Imaging Analysis of Onodi Cells on Cone-Beam Computed Tomography

Original Researches Imaging Analysis of Onodi Cells on Cone-Beam Computed Tomography Ibrahim K. Ali1  http://orcid.org/0000-0002-3334-1317 Kaustubh Sansare1  Freny Karjodkar1  Mohd Saalim1  1Department of Oral Medicine and Radiology, Nair Hospital Dental College, Mumbai, India Abstract Introduction Onodi cells are the most posterior ethmoid air cells, and extend superolaterally to the sphenoid sinus. The identification of Onodi cells is essential to because they can have some significant anatomic variations and relationships to vital adjacent structures, like the optic canal, the sphenoid sinus, and the internal carotid artery. Objective The present study aimed to assess the prevalence of Onodi cells and their position with respect to sphenoid sinus. To the authors' best knowledge, this is the first study that uses cone-beam computed tomography (CBCT) to assess the prevalence and position of Onodi cells. Methods We collected CBCT scan records from November 1st, 2016, to July 31st, 2017; the patients who fulfilled the eligibility criteria were included in the present study. The CBCT scans were reviewed by two independent observers. The descriptive statistics was performed using the Statistical Package for the Social Sciences (SPSS, SPSS, Inc., Chicago IL, US) software, version 17.0. A cross-tabulation of gender with the presence and position of Onodi cells was evaluated using the Chi-squared (χ2) test. The inter- and intraobserver agreements were evaluated using Kappa (κ) statistics. Results Onodi cells were identified in 86 (42.8%) out of 201 patients. A subgroup analysis revealed that Onodi cells were present in 45 (43.3%) female and 41 (42.3%) male patients. The position of the Onodi cells was superior with respect to the sphenoid sinus in 43 (50%) of the patients, superolateral in 36 (41.9%), and lateral to the sphenoid sinus in 7 (8.1%) of the patients. Conclusion The present study indicated a high prevalence of Onodi cells, with approximately equal distribution among males and females, and mostly superior in position in relation to the sphenoid sinus. Keywords onodi cell; optic neuritis; cone-beam computed tomography; endonasal transsphenoidal technique Introduction Dr. Adolfo Onodi described Onodi cells as the most posterior ethmoid air cells that extend superolaterally to the sphenoid sinus, and are intimately related to the optic nerve. During sinus surgeries, unrecognized Onodi cells can result in serious damage to the optic nerve.1 2 Currently, there has been more concern to define these cells and their variations as they pertain to the endoscopic sinus and endonasal sellar surgery. The identification of Onodi cells is essential because they can have some significant anatomic variations and relationships to vital adjacent structures like the optic canal, the sphenoid sinus and the internal carotid artery. The endonasal transsphenoidal technique is the recent preferred approach for the resection of pituitary adenomas.3 This technique is chosen over the transcranial route due to its less invasive nature. As this procedure is gaining increasing popularity, it is imperative to unambiguously identify the surrounding anatomy to ensure a safe and precise dissection.4 During surgery, the identification of Onodi cells is crucial to maximize exposure and reduce the risk of injury to the surrounding structures.5 The prevalence of Onodi cells varies with different identification methods. Driben et al6 reported Onodi cell prevalence on cadaveric endoscopic examinations and axial section of computed tomography (CT) examinations that was of 39% and 7% respectively. Weinberger et al7 reported 14% and 8% of prevalence on cadaveric endoscopic versus coronal CT examinations respectively. Yeoh and Tan8 and Thanaviratananich et al9 reported prevalences of 51% and 60% respectively on Asian cadavers by performing endoscopic examinations. These studies reveal that the prevalence by endoscopy is higher than that by radiography. Arslan et al,10 Unal et al,11 and Nitinavakarn et al12 studied two views (axial and coronal) of CT scans and reported prevalences of 12%, 8% and 25% respectively. Bansberg et al13 and Batra et al14 reported a greater prevalence of Onodi cells when they examined three views of the CT in contrast with two views of the CT. Chmielik and Chmielik15 reported a prevalence of 39.8% of Onodi cells by examining three CT planes. The aforementioned studies reveal that when the scan data are viewed in all three planes, the radiographic prevalence improves. To overcome this low prevalence, the examination of these cells in different sections is recommended. Cone-beam computed tomography (CBCT) is a recent imaging modality that enables the visualization of Onodi cells in different planes with various advantages over computed tomography (CT). The literature search did not reveal any study investigating the prevalence of Onodi cells using CBCT. To the authors' best knowledge, the present is the first study that uses CBCT to assess the prevalence and position of Onodi cells with respect to the sphenoid sinus. Materials and Methods The CBCT scan records from March 2015 to February 2016 were retrieved from the digital imaging and communications in medicine archive folder of our institution. These scans had been used earlier in a study involving accessory maxillary ostium and Haller cells. The Z statistic was of 1.96 for the 95% confidence interval, 7% minimum allowable risk, power of 80% and the expected prevalence of 0.39 (39%) were taken from this previous study.15 The minimum sample size calculated was 189; therefore, we decided to include 201 CBCT scans from the archive folder that fulfilled the inclusion criteria. The CBCT scans were reviewed by two independent observers (radiologists with a minimum of 5 years of experience in interpreting scans). The subjects who had had trauma or had history of surgery in the sinus region, or tumor causing distortion of the anatomy, were excluded from the present study. The CBCT scans were taken using the Kodak CS 9300 3D system (Carestream Health, Inc., Rochester, NY, US) with field of view of 17 × 13.5 cm, Voxel size of 250 × 250 × 250 µm, 10 mA, X-ray pulse time of 30 ms, and 70 kVp. A training session to precisely identify Onodi cells was planned for the observers before the beginning of the study. The CBCT images were evaluated using a three-dimensional imaging communication software (Carestream Health, Inc., Rochester, NY, US) on a workstation with a 19-inchHP Compaq LE1911 LCD monitor (Hewlett-Packard, Palo Alto, CA, US). The scans were independently analyzed by the two observers, who were allowed to use the contrast and zoom tools. A total of 50 scans were reviewed twice at an interval of 15 days by the same observers to calculate intraobserver agreement using Kappa (κ) statistics. The descriptive statistics was performed (...truncated)