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Sinus anatomy and variants

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seminar on CT PNS

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Sinus anatomy and variants

  1. 1. Paranasal Sinuses Anatomy & Variants- A Systematic Approach To Imaging Before FESS Dr Priyanka Vishwakarma
  2. 2. Four Paired Sinuses – • Ethmoid • Maxillary • Frontal • Sphenoid • The sinuses develop as outgrowths from the nasal cavity; hence they all drain directly or indirectly into the nose
  3. 3. Meati • superior meatus drains the posterior ethmoid air cells and the sphenoid sinus via the sphenoethmoidal recess • middle meatus drains the frontal sinus via the nasofrontal duct/frontal recess, the maxillary sinus via the maxillary ostium, and the anterior ethmoid air cells via the ethmoid cell ostia. • The nasolacrimal duct drains into the inferior meatus • spheno-ethmoidal recess, above and posterior to the superior concha, receives the opening of the sphenoidal sinus
  4. 4. Osteomeatal unit Common Drainage Pathway Of The Ant. Group of Sinuses.-Coronal scan The osteomeatal unit (OMU) includes the • uncinate process • Ethmoid infundibulum • Ethmoid Bulla • Middle Meatus • Hiatus Semilunaris Most common site of inflammatory disease
  5. 5. Nasal Septum • Commonest Variation-DNS • Pneumatization • Inferior Turbinate-Hypertrophy
  6. 6. Maxillary sinus • Largest and most constant pns. • Pyramidal in shape- base is usually medial, with its apex in the zygomatic process of the maxilla • Base -lat nasal wall-ostium • Posterior wall/Temporal- pterygomaxillary fossa • Roof -Formed by roof of the orbit- infra orbital foramen containing the infra orbital vessels and nerves • Ant-maxilla facial surface
  7. 7. Variants Related To the maxillary Sinus Concha bullosa Paradoxical curvature of MT Haller Cell Septae Dehiscent floor-1st ,2nd Molar Infn
  8. 8. Concha Bullosa •pneumatization of the bulbous portion of the middle turbinate •An enlarged concha bullosa may impede drainage from the middle meatus
  9. 9. Haller cells • Ethmoidal air cells belonging to the anterior ethmoidal group. • Also known as the infra orbital cells • Adhere to roof of maxillary sinus forming the lat wall of infundibulum • Enlargement of these cells can impede the maxillary sinus drainage
  10. 10. Paradoxical curvature- can potentially narrow or obstruct the infundibulum or middle meatus.
  11. 11. bony septum in the maxillary sinuses (MS)
  12. 12. Ethmoidal sinus • basal lamellae of the middle turbinate separates the ethmoid into anterior and posterior groups with different drainage patterns • Ant cells form 1st followed by the posterior cells.They are not seen on radiographs until age one • Lateral wall-Formed by the orbital plate of the ethmoid,known as the lamina papyracea.this wall could be dehiscent- route of spread of infection
  13. 13. . The transition of thick fovea to the thin portion of roof of ethmoid medially is very weak-injuries during surgery leading on to CSF leak.
  14. 14. Ethmoids-ant and post
  15. 15. vertical attachment of basal lamellae to anterior skull base
  16. 16. Related Variants • A cell above the orbit is called a supraorbital cell.found in 15% of pt • Invasion of an ethmoid cell into the floor of the frontal sinus is called a frontal cell(type 1-4)
  17. 17. Agger Nasi Cell term Agger in Latin - Mound/Eminence. • anterior to the antero superior attachment of the middle turbinate and borders the frontal recess. • its size may directly influence the patency of the frontal recess. These agger nasi cells are commonly involved in the pathogenesis of the formation of frontal • mucocele. • It is the 1st prominent anatomical landmark encountered in FESS
  18. 18. ethmoid bulla • superior to uncinate processes. • Ethmoid bulla air cells are part of the anterior ethmoid sinuses and make up the superior border of the hiatus semilunaris. • variable pneumatization.
  19. 19. Onodi Cells • posterior ethmoidal cells extending supero lateral to the sphenoid sinus & can either abut to or impinging upon the optic nerve. • When these Onodi cells abut or surround the optic nerve, the nerve is at risk when surgical excision of these cells is performed. • It is also a potential cause of incomplete sphenoidectomy.
  20. 20. Olfactory fossa • The depth of the olfactory fossa is determined by the height of the lateral lamella of the cribriform plate, which is part of the ethmoid bone. In 1962, Keros had classified the depth of the olfactory fossa into three types, that is, • Keros type I: <3 mm, • type II: 4-7 mm , and • type III: 8-16 mm.-Kero type III is most vulnerable to iatrogenic injury.
  21. 21. Keros type I-< 3 mm
  22. 22. Keros type II- 4 to 7 mm
  23. 23. Keros type III-6-18 mm
  24. 24. Frontal sinus • different sizes, are separated by a bony septum that is usually deviated to one side • Asymmetry btw the two sinuses frequent • It may be absent in 5% of cases • Best seen on Saggital images • Among the para nasal sinuses this sinus shows the maximum variations.
  25. 25. • The post wall separates the frontal sinus from the anterior cranial fossa and is much thinner. • Floor is formed by the upper part of the orbits • Frontal sinus appear very late in life. Infact they are not seen in skull films before the age of 6. • Nasofrontal duct-misnomer • Frontal Recess
  26. 26. • the frontal recess can be conceptualized as an inverted funnel within the anterior ethmoid complex through which the frontal sinus drains. • The tip or apex of the funnel lies at the frontal sinus ostium, -sagittal CT images as a “waist” located at the level of the nasofrontal process. • The frontal recess typically flares out inferiorly and posteriorly to form the wider opening of the funnel. • inferior portion of the frontal sinus (commonly referred to as the frontal infundibulum) + the frontal ostium + frontal recess = frontal sinus outflow tract
  27. 27. the right frontal recess (dotted red line), which is bounded anteriorly and laterally by an agger nasi cell (white arrow) and a type 1 frontal cell (black arrow), medially by the middle turbinate
  28. 28.    posteriorly by the ethmoid bulla and bulla lamella. The nasofrontal process (arrowhead in b) forms the floor of the frontal sinus and demarcates the level of the frontal sinus ostium
  29. 29. superior compartment of the FSDP
  30. 30. Frontal outflow tract shows conglomeratization of air cells. Types of frontal sinus air cells include: • I – Type I frontal cell (a single air cell above agger nasi) • II – Type II frontal cell (a series of air cells above agger nasi but below the orbital roof) • III – Type III frontal cell (this cell extends into the frontal sinus but is contiguous with agger nasi • cell) • IV – Type IV frontal cell lies completely within the frontal sinus
  31. 31. Type 2 frontal cells  
  32. 32. Type 3 frontal cell
  33. 33. Type 4 frontal cell situated entirely within the right frontal sinus & bordered by the anterior frontal sinus wall. The type 4 cell does not abut the agger nasi cell.
  34. 34. Variants – obstruct FSDP • Agger nasi • Supraorbital cells
  35. 35. •Frontal recess is bounded anteriorly by agger nasi cell and posteriorly by suprabullar air cell- can compromise frontal sinus drainage pathway.
  36. 36. Supraorbital/suprabullar ethmoid cell
  37. 37. Pneumatized crista galli may communicate with the frontal recess and can potentially obstruct the frontal sinus ostium
  38. 38. Inter–frontal sinus septal cell arises from the frontal sinus septum
  39. 39. Fess Failure • Frontal sinusitis after FESS
  40. 40. • The uncinate process may be attached to: • Lamina papyracea or agger nasi (lamina terminalis). The frontal recess opens directly into middle meatus,medial to UP The lamina terminalis is the blind pouch between the UP and lamina papyracea • Skull base or middle turbinate. The frontal recess drains into the ethmoid infundibulum lateral to UP • Orbital floor or inferior aspect of the lamina papyracea (silent sinus syndrome, atelectatic uncinate process). This variant is associated with hypoplastic, ipsilateral
  41. 41. Sphenoidal sinus • They remain undeveloped until age three.By age seven the pneumatisation has reached the sell turcica.By age 18 the sinuses have reached full size • Optic nerve and internal carotid arteries traverse its lateral wall. • Pneumatisation can extend as far as the clivus,the sphenoid wings and the foramen magmum
  42. 42. •sphenoid sinus (SpS) and the sphenoethmoidal recess marked by the (*). •(AE: anterior ethmoid, PE: posterior ethmoid, CC: carotid canal, NS: nasal septum)
  43. 43. •(FR: foramen rotundum, • VC: vidian canal, •OC: optic canal, • AC: anterior clinoid, • PtP: pterygoid plate)
  44. 44. sphenoethmoidal recess
  45. 45. variations of intersinus septum • 1.A single midline intersinus septum extending on to the anterior wall of sella. • 2. Multiple incomplete septae may be seen • 3. Accessory septa may be present. These could be seen terminating on to the carotid canal or optic
  46. 46. 3 types Concal-children-5% presellar-23% Sellar-67%
  47. 47. Pneumatized lateral recesses of sphenoid sinus (SpS) and foramen rotundum (FR) bulging into the sinus
  48. 48. pneumatized pterygoid plates
  49. 49. FESS-a roadmap to the otorhinolaryngologist prior to surgery. There are two main questions that the radiologist should address: 1. Are there anatomic features on the computed tomography (CT) scan that predispose the patient to impaired mucociliary clearance? 2. Are there anatomic features that pose a surgical hazard?
  50. 50. Checklist-Systematic • the extent of sinus opacification, • patency of sinus drainage pathways, • anatomic variants(obstruct drainage pathways &limit Surgical access), • critical variants, (CP,LP,SphS dehiscence)and • condition of soft tissues of the brain, neck, and orbits.-extrasinus extent of the disease
  51. 51. References • http://www.ajronline.org/doi/full/10.2214/AJR.0 • http://dx.doi.org/10.1148/rg.291085118

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