plate was 21.28mm (range 15.25-27.73mm, SD 3.30mm). The average width of the cribriform plate (including the crista galli) was 4.53mm (range 1.75-8.03mm, SD 1.20mm). When comparing side differences in individual specimens, there was more variability between widths, relative standard deviation 26.4%, than between lengths, relative standard deviation 15.5%. CONCLUSION: There is a range of both length and width of the cribriform plate, between and within individuals. This is particularly true for width. In practice, this emphasizes the importance of pre-operative imaging and recognition of anatomic variability for sinus or anterior skull base procedure.

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BACKGROUND: Olfactory fossa (OF) is a depression in anterior cranial cavity whose floor is formed by cribriform plate of ethmoid. Lateral lamella, which forms its lateral boundary, is a thin plate of bone and is at risk of injury during functional endoscopic sinus surgery, especially when fossa is deep/asymmetric. AIMS: To measure the variations in the depth of OF and categorize Kerala population as per Keros classification using computed tomography (CT). SETTINGS AND DESIGN: This study was conducted in our institution from January 2016 to August 2017. Patients >16 years of age undergoing CT scan of paranasal sinuses (PNS) were included. MATERIALS AND METHODS: Coronal PNS CT scan studies of 1200 patients were reviewed. The depth of OF was measured from vertical height of lateral lamella. STATISTICAL METHODS: Results were analyzed according to gender and laterality using independent sample t-test and Chi-square test. RESULTS: The mean depth of OF was 5.26 ± 1.69 mm. Statistically significant difference was seen in the mean depth of OF between males and females but not between right and left sides. Keros type I was found on 420 sides (17.5%), type II in 1790 (74.6%), and type III on 190 sides (7.9%). Type III Keros was more on the right (9%) than left (6.8%) side, more in males (9.5%) than females (5.9%), and more among males on the right side (11.4%). Asymmetry in OF depth between two sides was seen in 75% of subjects. CONCLUSION: Prevalence of the dangerous type III OF, even though low, is significant especially among males and on the right side. Therefore, preoperative assessment of OF depth must be done to reduce iatrogenic complications.

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BACKGROUND/AIMS: Spontaneous cerebrospinal fluid (SCSF) leaks are associated with a high body mass index (BMI) and an expanded skull base. The purpose of this study is to determine if a correlation exists between BMI and olfactory fossa depth (OFD) in patients with SCSF leaks and those without. METHODS: This is a cross-sectional study evaluating the correlation between OFD and BMI in patients with and without SCSF leaks. OFD was measured on computed tomography obtained in temporal proximity to the BMI. RESULTS: Patients with SCSF leaks had a deeper mean OFD than controls (6.39 vs. 5.46 mm, p = 0.013) and a larger BMI (38.2 vs. 30.5, p = 0.0003). Pearson correlation was positive between BMI and OFD in women from the control group (R = 0.319, n = 93, p = 0.002 on the left; R = 0.313, n = 93, p = 0.002 on the right) but insignificant in men. CONCLUSIONS: The olfactory fossa is deeper and the BMI higher in patients with SCSF leaks than in those without. Differences were statistically significant. Higher BMI may predict deeper olfactory fossa in women but not in men. These findings suggest expansion of weak points in the skull base as precursors to the development of SCSF leaks in response to elevated CSF pressures, particularly in women.

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The endoscope has revolutionized the diagnosis and treatment of diseases of the nose and paranasal sinuses. Endoscopic sinus surgery (ESS), like all minimally invasive surgery, is designed to combine an excellent outcome with minimal patient discomfort. Successful outcome with minimal complications can only be achieved with good knowledge of the endoscopic anatomy, appropriate training in the procedure and the understanding of the anatomical variations. The intraoperative complications of ESS are bleeding and injury to surrounding structures commonly the orbital structures and fovea ethmoidalis. This is a hospital based prospective observational study with an objective to define the distribution of Keros classification of the depth of olfactory fossa and its asymmetrical distribution rates based on Keros type. Prospective study in a tertiary rural based hospital. 100 patients above the age of 10 years from October 2013 to March 2015 for a period of one year six months undergoing endoscopic sinus surgery in the Department of ENT, P.E.S. Institute of Medical Sciences and Research, Kuppam were chosen randomly. The data was collected from these patients who will met the inclusion criteria of the study and before undergoing endoscopic sinus surgery by subjecting them to CT scan of paranasal sinuses. It is observed that a total of 100 patients had been studied in which the mean age of the population is 36.65 + 13.36 years. Youngest patient was 12 years old and eldest patient was 70 years old. Among the patients 50(50%) were males and remaining 50(50%) were females with a female to male ratio is 1:1. In the present study, the depth of olfactory fossa ranged from 2.1 to 8.3 mm inclusive of both sides in 200 CT images with a mean height of 5.21 mm. Of the 200 sides measured, the distribution of Keros classification is as the following-Keros type I 39(19.5%), Keros type II 143(71.5%) and Keros type III 18(9%) sides. Based on these observations, type II is the most common Keros type prevalent followed by type 1 Keros type and the least prevalent is the type III Keros type in the studied population. In the present study, on considering sides separately, the right side olfactory fossa depth ranged from 2.1 to 8.3 mm with a mean height of 5.43 mm and the left side olfactory fossa depth ranged from 2.1 to 8.1 mm with a mean height of 4.98 mm. On the right side, of 100 sides measured, the distribution of Keros classification is as the following-Keros type I 19(19%), Keros type II 68(68%) and Keros type III 13(13%) sides. On the left side, of 100 sides measured, the distribution of Keros classification is as the following-Keros type I 25(25%), Keros type II 70(70%) and Keros type III 5(5%) sides. Based on these observations, type II is the most common Keros type prevalent followed by type 1 Keros type and the least prevalent is the type III Keros type in the studied population on both sides. In the present study, out of 100 patients 23 patients were having asymmetric olfactory fossa between right and left sides based on Keros type, where as remaining 77% had symmetric Keros type on right and left sides. Out of 23 patients, 16 patients were having lower or deep olfactory fossa on right side, where as remaining 7 patients were having lower or deep olfactory fossa on left side. Based on these observations, a lower or deep ethmoid roof occurred more frequently on the right side than on the left side. Wilcoxon matched pair signed rank test is applied to see the significant difference between depth of right and left olfactory fossae. Since P value is < 0.001 the depth of olfactory fossa is significantly different from each other. The present study presents a precise, quantitative analysis of the olfactory fossa and ethmoid roof position as well as individual asymmetry. This information may be useful during pre-operative evaluation of CT images, as well as intraoperatively. The surgeon's understanding of the anatomy of a patient's ethmoid roof and its possible variations is crucial for countering possible complication risks during endoscopic sinus surgery.