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Radiological anatomy of frontal sinus

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Radiological anatomy of frontal sinus

  1. 1. Radiological anatomy of Frontal sinus Balasubramanian Thiagarajan drtbalus otolaryngology online 1
  2. 2. Introduction Highly complex and variable anatomy Variations – impact on drainage Efficiency of muco-ciliary clearance – relationship to morphology of frontal sinus drtbalus otolaryngology online 2
  3. 3. Embryologydrtbalus otolaryngology online 3
  4. 4. Embryology - contd Continuation of embryonic infundibulum, frontal recess superiorly Upward migration of anterior ethmoid air cells Penetration via inferior aspect of frontal bone between the two tables Pneumatization 2-9 years Complete – 9 years drtbalus otolaryngology online 4
  5. 5. Frontal sinus drainage Expands into the diploic space of frontal bone from frontal sinus ostium Each sinus grows independently of the other Growth is dependent on ventilation, drainage, growth of surrounding sinuses and skull base Drainage is hence highly variable drtbalus otolaryngology online 5
  6. 6. Frontal sinus drainage - contd Inferomedially into funnel shaped area (frontal sinus ostium) Anterior wall of drainage channel is bounded by nasal beak Ostium is oriented perpendicular to the posterior wall of the sinus at the skull base level drtbalus otolaryngology online 6
  7. 7. Frontal beakdrtbalus otolaryngology online 7
  8. 8. Frontal sinus drainage pathway compartments Drainage pathway is divided into superior and inferior compartments Superior compartment is formed by union of adjacent air cells at the antero inferior portion of ethmoid bone Size and shape of this component varies with the varying anatomy for fronto ethmoidal air cells Superior compartment communicates with the inferior compartment drtbalus otolaryngology online 8
  9. 9. Inferior component This passage is really narrow This compartment is formed by ethmoidal infundibulum / middle meatus This is dependent on the attachment of uncinate process drtbalus otolaryngology online 9
  10. 10. Inferior compartmentInferior portion - infundibulum Inferior portion - infundibulum drtbalus otolaryngology online 10
  11. 11. Attachment to lamina papyracea – inferior component formed bymiddle meatus drtbalus otolaryngology online 11
  12. 12. Inferior compartment formed by infundibulum drtbalus otolaryngology online 12
  13. 13. drtbalus otolaryngology online 13
  14. 14. Frontal beakFrontal beak forms the floor of frontal sinus drtbalus otolaryngology online 14
  15. 15. Frontal recess Antero superior portion of ethmoidal air cell system This is where the frontal bone pneumatization begins Lateral wall is formed by lamina papyracea Medial wall is formed by vertical attachment of middle turbinate Posterior wall is variable ? Bulla if it manages todrtbalus otolaryngology online base reach up to skull 15
  16. 16. Frontal recess drtbalus otolaryngology online 16
  17. 17. Agger nasidrtbalus otolaryngology online 17
  18. 18. Large bulla Can obstruct frontal sinus outflow This area should be critically studied during imaging Causes obstruction from behind drtbalus otolaryngology online 18
  19. 19. Bulladrtbalus otolaryngology online 19
  20. 20. Uncinate vs frontal sinus drainage Uncinate – skull base attachment causes frontal sinus to drain into superior portion of ethmoidal infundibulum Uncinate – attached to middle turbinate causes frontal sinus to drain into ethmoidal infundibulum Uncinate – attached to lamina papyracea causes frontal to drain into superior aspect of middle meatus. Ethmoidal infundibulum ends in terminal recess drtbalus otolaryngology online 20
  21. 21. Ethmoidal infundibulum  3 – d space  Lateral – LP  Anteromedial – Uncinate  Posterior - Bulla drtbalus otolaryngology online 21
  22. 22. Frontal recess blockLarge agger cell causing narrowing of frontal recess drtbalus otolaryngology online 22
  23. 23. drtbalus otolaryngology online 23
  24. 24. uncinate process attached to skull base. The frontalrecess is seen between the agger nasi and uncinateprocess drtbalus otolaryngology online 24
  25. 25. Scan showing uncinate process being attached to laminapapyracea. This causes terminal recess to form. Frontalsinus drains directly into middle meatus drtbalus otolaryngology online 25
  26. 26. scan shows the uncinate process being attached to themiddle turbinate. Note the presence of infundibulumbetween the bulla and the uncinate process. Frontal sinus isseen opening into the infundibulum drtbalus otolaryngology online 26
  27. 27. Bents classification of frontal cell variants Type I: Single frontal recess cell above the agger Type II: Tier of air cells above agger projecting into the frontal recess Type III: Single massive air cell above agger expanding in superior direction Type IV: Single isolated cell within frontal sinus. Difficult to visualize due to thin walls drtbalus otolaryngology online 27
  28. 28. Type I & II frontal cell drtbalus otolaryngology online 28
  29. 29. Type IIIdrtbalus otolaryngology online 29
  30. 30. Type IVdrtbalus otolaryngology online 30
  31. 31. Supraorbital air cells Pneumatization of orbital plate of frontal bone Posterior to frontal recess & lateral to frontal sinus Sometimes can reach high up mimicking frontal sinus drtbalus otolaryngology online 31
  32. 32. Thank youdrtbalus otolaryngology online 32