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Normal anatomy & anatomical variations of PNS in CT are discussed in detail...

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  1. 1. By Dr.K.PRASANNA Radiology Resident RMMCH
  4. 4.  Bony part & cartilaginous part covered by muscle & skin  Cartilaginous part – upper & lower lateral cartilages, lesser alar cartilages & septal cartilage  Nasal skin  Internal nose divided into the Right and left by the nasal septum
  5. 5.  NASAL CAVITY PROPER  Roof – Nasal bone, sphenoid & ethmoid bone  Floor - Palatine process of the maxilla & Palatine bone  Medial wall  Lateral wall
  6. 6.  Mainly by both Internal & external carotid, both on the septum & lateral walls  Anterior & posterior ethmoidal artery  Sphenopalatine artery  Septal branch of greater palatine  Septal branch of superior labial artery
  7. 7.  Formed by bony, soft tissue & cartilage  Bony –  Ethmoid infundibulum & uncinate  Perpendicular plate of palatine bone  Medial plate of pterygoid process of sphenoid bone  Medial surfaces of lacrimal bones and maxillae  Inferior conchae
  8. 8.  Cartilage – In external nose, the lateral wall of cavity is supported by cartilage (lateral process of septal cartilage & major, minor alar cartilage)
  9. 9.  Marked by three bony projections, they extend medially across the nasal cavity separating the nasal cavity into for air channels – the turbinates or conchae  Superior ,middle & inferior tubinates or conchae. The conchae do not extend forwards into the external nose  The air space below and lateral to each turbinate is called as meatus  Superior, middle & inferior meatus & sphenoethmoidal recess  Middle Meatus – much significant
  10. 10. Superior Meatus – Limited only to posterior one third of lateral wall. Posterior ethmoidal sinus opens into it. Middle Meatus Inferior Meatus – Runs along the whole length of lateral wall. Nasolacrimal duct opens in its anterior part. Largest of all meatus Sphenoethmoidal recess – Above the superior turbinate. It receives the opening of sphenoid sinus
  11. 11.  Infundibulum – Air passage connecting the maxillary sinus ostium to middle meatus  Hiatus Semilunaris – Gap between the uncinate process and bulla ethmoidalis. Medially it communicates with middle meatus. Laterally & inf it communicates with infundibulum
  12. 12.  Frontal sinus – Opens into the anterior part of hiatus semilunaris  Maxillary sinus – Opens into the posterior part of hiatus semilunaris  Anterior and middle ethmoidal cells – Opens into the upper margin bulla ethmoidalis
  13. 13. SINUSES
  14. 14.  Air containing cavity in certain skull bones  Develop as a diverticula/outpouching from the lat wall of nose & extend into Maxilla, Ethmoid, sphenoid and frontal bones  Four sinuses – Maxillary, Frontal, Ethmoid (Ant & Post) & Sphenoid  Some sinuses are well developed & asymmetrical
  15. 15. Each sinuses have orifices that open into the meatus, covered by turbinates
  16. 16. Clinically - two groups Anterior – Frontal, Maxillary, Ant.Ethmoidal Posterior – Post Ethmoidal, Sphenoid
  17. 17.  Significance  Lighten the skull & facial bones  Contributes to vocal resonance  Collapsible framework that helps the brain to protect from blunt trauma  EPITHELIUM  They are lined by mucosa similar to that of the nasal cavity – pseudo stratified ciliated columnar epithelium  Epithelium contains – Mucinous & serous glands  Mucoperiosteum
  18. 18. Sinuses Status at Birth First Radiological evidence Reaches Adult size by Maxillary sinus Present at birth 4-5 months after birth 15 years Ethmoid sinus Present at birth 1 year 12 years Sphenoid sinus Not Present 4 years 15 years – adult age Frontal Sinus Not Present 6 years Size increases until teens
  19. 19.  Largest paranasal sinus  Pyramidal in shape  Base - towards lateral wall of nose  Apex – towards zygomatic process of maxilla
  20. 20.  Present at birth as a rudimentary sinus  First radiological evidence is at 4-5 months after birth  Reaches adult size by 15 years  On average, it has capacity of 14.75 ml (14-15)
  21. 21. • Facial surface of maxilla and cheek Ant wall • Infra temporal & pterygopalatine fossa Post wall • Middle & inferior meatuses (this wall is thin & membranous) Med wall • Floor of orbits Roof • Alveolar part of maxilla Floor
  22. 22.  DRAINAGE – OSTIUM  Seen high up in the medial wall  Does not open directly into the nasal cavity, but opens into post. part of ethmoidal infundibulum, via hiatus semilunaris into middle meatus.  The infundibulum is the air passage that connects the maxillary sinus ostium to the middle meatus.  Unfavourable for natural sinus drinage  Accessory ostium – 30 % cases
  23. 23.  Arterial supply – Maxillary artery, infra orbital, facial & greater palatine  Venous supply – anteriorly by facial vein & post.by maxillary vein  Nerve supply – infra orbital, anterior, middle & posterior superior alveolar nerves  Lymph nodes – cervical nodes & submandibular nodes
  24. 24.  Situated between the outer & inner table of frontal bone  Funnel shaped  Two sinuses on either side  Asymmetrical  Intervening bony septum which may be thin or deficiency
  25. 25.  Not present at birth  First radiological evidence is at 6 years  Reaches adult size after puberty  The natural frontal sinus ostium is usually located in the posteromedial floor of the sinus (most dependent part).  It opens into the middle meatus  The ethmoidal infundibulum can act as a channel for carrying the secretions (and infection) from the frontal sinus to anterior ethmoid cells and the maxillary sinus or vice versa.
  26. 26.  They develop from a variable site, their drainage will be either via an ostium into the frontal recess or via a nasofrontal duct into the anterior infundibulum. The opening or duct can be distorted by expansion of adjacent ethmoid cells  Boundaries  Ant wall – Skin over the forehead  Post wall - Meninges & the frontal lobe of brain  Inferior wall - orbit & its contents
  27. 27.  FRONTAL RECESS  The frontal recess is an hourglass like narrowing between the frontal sinus and the anterior middle meatus through which the frontal sinus drains. It is not a tubular structure, as the term nasofrontal duct might imply, and therefore the term recess is preferred.
  28. 28.  The frontal recesses are the narrowest anterior air channels and are common sites of inflammation. Their obstruction subsequently results in loss of ventilation and mucociliary clearance of the frontal sinus
  29. 29.  AGGER NASI CELL  Anterior, lateral, and inferior to the frontal recess is the agger nasi cell. It is aerated and represents the most anterior ethmoid air cell, usually lying deep to the lacrimal bone.  It usually borders the primary ostium or floor of the frontal sinus, and thus its size may directly influence the patency of the frontal recess and the anterior middle meatus.
  30. 30.  The frontal sinus can pneumatize both the vertical and the horizontal (orbital) plates of the frontal bone. The deepest area of the vertical portion of the sinus is near the midline at the level of the supraorbital ridge, and the medial sinus floor and the caudal anterior sinus wall are thinnest in this area. As a result, the sinus is best approached for a trephination at this level
  31. 31.  There is a rich sinus venous plexus (Breschet’s canals) that communicates with both the diploic veins and the dural spaces.  Arterial supply – supra orbital & supra trochlear  Venous supply – superior opthalmic vein  Lymph – Submandibular lymph node  Sensory innervation – supra orbital & supra trochlear
  32. 32.  Occupies the body of sphenoid  Right & left, seperated by a thin strip of bony septum (like frontal sinus)  Ostium opens into spheno ethmoidal recess  Relations of the sinus are very important, esp during the surgical approach of pituitary gland
  33. 33.  Relations –  Anterior part –  Roof – olfactory tract, optic chiasma & frontal lobe  Lateral – optic nerve, internal carotid artery & maxillary nerve  Posterior part  Roof – Pituitary gland in sella turcica  Lateral – Cavernous sinus,ICA & Cranial nerves III, IV, VI & all divisions of V
  34. 34.  Thin strips of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above  The pituitary gland can be surgically approached through the roof of the nasal cavities by passing first through the anteroinferior aspect of the sphenoid bone and into the sphenoidal sinuses and then through the top of the sphenoid bone into the hypophyseal fossa
  35. 35.  Thin walled air cavities in the lateral masses of the ethmoid bone  Varies from 3 – 18  Occupy the space between the upper third of the lateral nasal wall and the medial wall of orbit  Clinically divided into anterior ethmoidal air cells & posterior ethmoidal air cells, by basal lamella (lateral attachment of middle turbinate to lamina papyracea)
  36. 36.  DRAINAGE: Anterior - a recess of hiatus semilunaris & middle meatus via ehmoid bulla Post- sup.meatus & spenethmoidal recess.  Present at birth  Reaches adult size by 12 years  First radiological evidence seen at 1 year
  37. 37. Relations  Roof – formed by the anterior cranial fossa  Lateral wall - orbit  Medial wall – nasal cavity  Thin paper like bony part of the ethmoid separating the air cells from the orbit, called lamina papyracea, can be easily destroyed leading to spread of ethmoidal infections into the orbit  Optic nerve forms a close relationship with the posterior ethmoidal cells & is at risk during ethmoidal surgery
  39. 39.  The osteomeatal complex is the key anatomic area addressed by endoscopic sinus surgeons. Blockage of the osteomeatal complex prevents effective mucociliary clearance, thus leading to a stagnation of secretions and therefore leading to recurrent or chronic sinusitis.
  40. 40.  The OMC is bounded  medially by the middle turbinate,  posteriorly and superiorly by the basal lamella, and  laterally by the lamina papyracea.  Inferiorly and anteriorly the OMC is open.
  41. 41.  This anatomic region therefore includes  Maxillary sinus ostium  ethmoid bulla  frontal recess  uncinate process  infundibulum  hiatus semilunaris  middle meatus.
  43. 43.  Paradoxic Curvature  Normally, the convexity of the middle turbinate bone is directed medially, toward the nasal septum.  When paradoxically curved, the convexity of the bone is directed laterally toward the lateral sinus wall.  The inferior edge of the middle turbinate may assume various shapes, which may narrow and/or obstruct the nasal cavity, infundibulum, and middle meatus.
  44. 44.  Concha Bullosa  It is an aerated turbinate, most often the middle turbinate.  Less frequently, superior & inferior turbinate aeration can occur.  When the pneumatization involves the bulbous segment of the middle turbinate, the term concha bullosa applies.  If only the attachment portion of the middle turbinate is pneumatized, and the pneumatization does not extend into the bulbous segment, it is known as a lamellar concha.
  45. 45.  Other Variations  Additional variations of the middle turbinate can occur, including medial & lateral displacement, lateral bending, L shape, and sagittal transverse clefts  Medial displacement – due to other middle meatal structures (i.e., polypoid disease, pneumatized uncinate process) encroaching upon the middle turbinate.  Lateral displacement - due to the compression of the turbinate toward the lateral nasal wall by a septal spur or septal deviation.
  46. 46.  The nasal septum deviation may compress the middle turbinate laterally, narrowing the middle meatus and the presence of associated bony spurs may further compromise the OMU.  Obstruction, secondary inflammation, swollen membranes, and infection can occur
  47. 47.  DEVIATION  The course of the free edge of the uncinate process may either extend slightly obliquely toward the nasal septum, with the free edge surrounding the inferoanterior surface of the ethmoid bulla, or it extends more medially to the medial surface of the ethmoid bulla. If the free edge of the uncinate is deviated in a more lateral direction, it may cause narrowing or obstruction of the hiatus semilunaris and infundibulum.
  48. 48.  Attachment  Attachment to the lamina papyracea, the lateral surface of the middle turbinate, or the fovea ethmoidalis in the floor of the anterior cranial fossa may occur.  If the uncinate process attaches to the ethmoidal roof or middle turbinate, during uncinatectomy, traction could inadvertently damage the ethmoid roof and result in CSF rhinorrhea or other intracranial complications.
  49. 49.  Sometimes the free edge of the uncinate process adheres to the orbital floor, or inferior aspect of the lamina papyracea. This is referred to as an atelectatic uncinate process
  50. 50.  Pneumatization  The pneumatization of the uncinate process is believed to be due to extension of the agger nasi cell within the anterosuperior portion of the uncinate process.  Functionally, the pneumatized uncinate process resembles a concha bullosa or an enlarged ethmoid bulla.
  51. 51.  Infraorbital ethmoid cells are pneumatized ethmoid air cells that project along the medial roof of the maxillary sinus and the most inferior portion of the lamina papyracea, below the ethmoid bulla and lateral to the uncinate process
  52. 52.  Two definitions of Onodi cells.  The first defines them as the most posterior ethmoid cells, being superolateral to the sphenoid sinus and closely associated with the optic nerve.  Another, more general description defines Onodi cells as posterior ethmoid cells extending into the sphenoid bone, situated either adjacent to or impinging upon the optic nerve
  53. 53.  Its appearance varies considerably, based on the extent of pneumatization.  Extensive pneumatization may obstruct the ostiomeatal complex.  Elongated ethmoid bullae are usually in a superior to inferior direction rather than in an anterior to posterior direction.  So, Relatively unlikely to obstruct the ostiomeatal complex.
  54. 54.  Encountered rarely  extends into the lesser wing and the anterior and posterior clinoid processes  Can lead to distortion of optic cannal configuration
  55. 55.  May be either congenital or the result of prior facial trauma.  It occur most often at the site of the insertion of the basal lamella into the lamina papyracea, thus rendering this portion of the lamina papyracea most delicate  Orbit at risk
  56. 56.  When aeration of the normally bony crista galli occurs the aerated cells may communicate with the frontal recess, and obstruction of this ostium.  To avoid unnecessary surgical extension into the anterior cranial vault, it is important to recognize an aerated crista galli and differentiate it from an ethmoid air cell.
  57. 57.  Air cells are commonly found within the posterosuperior portion of the nasal septum and, when present, communicate with the sphenoid sinus.  As a result, any inflammatory disease that occurs within the paranasal sinuses may also affect these cells
  58. 58.  It is important to note any asymmetry in the height of the ethmoid roof.  Intracranial penetration during surgery is more likely to occur on the side where the position of the roof is lower
  60. 60.  X RAY  CT  MRI
  61. 61.  X ray – Water’s view & caldwell view  Ct – gold standard. Coronal & axial sections  MRI is predominantly used for pre and post operative management of naso sinus malignancy  The chief disadvantage of MRI is its inability to show the bony details of the sinuses, as both air and bone give no signal
  63. 63.  CT is currently the modality of choice in the evaluation of the paranasal sinuses and adjacent structures.  Its ability to optimally display bone, soft tissue, and air provides an accurate depiction of both the anatomy and the extent of disease in and around the paranasal sinuses.  In contrast to standard radiographs, CT clearly shows the fine bony anatomy of the osteomeatal channels.
  64. 64.  There are few pre requisites in few situations  a course of adequate medical therapy to eliminate or diminish reversible mucosal inflammation.  pretreatment with a sympathomimetic nasal spray 15 minutes prior to scanning in order to reduce nasal congestion (mucosal edema) and thus improve the display of the fine bony architecture and any irreversible mucosal disease
  65. 65.  Coronal & axial views  The coronal plane best shows the ostiomeatal unit (OMU), shows the relationship of the brain to the ethmoid roof.  Coronal plane should be the primary imaging orientation for evaluation of the sinonasal tract in all patients with inflammatory sinus disease who are endoscopic surgical candidates
  66. 66.  Prone with chin hyperextended  Gantry anglutaion- perpendicular to hard palate  Section thickness-3mm contigous  Table increment- 3-4 mmeach step  Kvp-125  Mas-80  Hanging head technique
  67. 67.  HEAD HANGING METHOD  Performed in the prone position, so that any remaining sinus secretions do not obscure the OMU  In patients who cannot tolerate prone positioning (children, patients of advanced age, etc.), the hanging head technique can sometimes be utilized.
  68. 68.  In this technique, the patient is placed in the supine position and the neck is maximally extended.  A pillow placed under the patient’s shoulders facilitates positioning.  The CT gantry is then angled to be perpendicular to the hard palate.  It is not always possible to obtain true direct coronal images with this technique
  69. 69.  Axial images complement the coronal study, particularly when there is severe disease (opacification) of any of the paranasal sinuses and surgical treatment is contemplated.  The axial studies provide the best CT evaluation of the anterior and posterior sinus walls  Axial images are particularly important in visualizing the frontoethmoid junction and the sphenoethmoid recess.
  70. 70.  CT axial section of PNS - image
  71. 71.  Whenever there is total opacification of the frontal, maxillary, or sphenoid sinuses, a complete axial and coronal CT examination should be performed.  And also, if the patient has a suspected neoplasm, a complete axial and coronal examination need to be performed to provide the most detailed analysis of the sinonasal cavities and the adjacent skull base
  72. 72.  IMAGING PLANE : REIDS’S LINE – runs b/w infraorbital margin (IOM line) & EAM. (parallel - axial) ALEXANDER’S LINE – perpendicular to reids line. (perpendicular - coronal)
  73. 73.  Contrast is not required for all cases of CT paranasal sinus  Used in cases such as vascular lesion, malignancy, mass extending intra cranially, acute infections