Analysis of Ethmoid Roof and Skull Base With Coronal Section Paranasal Sinus Computed Tomography Cemil Gu ¨ler, MD,* l ˙ smail O ¨ nder Uysal, MD,* Kerem Polat, MD,* l ˙ smail S ¸alk, MD,Þ Togay Mu ¨derris, MD,þ and Mehmet l ˙ lkay Kos ¸ar, MD§ Abstract: Chronic paranasal sinus disease is one of the most com- mon causes of application to physicians in pediatric and adult patients. In the surgical treatment of these diseases, endoscopic sinus sur- gery is an application that is often done to increase the quality of the patient’s life. On account of this, the anatomic variations in skull basement must be well known to avoid possible major complications that may occur during the operation. Recent developments in paranasal sinus surgery also enhanced the need for examining exhaustively the anatomy of this region and existing pathology. Superiority of computed tomography (CT) has an unquestionable importance for the evaluation of anatomic struc- ture and pathology compared with conventional radiographs. A likely anatomic knowledge is needed for a safe surgery. Before the surgery, determining the anatomic variations makes the operation safer and increases the prospects, so we can prevent complications that may occur during the surgery. In this study, CT coronal sections of 300 patients who were ad- mitted to the Department of Ear Nose Throat of Medical Faculty of Cumhuriyet University Research and Training Hospital between the dates December 2008 and January 2011 with complaints of nasal flow and postnasal drip were studied. According to coronal section CT examinations, the patients were divided into 2 groups. Group 1, with 156 cases (64%), showed mucosal changes, and in 144 cases (36%), no mucosal changes were established (group 2). In comparison between the sexes, in groups 1 and 2 females, significant difference was determined for other parameters except the average height of the ethmoid roof. In the comparison between the sexes, in groups 1 and 2 males, significant difference was determined for all parameters. The difference between these 2 rates was statistically significant. Keros types 1 and 2 cases were compared with the control group, and there was no statistically significant difference. Notwithstand- ing, at the comparison of the Keros type 3 with the control group, there was a statistically significant difference for all the parameters (maximum orbital height, the length of the middle concha, and the nasal wall). It seems to be important for us to know the average length of the peripheral anatomic structures to avoid serious complications that may occur during the operation. Careful preoperative review of para- nasal sinus CT scans in patients undergoing sinus surgery seems to be the most important to prevent severe intraoperative complications. Key Words: Ethmoid roof, Keros classification, computed tomography (J Craniofac Surg 2012;23: 1460Y1464) E ndoscopic sinus surgery (ESS) is an operation with the objec- tive of gaining reduction to the sinus drainage pathways by re- moving or returning to normal the pathologies on them caused by the anatomic defects. With better understanding of the importance of mucociliary activity in the paranasal sinuses and introducing the endoscopy and computed tomography (CT), today this surgery is preferred as an alternative popular and successful treatment method especially for the treatment of chronic rhinosinusitis cases resistant to the maximal medical treatment. 1 Showing consideration to the functional anatomy and a mi- croinvasive surgery should be targeted during the surgical applica- tions. This goal enables the impaired drainage and ventilation of the paranasal sinuses to return to normal function and the secondary infections in these sinuses to heal by removing of the obstruction, stenosis, and pathological tissue in osteomeatal complex in the meatus nasi medius, the junction of the mucociliary flow from frontal, max- illary, and ethmoid sinuses. This indicates the importance of this region during the surgery. 2 There are several cadaver studies that analyzed the ethmoid roof. The most important one among these was presented by Keros, who classified the relationship between the ethmoid roof and crib- riform into the following 3 categories: Keros type 1: Olfactory sulcus is 1 to 3 mm deep, and the lateral lamella across the sulci is short. A significant part of the frontal bone supports the ethmoid roof, making the roof thick and the sinus operation less dangerous. Keros type 2: Olfactory sulcus is 3 to 7 mm deep, and the lateral lamella constitutes a large portion of the roof. Keros type 3: Olfactory sulcus is 8 to 16 mm deep, and the ethmoid roof is located on well above the cribriform plate. Here, the thin lateral lamella constitutes a much larger portion of the roof, and this part of the roof is devoid of the support from the frontal bone. This makes the surgery in such a type of sinuses the most dangerous 3 (Fig. 1). FIGURE 1. Keros classification. A, Type 1. B, Type 2. C, Type 3. ANATOMICAL STUDY 1460 The Journal of Craniofacial Surgery & Volume 23, Number 5, September 2012 From the Departments of *Otolaryngology, †Radiology, Cumhuriyet Uni- versity Medical School, Sivas; ‡Department of Otolaryngology, Ankara Training and Research Hospital, Ankara; and §Department of Anatomy, Cumhuriyet University School of Medicine, Sivas, Turkey. Received February 10, 2012. Accepted for publication March 24, 2012. Address correspondence and reprint requests to l ˙ smail O ¨ nder Uysal, MD, Cumhuriyet U ¨ niversitesi Tıp Faku ¨ltesi, Sivas, Turkey; E-mail: dr.iuysal@hotmail.com The authors report no conflict of interest. Copyright * 2012 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0b013e31825755b2 Copyright © 2012 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.