CT anatomy of paranasal sinuses.

Transcription

1 CT anatomy of paranasal sinuses. Poster No.: C-2117 Congress: ECR 2017 Type: Educational Exhibit Authors: O. Dib, H. Chahinez, B. Asma, C. abdelouahab, M. Ourrad El, B. Nacereddine ; Algiers/DZ, 16000/DZ, Alger/DZ Keywords: Anatomy, Ear / Nose / Throat, CT, Education, elearning, Education and training DOI: /ecr2017/C-2117 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 64

2 Learning objectives To recall the normal anatomy of paranasal sinuses. To know anatomic variations of paranasal sinuses. To have a systematic way in looking for these variations in a CT scan. Background 1.The paranasal sinuses are the frontal, ethmoid, sphenoid and maxillary sinuses, housed within the bones of the skull (figure 1). All sinuses open into the lateral wall of the nasal cavity through their corresponding ostia (figure 2). The lateral wall of nasal cavity has three projections of bone called superior, middle and inferior nasal conchae. The space below each concha is called a meatus. Inferior meatus: receives opening of lower end of nasolacrimal duct. Middle meatus: Lies below the middle concha, It has a rounded swelling called bulla ethmoidalis, which open on its upper border. Hiatus semilunaris is a curved opening lying just below the bulla and receives opening of maxillary sinus. Infundibulum is a funnel-shaped channel at anterior end of hiatus. Superior meatus receives openings of posterior ethmoid sinuses. Sphenoethmoidal recess: is a small area above superior concha and receives the opening of sphenoid air sinus. 2.The aim of nasal and paranasal sinuses imaging is to provide a surgical road map describing the anatomy, defining the obstructive lesions, and noting the anatomical factors that may predispose impaired mucociliary clearance and per operative complications. 3.The CT scan is the gold standard investigation in all sinus diseases, when performed it allows to identify: Obstruction of the drainage pathways or anatomic variants that may compromise already narrow drainage pathways. Identification of critical anatomic areas where anatomic variants pose special risks during sinus surgery. Page 2 of 64

3 Local extension of disease. Complications. 4.How to perform a CT imaging? Medical treatment should be given before CT scan to reduce transient acute inflammatory or infectious mucosal changes. Anatomy is adequately assessed without the use of IV injected ionated contrast material. The acquisition is accomplished in supine position with 1mm thick overlapping axial slices (figure 3). Coronal, sagittal or oblique reformations are helpful for a good interpretation (figure 4). Images for this section: Page 3 of 64

4 Fig. 1: Figure 1. Anatomic representation of paranasal sinuses Page 4 of 64

5 Fig. 2: Figure 2. Coronal and sagittal CT slices showing the paranasal sinuses drainage pathways. Page 5 of 64

6 Fig. 3: Figure 3. CT scan acquisition in supine position from the top of the frontal sinuses to bottom of the alveolar process of the maxillary sinus ( red arrow), with a 1mm thick axial slices. Fig. 4: Figure 4. Axial, coronal and sagittal planes are helpful for a good interpretation of a paranasal sinuses CT scan. Page 6 of 64

7 Findings and procedure details A/ CT anatomy: 1. Ostiomeatal unit: It is a complex anatomic region at crossroads of mucociliary drainage from frontal, anterior ethmoid sinuses and maxillary sinuses. Components of anterior osteomeatal unit are (figures 5, 6): Maxillary ostium: drainage channel of maxillary sinus. Infundibulum: common channel that drains the ostia of maxillary and ethmoid sinuses to the hiatus semilunaris. Uncinate process: hook like process that arises from posteromedial aspect of nasolacrimal duct and forms the anterior boundary for hiatus semilunaris. Ethmoid bulla: usually a single air that projects inferomedially over hiatus semilunaris. Hiatus semilunaris: final drainage passage, region that between ethmoid bulla superiorly and free edge of uncinate process. Uncinate process (UP): The uncinate process, is the most important structure of the ostiomeatal unit. The UP prevents the direct contact of the inspired air with the maxillary sinus, acting like a shield, and plays a role in mucociliary activity. The UP is a thin, semi-circular bony process of variable length and covered with the mucosa. It is a thin curved bony lamina of variable height from the lateral side of the ethmoid labyrinth, that forms a portion of the lateral nasal wall. It has different attachments (figure 8): Inferior attachment to the neck of the inferior turbinate. Supero-anterior attachement to lamina papyracea in 50%. Postero-lateral attachment to the roof of the maxillary sinus. Page 7 of 64

8 Anterior attachment of the uncinate process. Ethmoid bulla: Ethmoid bulla is the most posterior of all anterior ethmoid air cells. It is the roof of the hiatus semilunaris and posterior ethmoid infundibulum. The relationship of ethmoid bulla with lamina paprisea in lateral, and the relationship of frontal cranial fossa in superior with base should be clarified in preoperative CT (figure 9). The degree of pneumatization may be highly variable (figure 10), from a giant ethmoid bulla that pushes the UP medially to torus ethmoidalis without pneumatization. Middle turbinate It attaches superiorly to the cribriform plate (medial lamella). It attaches posteriorly and laterally to the lamina papyracea: basal(ground) lamella (figure 11). It lies inferomedially to the anterior ethmoidal air cells. Anterior: oriented in sagittal plate and it is vertically attached to the cribriform plate. Middle: oriented in frontal plate and it is attached to the lamina papyracea or basal lamella laterally; it separates anterior and posterior ethmoids (figure 12). Posterior: oriented in horizontal plate and it's attached to the perpendicular plate of palate. Different sizes of middle turbinate may be seen (figure 13). Frontal recess It's bordering anatomical structure forming the walls of the passage from frontal sinus to the middle meatus. It is not strictly a duct but a channel located between anterior ethmoid cells. It is the space posterior to the frontal beak (nasal process of the frontal bone), between the lamina papyracea and the vertical lamella of the middle turbinate continuing on to the lateral wall of the olfactory fossa and is anterior to the basal lamella of the middle turbinate (figure 14). Frontal sinus ostium The frontal ostium is defined as the narrowest area of the transition zone from the frontal sinus to the frontal recess with its anterior edge formed by the frontal sinus beak and Page 8 of 64

9 the posterior edge formed by the skull base (best seen on the parasagittal computed tomography [CT] scan) (figure 13). The lateral boundary of the frontal ostium is the lamina papyracea and the medial boundary, the upward extension of the vertical lamella of the middle turbinate and lateral wall of the olfactory fossa. Sphenoethmoidal recess The sphenoethmoidal recess, also called the posterior ostiomeatal unit, drains the posterior sinuses (posterior ethmoidal and sphenoid) (figure 15). Olfactory fossa: It is a variable depression seen in cribriform plate that medially bounded by perpendicular plate and laterally by lateral lamella. Lateral lamella is the point of structural weakness in the anterior skull base. The fovea ethmoidalis is a part of the frontal bone that separates the ethmoidal cells from the anterior cranial fossa. The fovea ethmoidalis also medially connects with the lateral lamella of the cribriform plate (Figure 18). Anterior ethmoid foramen: It is a small opening in the ethmoid bone and transmits the anterior ethmoid artery and nerve. It is the anatomical border for anterior and posterior ethmoid air cells in coronal plate (figure 19). B/ Anatomic variants: Anatomical variations are which damage the normal functional drainage pathways and increase the risk of surgeries. Identification of these anatomic variants of paranasal sinus helps the surgeons to access sites of diseases which are extremely difficult. Deviated nasal septum: The nasal septum may be focally deviated inferiorly at the chondro-vomeral junction or have a more broad based curvature. It is most of the time associated with asymmetry of the adjacent turbinates (figure 20). Page 9 of 64

10 Septal spurs is a generally asymptomatic bone deformity that may cause restriction of the nasal air flow, it may be associated with septal deviation, which makes surgical access difficult and narrow the middle meatus or ethmoid infundibulum (figure 21). Septal spurs are frequently encountered at the junction of the perpendicular plate of the ethmoid and the vomer. Middle turbinate: Concha bullosa is a variation originated from pneumatization of the bone plate by extension of ethmoid sinus cells. Such variation may be either uni- or bilateral (figure 22). Varied degrees of pneumatization of the concha may be observed, possibly causing middle meatus or infundibulum obstruction, besides being related to deviation of the nasal septum to the contralateral side (figure 23). Paradoxical turbinates occur as the convexity of the middle turbinate is directed towards the medial wall of the maxillary sinus (figure 24). Depending on the degree of curvature of the paradoxical turbinate; compression of the infundibulum and sinusal obstruction may be observed. Pneumatized superior turbinate;in some cases the pneumatization may happen in the superior turbinate (figure 25). Uncinate Process (UP) variations Variations of the superior attachment of the uncinate process : Landsberg and Friedman described six different types related to the position of the superior attachment of UP and presented more detailed information relating to the superior attachment, by an imaging technique (Figures 26, 27). The variability of the UP's anterosuperior attachment affects the drainage of the frontal recess. The most common superior attachment of uncinate process is to the lamina papyraceae followed by the attachement to the agger nasi air cell anteriorly, in these two cases the frontal recess is drained into the middle meatus. UP can be attached to the middle concha, this causes the frontal recess to move toward the agger nasi posteriorly. Rarely the skull base can be reached and the frontal recess can be drained Into the ethmoid infundibulum. Page 10 of 64

11 Uncinate bulla The aeration of UP is called uncinate bulla (figure 28). This variation increases the wideness of the uncinate, so it constitutes to be potentially dangerous for the infundibulum. It can act like a concha bullosa or a widened ethmoid bulla. Deviation of the tip of the uncinate The UP can show lateral deviation, obstructing infundibulum and/or semilunar hiatus or medial deviation, affecting the middle meatus (figure 29). According to John Earwaker, six (06)Types of ostiomeatal complex abnormalities can be encountered depending on the deviation of the UP and the type of the ethmoid bulla (figure 30). Atelectatic UP Sometimes, UP's free end shows hypoplastic development and attaches to orbit medial wall or inferior section of lamina paprisea. This condition is called atelectatic UP. Generally, it is seen together with an opacified hypoplastic maxillary sinus. Frontal sinus The frontal recess is the space into which the frontal sinus drains. This space is usually occupied by a number of cells that affect the direction and position of this drainage pathway. A consensus classification (IFAC) which allows more precise naming based on the position of the cells as well as how these cells affect the frontal drainage pathway, has been established (table 1). Agger nasi cells (ANC): The most constant and anterior of ethmoid air cells. It is located anterior to the vertical attachment of middle turbinate to the skull base. Forms the floor of the frontal recess. It reaches the lacrimal fossa inferiolaterally, and is anterolaterally arched by the nasal bone (figures 31, 32). Page 11 of 64

12 A large agger nasi can impige on and distort the frontal recess. The posterior-medial wall usually gives rise to the anterior uncinate process. Supra agger cell (SAC): SAC sits above the ANC behind the beak of the frontal bone (figure 33). In this classification a SAC may be a single cell or consists of a number of cells sitting above the ANC and may affect the frontal drainage pathway depending as to whether it is situated medially or laterally. Supra agger frontal cell (SAFC): This cell does not extend significantly into the frontal sinus but occupies a portion of the floor of the frontal sinus (figures 34, 35). Supra bullar cell Suprabullar cell (SBC) is the cell sitting directly above the bulla eth- moidalis and the anterior wall of the SBC almost in continuity with the anterior face of the bulla ethmoidalis (figure 36). Supra bulla frontal cell SBFC is a pneumatization through the frontal ostium into the frontal sinus, with the skull base forming the posterior wall of the cell and the cell the cell pushes the frontal sinus drainage pathway anteriorly (figure 37). Supra orbital ethmoid cell (SOEC) The SOEC takes its origin from around and above the anterior ethmoid artery. The cell is seen to pneumatize over the orbit, making this an SOEC rather than an SBFC. Frontal septal cell The cell can be seen originating from the region of the interfrontal sinus septum and occupying a significant part of the frontal drainage pathway, pushing this pathway laterally and often posteriorly (figure 39). The cell sitting higher in the frontal sinus and narrowing the frontal sinus drainage pathway as the frontal sinus transitions into the frontal recess. Infra orbital cells (Haller cells): Page 12 of 64

13 Haller cell is located inferiorly and anteriorly to the ethmoid bulla, and grow into the floor of the orbit, adjacent to the natural ostium of the maxillary sinus, which may narrow the maxillary sinus ostium (figure 40). Maxillary sinus: The anatomic variations of maxillary sinus are common findings in CT. It can exhibit anatomic variations such as: antral septa, pneumatization, hypoplasia, exostosis and variations in location of the arteries. Maxillary sinus septations: Maxillary sinus septa are thin walls of cortical bone present within the maxillary sinus, with variable number, thickness and length. often extends from the infra orbital canal to the lateral wall (figure 41). The maxillary sinus pneumatization: Four recesses have been described, as follows (figures 42, 43): The palatine recess that extends inferomedially to the hard palate towards the midline. The alveolar recess, closely related to the molar and premolar teeth roots. The infraorbital recess, projecting anteriorly along the roof of the maxillary sinus. The zygomatic recess that extends over the malar bone at variable distances. Protrusion of the ION into the maxillary sinus: The infraorbital nerve arises from the maxillary branch of the trigeminal nerve and normally traverses the orbital floor in the infraorbital canal. Sometimes, however, the infraorbital canal protrudes into the maxillary sinus separate from the orbital floor (figure 44). Onodi cell: The Onodi cell has been defined by the Anatomic Terminology Group as being the most posterior ethmoid air cell that pneumatizes superiorly and laterally to the sphenoid sinus and which is in intimate relation to the optic nerve. The posterior ethmoid cells were classified into four types depending on their relation to the optic nerve canal as follows (figures 45, 46, 47 & 48): Type A: no contact observed between the wall of the ethmoid cell and optic nerve canal. Page 13 of 64

14 Type B: the ethmoid cell wall being adjacent to the wall of the optic nerve canal at a maximum distance of 2 mm (as measured in the axial and sagittal planes), but not extending laterally or supero-laterally. Type C: the ethmoid cell wall being adjacent the optic nerve canal wall at a distance greater than 2 mm in the axial and/or sagittal planes extending laterally or supero-laterally without any bulging of the optic nerve canal into the ethmoid bone. Type D: the ethmoid cell wall being adjacent the optic nerve canal wall at a distance greater than 5mm (as measured in the axial or sagittal plane), extending supero-laterally with optic nerve bulging. This bulging being defined as a protrusion of the optic nerve into the ethmoid cell visualized in at least two planes. Sphenoid sinus: Pneumatization of the sphenoid sinus: The lateral walls are thin bony layers and can be divided into two areas: an anterior orbital area and the posterior cranial area. This wall has immediately adjacent to it highly important structures such as the internal carotid artery, optic nerve and the cavernous sinus. The relations of the sphenoid sinus with structures around are close when the sinus is well pneumatized. When this happens, the surrounding vessels and nerves are seen in the sinus cavity as irregularities or ridges. Pneumatization of the sphenoid sinus can extend to further from its body, and into all of its parts, such as the clinoid processes, greater wings and pterygoid planes (figure 49). The sphenoid sinus may pneumatize the anterior clinoid processes, which can encroach the optic nerve (figure 50). The pneumatization of the pterygoïd processes is an extension of the sinus between the maxillary nerve and the nerve of the pterygoïd canal (Vidian nerve), this extension could reach the posterior part of the maxillary sinus (figure 51). Intersinus septation of sphenoid: The sphenoid sinuses are asymmetric cavities inside the sphenoid body separated by a bony septum, this septum is very often deviated laterally to one side or the other, it is common that it inserts on the carotid canal or the optic canal. Page 14 of 64

15 More often than not, the sphenoid cavity is divided by more than one septa (figure 52). According to Fernandez- Miranda JC et al. (2009), at least one of the septa is inserted on the carotid canal in 87% of cases. ICA bulges into sphenoid sinus: The internal carotid artery is the most medial element of the cavernous sinus, and it lies in direct relation to the lateral wall of the sphenoid sinus. Depending on the pneumatization of the sphenoid, the impression of the internal carotid artery may be barely noticeable or highly noticeable (figure 53). We may have a bulging of the internal carotid artery or in some cases, the thin bone usually covering the internal carotid artery is dehiscent, leaving the artery exposed to the sinus cavity (figure 54). Hypoplasia or aplasia of the sphenoid sinus Vulnerability of the anterior skull base: The thin lateral lamella of cribriform plate and low Ethmoid Skull Base (ESB) are potential anatomical variants that can lead to iatrogenic injuries in the form of direct penetration trauma to the Dura, serious intracranial and intra-cerebral complications during ESS. Keros classified the depth of the olfactory fossa into 3 types based on the height of the lateral lamella (figure 56). The depth of the olfactory fossa is 1-3 mm in Type I, 4-7 mm in Type II, and 8-16 mm in Type III. According to Keros, the greater the height of the lateral lamella, the higher the risk of its penetration into the anterior cranial fossa. The Keros type III is the most vulnerable one, considering the major risk for iatrogenic lesion of the lateral lamella of the cribriform plate. Ethmoidal roof asymmetry Asymmetry in the anterior of the skull base and especially in the ethmoid roof is important for ethmoid sinus surgery. Ethmoid roof asymmetry is a frequent anatomical variation that may occur as a result of the association of differences in the height of the lateral lamella and/or contour of the ethmoidal roof, with angulation of the lateral lamella (figure 57). Page 15 of 64

16 Images for this section: Fig. 5: Figure 5. Coronal and sagittal CT slices showing the ostiomeatal unit ( red circle), with the middle meatus (yellow line) between the uncinate process laterally and the medal turbinate medially. Page 16 of 64

17 Fig. 6: Figure 6. Coronal CT slice showing the components of the ostiomeatal unit Page 17 of 64

18 Fig. 7: Figure 7. Coronal CT slice showing the drainage passage components in the ostiomeatal unit. Page 18 of 64

19 Fig. 8: Figure 8. Coronal and sagittal CT images showing the different attachments of the uncinate process (in red) A.Inferior attachment to the neck of the inferior turbinate. B. Supero-anterior attachement to lamina papyracea in 50%. C. Postero-lateral attachment to the roof of the maxillary sinus (C': sagittal plane). D. Anterior attachment of the uncinate process (sagittal plane). Orange circle: ethmoid bulla. Page 19 of 64

20 Fig. 9: Figure 9. Coronal and sagittal CT images showing the ethmoid bulla (EB). EB forms the roof of the hiatus semilunaris (A and B). Anterior ethmoid cells can drain into the middle meatus via the ethmoid bulla (C and D). Page 20 of 64

21 Fig. 10: Figure 10. Coronal CT images illustrating different types of the bulla ethmoidalis. Fig. 11: Figure 11. Coronal CT images showing the superior ans posterolateral attaches of the middle turbinate (in blue). red circle (ethmoid bulla). Page 21 of 64

22 Fig. 12: Figure 12. Sagittal CT image showing the superior attachment of the middle turbinate (in blue), dividing the ethmoid cells into anterior and posterior ethmoid cells. Fig. 13: Figure 13. coronal CT images showing the different size variations of middle turbinate. Page 22 of 64

23 Fig. 14: Figure 14. Sagittal and coronal CT images showing the different parts of the frontal recess. Fig. 15: Figure 15. Axial and sagittal slices showing posterior ethmoid (green arrow) and sphenoid sinus (red arrow) drainages, in superior meatus. Page 23 of 64

24 Fig. 16: Figure 16. Sagittal and coronal images showing the different components of the nasal septum. Page 24 of 64

25 Fig. 17: Figure 17. Coronal image and three different axial images of the nasolacrymal duct (yellow circle). Page 25 of 64

26 Page 26 of 64

27 Fig. 18: Figure 18. Coronal CT image showing the olfactory fossa ( white asterisk) and the ethmoidal roof components. Fig. 19: Figure 19. Coronal image and axial cut in the level of the anterior ethmoidal artery. This artery exits the orbit through the anterior ethmoidal foramen and enters the olfactory fossa at the point of attachment of the middle turbinate to the cribriform plate. Page 27 of 64

28 Fig. 20: Figure 20. A. Axial and coronal CT images showing nasal septum deviation towards right side with asymmetry of the middle turbinates.b. most of the time nasal septum deviation is associated with asymmetry of the adjacent turbinates. Fig. 21: Figure 21. A and B. axial and coronal CT images showing nasal septum deviation towards left side, with septal spur. C. This spur is frequently seen at the junction of the perpendicular plate of the ethmoid and the vomer (yellow circle). Page 28 of 64

29 Fig. 22: Figure 22. Coronal, axial and sagittal CT images showing bilateral pneumatization of middle concha. Page 29 of 64

30 Fig. 23: Figure 23. Coronal and axial CT images showing showing right concha bullosa with deviation of nasal septum towards left side. Notice that a large concha bullosa, may obstruct the drainage pathway of the antrum by distorting the UP and narrowing the infundibulum. Page 30 of 64

31 Fig. 24: Figure 24. coronal CT images showing in (A) Normal configuration of the turbinates ( convex configuration medially "Yellow curve"). In (B) Paradoxical turn of middle turbinate, associated with septal deviation and septal spur, which may impair access to the osteomeatal unit. Fig. 25: Figure 25. Coronal CT image showing enlargement of the superior turbinates due to pneumatization. Page 31 of 64

32 Fig. 26: UP Classification Fig. 27: Figure 27. Coronal CT images illustrating different types of the superior uncinate process insertion according to Landsberg & Friedman classification. Notice that attachment to the lamina papyracea allows the frontal drainage in the medial meatus, attachment to the skull base allows frontal drainage into the ethmoid infundibulum and attachment to the neck of the middle turbinate allows frontal drainage into the ethmoid infundibulum or into an anterior ethmoid cell. Page 32 of 64

33 Fig. 28: Figure 28. Coronal CT image showing a right uncinate bulla (red circle), narrowing the right ethmoid infundibulum. Page 33 of 64

34 Fig. 29: Figure 29. Coronal CT images showing lateral deviation of the right uncinate processes, which may obstruct the ethmoid infundibulum. Page 34 of 64

35 Fig. 30: Figure 30. Types of ostiomeatal complex abnormalities Page 35 of 64

36 Fig. 31: Figure 31. Coronal and sagittal CT scan demonstrating a single Agger nasi cell (ANC). This CT scan demonstrates how the ANC sits directly behind the frontal process of the maxilla. This ANC wih the suprabullar cell narrow the frontal recess. Page 36 of 64

37 Fig. 32: Figure 32. Coronal and sagittal CT scan showing a single ANC. Page 37 of 64

38 Fig. 33: Figure 33. Coronal and sagittal CT scan images demonstrating a supra agger cell (SAC). Associated in case 'A' with Supra bullar and supraorbital ethmoid cells and in cases 'B'and 'C' with supra bullar cells Page 38 of 64

39 Fig. 34: Figure 34. Axial and sagittal CT scan images showing an example of a small SAFC in which the frontal sinus is well pneumatized with a small beak. Page 39 of 64

40 Fig. 35: Figure 35. Coronal and sagittal CT scan images showing bilateral SAFC. These cells are laterally based and pneumatizing through the frontal ostium into the frontal sinus and pushing the drainage pathway of the frontal sinus medially. Page 40 of 64

41 Fig. 36: Figure 36. CT scan showing the classical supra bullar cell (SBC), associated en case 'A' with an agger nasi cell, and in case 'B' with, supra bulla frontal and supraorbital ethmoid cells Page 41 of 64

42 Fig. 37: Figure 37. Coronal and sagittal CT scan images illustrating the SBFC pushing the frontal sinus drainage pathway anteriorly until it touches the SAFC. Again the pathway becomes an anteromedial pathway (Red line). Fig. 38: Figure 38. Sagittal and coronal CT images showing pneumatization over orbit seen on the coronal and parasagittal CT scans (supra orbital ethmoid cell (SOEC)). Page 42 of 64

43 Fig. 39: Figure 39. Axial and coronal CT images illustrating a frontal septal cell narrowing the frontal sinuses drainage pathways. Page 43 of 64

44 Fig. 40: Figure 40. Coronal CT scan image showing bilateral infra orbital cells, which impair the maxillary sinuses drainage. Page 44 of 64

45 Fig. 41: Figure 41. Axial and coronal CT images demonstrating bony septation within the maxillary antrum. These septas extend from the infra orbital canal (green arrow). Page 45 of 64

46 Fig. 42: Figure 42. Coronal and axial CT scan images illustrating in 'A' and 'B' maxillary sinus pneumatization of alveolar recesses ( with protrusion of roots of the premolar and molar teeth; red circle), in 'C' pneumatization of the infra orbital recesses. Page 46 of 64

47 Fig. 43: Figure 43. Coronal and axial CT scan images, illustrating in red line in 'A' the palatine recess and in 'B' zygomatic recess. Page 47 of 64

48 Fig. 44: Figure 44. Axial(A), right parasagittal(b), and coronal (C) sinus CT images show unilateral right-sided protrusion of the ION into the maxillary sinus (green arrow). While part of the wall of the left IOC protrudes into the sinus. Page 48 of 64

49 Fig. 45: Figure 45. CT scan sagittal image of the optic nerve canal observed for type A(protrusion of the optic nerve into the sphenoid sinus, no Onodi cell). Page 49 of 64

50 Fig. 46: Figure 46. CT scan sagittal image of the optic nerve canal observed for type B in sagittal plane. Page 50 of 64

51 Fig. 47: Figure 47. CT scan images of the optic nerve canal observed for type C in respectively sagittal and coronal planes. Page 51 of 64

52 Fig. 48: Figure 48. CT scan images of the optic nerve observed for type D(protrusion of the optic nerve into the Onodi cell) in respectively axial, sagittal and coronal planes. Page 52 of 64

53 Fig. 49: Figure 49. Sagittal and coronal CT sections showing pneumatization of the sphenoid sinus. In 'A' of infraclival and septal, in 'B' pterygoid process, in 'C' infraclival. Page 53 of 64

54 Fig. 50: Figure 50. Coronal CT scan image illustrating a pneumatization of the right anterior clinoid process encroaching right optic nerve. Page 54 of 64

55 Fig. 51: Figure 51. Axial, sagittal and coronal CT scan images illustrating pneumatisation of the left pterygoid process and protrusion of the vidian nerve(green line) within the left sphenoid sinus. Page 55 of 64

56 Fig. 52: Figure 52. Two Axial CT scan images showing multiple septa in a large sphenoid sinus. Note that one of septa is inserted on the carotid canal (red circle). Page 56 of 64

57 Fig. 53: Figure 53. Axial CT scan image showing a bulging of the internal carotid arteries in sphenoid sinuses Page 57 of 64

58 Fig. 54: Figure 54. Coronal and sagittal CT scan images showing dehiscence of the internal carotid arteries into sphenoid sinuses. Page 58 of 64

59 Fig. 55: Figure 55. Effect of hypoplastic or aplastic sphenoid sinus Page 59 of 64

60 Fig. 56: Figure 56. Coronal CT scan images illustrating the depth of the olfactory fossae. In 'A' not very deep olfactory fossae, where the ethmoidal roofs are almost in the same plane as the cribriform plate, corresponding to Keros type I. In 'B' olfactory fossae are deeper and lateral lamellas are longer, corresponding to Keros type II. In 'C' Olfactory fossae are very deep, lateral lamellas are long and thin, corresponding to Keros III. Page 60 of 64

61 Fig. 57: Figure 57. Coronal CT scan image showing an angulation of the ethmoid roof at right, with an increase in the angle between the lateral lamella and the horizontal portion of the cribriform plate. Page 61 of 64

62 Fig. 58: IFAC 2016 Page 62 of 64

63 Conclusion The paranasal sinuses have many different anatomical variations. Computed tomography (CT) scan plays a fundamental role in the diagnosis of anatomical variations. The identification of the anatomical variations helps the endoscopic surgeons to avoid major risks in approaching the vital anatomical structures. Personal information Dr DIB OTHMANE Hopital central de l'armée, Alger, Algérie References 1/An Analysis of the Anatomic Variations of the Paranasal Sinuses and Ethmoid Roof Using Computed Tomography ; Hatice Kaplanoglu1, Veysel Kaplanoglu2, Alper Dilli1, Ugur Toprak2, Baki Hekimo#lu1, Eurasian J Med 2013; 45: /Radiographic Analysis of the Ethmoid Roof based on KEROS Classification among Filipinos, Justin Elfred Lan B. Paber, MD1 Michael Salvador D. Cabato, MD2 Romeo L. Villarta, Jr, MD, MPH3 Josefino G. Hernandez, MD3, Philippine Journal of otolaryngology-head and neck Surgery Vol. 23 no. 1 January - June /The International Frontal Sinus Anatomy Classification (IFAC) and Classification of the Extent of Endoscopic Frontal Sinus Surgery (EFSS), International Forum of Allergy & Rhinology. 4/Anatomical Variations of Paranasal Sinuses on Coronal CT-Scan in Subjects with Complaints Pertaining to PNS International Journal of Anatomy, Radiology and Surgery. DOI: /IJARS/2016/21554:2192 5/Multiplanar Sinus CT:#A Systematic Approach to Imaging Before Functional Endoscopic Sinus Surgery Jenny K. Hoang1#James D. Eastwood1 Christopher L. Tebbit2 Christine M. Glastonbury3, AJR 2010; 194:W527-W536 6/CT of Anatomic Variants of the Paranasal Sinuses and Nasal Cavity: Poor Correlation With Radiologically Significant Rhinosinusitis but Importance in Surgical Planning AJR 2015; 204: Katya A. Shpilberg1 Simon C. Daniel1 Amish H. Doshi1 William Lawson2 Peter M. Som1 Page 63 of 64

64 7/Protrusion of the Infraorbital Nerve into the Maxillary Sinus on CT: Prevalence, Proposed Grading Method, and Suggested Clinical Implications X J.E. Lantos, A.N. Pearlman, X A. Gupta, X J.L. Chazen, R.D. Zimmerman, D.R. Shatzkes, and C.D. Phillips AJNR Am J Neuroradiol 37: Feb /The Onodi Cell and Optic Canal as Variations Assessed with Paranasal Sinus CT, Takahiro Kitamura1), Hironori Takebayashi2), Emi Maeda3), Ryosuke Koike4) and Takayuki Kawashima5), Pract. Otol. (Kyoto) Suppl. 144:42 ~ 43,2015 9/CT of Anatomic Variants of the Paranasal Sinuses and Nasal Cavity: Poor Correlation With Radiologically Significant Rhinosinusitis but Importance in Surgical Planning, Katya A. Shpilberg1 Simon C. Daniel1 Amish H. Doshi1 William Lawson2 Peter M. Som1, AJR 2015; 204: Normal 0 21 false false false FR X-NONE X-NONE Page 64 of 64