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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
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
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
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
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
Frontal beakFrontal beak forms the floor of frontal sinus drtbalus otolaryngology online 14
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
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
uncinate process attached to skull base. The frontalrecess is seen between the agger nasi and uncinateprocess drtbalus otolaryngology online 24
Scan showing uncinate process being attached to laminapapyracea. This causes terminal recess to form. Frontalsinus drains directly into middle meatus drtbalus otolaryngology online 25
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
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
Type I & II frontal cell drtbalus otolaryngology online 28
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